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What Was Earth Like During the Ice Age_ Science for Sleep · Night Science Stories

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  Speaker 1: Hi guys, welcome to Night Science Stories. Close your eyes
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  Speaker 1: if you like and let your breath find a slow
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  Speaker 1: and even rhythm. Tonight we will drift back through time
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  Speaker 1: to a quieter, colder Earth. We will step gently through
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  Speaker 1: the rooms of a long winter and see how light
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  Speaker 1: and orbit and ocean work together to paint glaciers on
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  Speaker 1: the continents and low tides across the world. I will
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  Speaker 1: speak softly as we move, and if you fall asleep
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  Speaker 1: along the way, the story will keep its pace without you.
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  Speaker 1: Imagine the planet not as a fixed picture, but as
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  Speaker 1: a breathing animal with a pulse that is measured in
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  Speaker 1: tens of thousands of years. There were many ice ages,
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  Speaker 1: not just one. The ice advanced and retreated like a tide.
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  Speaker 1: You can only see if you wait for a very
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  Speaker 1: long time. In those slow cycles, cold did not arrive
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  Speaker 1: with a shout. It gathered like frost on a window,
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  Speaker 1: first at the edges and then in quiet patterns that thickened.
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  Speaker 1: Summers cooled a little. Winters lengthened a little. Snow that
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  Speaker 1: fell in northern lands melted less than before. and over
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  Speaker 1: centuries small drifts became long fields of white. Where the
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  Speaker 1: snow lingered through the summer, it hardened under its own weight.
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  Speaker 1: Flakes became grains, grains became fern, and fern became glacier
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  Speaker 1: ice that flowed under gravity as if it were very
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  Speaker 1: slow honey. Glaciers do not look alive when you stand
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  Speaker 1: on one for an afternoon. But if you could watch
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  Speaker 1: for a thousand years, you would see them creep down valleys,
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  Speaker 1: chewing at the rock below, and you would see the
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  Speaker 1: snow line step lower year by year. In warm times,
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  Speaker 1: the same line would climb and the ice would slide
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  Speaker 1: backward like a tide in reverse. The rhythm that guides
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  Speaker 1: these changes begins with geometry. Earth does not go around
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  Speaker 1: the sun in a perfect circle. The orbit stretches and
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  Speaker 1: relaxes over very long times. The axis of Earth is
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  Speaker 1: tilted and that tilt leans a little more and a
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  Speaker 1: little less in a long sway. The axis also draws
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  Speaker 1: a slow circle in the sky, like a spinning top
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  Speaker 1: that does not fall. These motions change how sunlight is
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  Speaker 1: distributed across seasons and across latitudes. The total energy from
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  Speaker 1: the sun changes only a little, but the timing of
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  Speaker 1: that energy matters. If summer in the far north is
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  Speaker 1: a little weaker for many thousands of years, the snow
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  Speaker 1: from winter will not finish melting before the next winter arrives.
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  Speaker 1: A small imbalance repeated like this is enough to start
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  Speaker 1: a wide change. This is why the cycles are named
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  Speaker 1: for a person who realised that subtle changes in orbit
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  Speaker 1: could set the pace for ice. Sunlight on snow has
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  Speaker 1: its own habit. Fresh snow is bright. It throws most
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  Speaker 1: of the light back into the sky as snow and
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  Speaker 1: ice spread. More light returns to space and the ground
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  Speaker 1: and the air above the ground warm less than they
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  Speaker 1: did before. The planet becomes better at keeping the cold
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  Speaker 1: it already has. This is a feedback. It is like
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  Speaker 1: a whisper that turns into a chorus as more voices
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  Speaker 1: join in. When ice retreats, the opposite is true. Dark ground,
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  Speaker 1: dark water, and dark Forest tops absorb more light and
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  Speaker 1: the surface warms. The planet remembers where white once lay
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  Speaker 1: and responds when white leaves. Clouds play their part as well.
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  Speaker 1: Over ice they form and scatter light in particular ways
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  Speaker 1: that can make local mornings look like a pale pearl shell.
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  Speaker 1: Over dark water they tend to be thinner and let
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  Speaker 1: more light through. In high latitudes The angle of the
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  Speaker 1: sun is low for many months, and the brightness of
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  Speaker 1: snow and the softness of clouds work together to keep
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  Speaker 1: that light from sinking deeply into the ground. Air above
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  Speaker 1: the ice is not only colder, it is also different
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  Speaker 1: in what it holds. When the world cools, the large
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  Speaker 1: exchange between warm oceans and the atmosphere changes. In many
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  Speaker 1: glacial intervals, the air contained less carbon dioxide and less
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  Speaker 1: methane than during warm periods. That change was both a
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  Speaker 1: cause and a response. Lower greenhouse gases helped deepen the cold,
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  Speaker 1: and the cold altered the ways the ocean stored carbon
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  Speaker 1: and the ways wetlands breathed methane into the sky. Dust
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  Speaker 1: also became more common in many regions. Colder and drier
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  Speaker 1: climates left more bare soil and stronger winds that could
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  Speaker 1: lift fine grains. Those grains crossed oceans and fell on ice.
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  Speaker 1: Each layer of snow trapped a little of that dust
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  Speaker 1: and a little of the air of the day. When
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  Speaker 1: that snow turned to ice, it kept those gifts safe.
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  Speaker 1: Thousands of years later, people would read them like lines
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  Speaker 1: of a diary. In Greenland and Antarctica, the ice that
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  Speaker 1: fell as snow many years ago is still there, pressed
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  Speaker 1: into blue crystal. In the central parts of those ice caps,
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  Speaker 1: the snow does not melt, it only stacks. The weight
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  Speaker 1: squeezes air from between the grains until only small bubbles remain,
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  Speaker 1: and those bubbles keep the memory of ancient winds and
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  Speaker 1: the breath of ancient plants and seas. Scientists lower a
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  Speaker 1: hollow drill into the ice and bring up cylinders that
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  Speaker 1: are like tree rings in a different language. The ice
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  Speaker 1: itself holds the ratio of heavy oxygen to light oxygen,
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  Speaker 1: which reflects the temperature of the clouds that made the snow.
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  Speaker 1: The tiny bubbles hold the past concentration of gases. The
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  Speaker 1: dust trapped in the layers shows how windy and how
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  Speaker 1: dry the world was when that snow fell. Acids and
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  Speaker 1: salts record eruptions and sea spray. In some places, the
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  Speaker 1: record runs back for hundreds of thousands of years through
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  Speaker 1: several cycles of advance and retreat. When the cores are
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  Speaker 1: laid out by age, the curves of temperature and carbon
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  Speaker 1: dioxide rise and fall together with a grace that looks
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  Speaker 1: human only because we love patterns. In truth, it is
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  Speaker 1: the voice of water and light and air singing in
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  Speaker 1: long phrases. Turn your attention to the continents in the north.
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  Speaker 1: Picture a white sheet that spreads over Canada and into
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  Speaker 1: the northern United States. Picture another that rests across Scandinavia,
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  Speaker 1: Finland and a wide part of northwestern Eurasia. These were
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  Speaker 1: the great ice sheets of the north. They were not flat.
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  Speaker 1: They rose into domes that were kilometres high, so tall
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  Speaker 1: that the air above them was thin. and the wind
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  Speaker 1: made long trails of snow on their crowns. At their edges,
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  Speaker 1: they flowed outward in slow lobes that pressed against hills
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  Speaker 1: and wrapped around stubborn ridges. Where they met mountains, they
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  Speaker 1: climbed over passes and poured down valleys, smoothing the sides
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  Speaker 1: and deepening the floor. They plucked stones the size of
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  Speaker 1: houses and carried them without complaint. then dropped them far
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  Speaker 1: from their parent bedrock when the ice thinned. Those travellers
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  Speaker 1: are called erratics. They are signs of a time when
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  Speaker 1: rock could ride on water frozen into a single mass.
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  Speaker 1: Under the ice the ground sank. Rock behaves like a
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  Speaker 1: very stiff liquid over long times. Under the weight of
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  Speaker 1: the ice, it was pushed aside and down. A bulge
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  Speaker 1: rose just beyond the edge of the sheet as the
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  Speaker 1: displaced rock found somewhere to go. When the ice melted,
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  Speaker 1: the centre began to rise again and the bulge sank back. Today,
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  Speaker 1: shorelines in some places tilt because the land is still
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  Speaker 1: lifting from the old burdens. Rivers have quietly changed their
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  Speaker 1: paths to match this lift. Lakes formed in hollows scoured
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  Speaker 1: by the moving ice, and some of those lakes are
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  Speaker 1: long and deep and still fed by cold springs that
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  Speaker 1: find their way through the broken stones left behind. Walk
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  Speaker 1: with your mind to the far south. Over Antarctica, the
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  Speaker 1: ice did not only grow during cold times, it is
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  Speaker 1: a continent that carries a kingdom of ice even in
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  Speaker 1: warmer ages, a blanket that holds most of the fresh
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  Speaker 1: water on Earth. During deep glaciations, the winds around this
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  Speaker 1: frozen land were fierce, and sea ice extended far beyond
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  Speaker 1: the coast for many months. Around its edges, huge platforms
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  Speaker 1: of floating ice were thick enough to hold the weight
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  Speaker 1: of a marching seal or a patient penguin. Beneath some
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  Speaker 1: of those platforms, brine channels formed where salt made the
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  Speaker 1: water heavy and cold. In those channels, delicate crystals grew
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  Speaker 1: like upside-down flowers. Life found ways to feed in the shadows.
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  Speaker 1: In the cores taken from this ice, the presence of
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  Speaker 1: sea salts and tiny algae from ancient summers gives hints
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  Speaker 1: about how far the sea ice reached and how the
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  Speaker 1: seasons shifted. From the polar caps let us slip into
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  Speaker 1: the ocean. You can think of the world ocean as
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  Speaker 1: a slow conveyor of heat and salt. Warm water from
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  Speaker 1: low latitudes flows toward higher latitudes near the surface. It
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  Speaker 1: gives up heat to the air along the way, which
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  Speaker 1: is part of why some northern coasts are milder than
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  Speaker 1: you might expect. In certain places, the surface water grows
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  Speaker 1: cold and salty enough to sink. It falls into the
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  Speaker 1: depths and begins a long journey back toward the equator
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  Speaker 1: along the sea floor. This deep flow eventually rises in
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  Speaker 1: other basins where wind and the rotation of the planet
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  Speaker 1: draw it upward. The full circuit takes longer than a
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  Speaker 1: human memory. During glacial times, this conveyor was not the
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  Speaker 1: same as it is now, where sea ice spread. The
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  Speaker 1: water at the surface grew saltier as ice formed and
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  Speaker 1: rejected salt. That water could sink, but wind patterns also shifted,
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  Speaker 1: and in some periods the layers in the ocean were
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  Speaker 1: more clearly separated than today, with the deep waters holding
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  Speaker 1: more of the carbon that would otherwise have been in
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  Speaker 1: the air. Cold winds could also dust the surface with
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  Speaker 1: iron-rich particles that fed tiny ocean plants in places where
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  Speaker 1: iron was scarce. Those plants used carbon dioxide to grow,
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  Speaker 1: and when they died, some of the carbon sank with them.
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  Speaker 1: The ocean stored more breath than the sky. When glaciers grew,
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  Speaker 1: sea level fell. Water that became ice could not be
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  Speaker 1: in the ocean at the same time. At the peak
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  Speaker 1: of the last great cold time, the surface of the
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  Speaker 1: sea was lower by more than 100 meters compared with today.
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  Speaker 1: Imagine how far a shoreline can move when the sea
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  Speaker 1: steps down by that height. Wide shelves that are now
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  Speaker 1: underwater were then dry ground. Rivers did not end at
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  Speaker 1: the present beaches. They ran far out across those exposed plains,
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  Speaker 1: joining and braiding and carving new canyons into the outer
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  Speaker 1: edge of the shelf. You can see some of those
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  Speaker 1: buried canyons today in maps made with sonar. Long estuaries
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  Speaker 1: that we know now as bays were once river valleys
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  Speaker 1: with forests and meadows. Coastal caves that divers explore today
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  Speaker 1: were open to the air and felt the footsteps of
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  Speaker 1: animals and people. In the northwestern Pacific, a broad stretch
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  Speaker 1: of dry land appeared where there is now a strait.
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  Speaker 1: Two continents came close enough to touch, with no need
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  Speaker 1: for boats in most seasons. Low hills of tundra and
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  Speaker 1: grass connected what we call Siberia with what we call Alaska.
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  Speaker 1: This land is known by a name that holds the
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  Speaker 1: memory of a people, and it was not only a
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  Speaker 1: bridge for humans, it was a path for caribou and bison,
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  Speaker 1: for wolves and foxes, for small plants that chased a
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  Speaker 1: climate they could tolerate, for insects lifted by wind. In
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  Speaker 1: some places the ground was rich in bones, mammoth and
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  Speaker 1: horse and musk-oxen fell and froze and were covered by
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  Speaker 1: dust and snow and preserved in permafrost for a very
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  Speaker 1: long time. People do not walk in single lines in history,
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  Speaker 1: but the presence of this land made many routes possible.
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  Speaker 1: Some may have followed the inner corridor between ice sheets
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  Speaker 1: when it opened. Others may have followed the coast, walking
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  Speaker 1: beaches and headlands where kelp and shellfish could feed a
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  Speaker 1: small group that knew how to read tide and rock.
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  Speaker 1: To the south, in the tropics, the fall in sea
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  Speaker 1: level drew a different map. Where there are now many
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  Speaker 1: islands and narrow seas in Southeast Asia, there was once
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  Speaker 1: a large block of land, rivers that now have separate
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  Speaker 1: mouths joined into wide systems, that crossed plains and sank
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  Speaker 1: into large lakes. Forests expanded in some regions and narrowed
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  Speaker 1: in others as rainfall patterns moved. Farther to the southeast,
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  Speaker 1: the shallow seas that separate Australia from New Guinea and
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  Speaker 1: from what is now called Tasmania were mostly dry as well,
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  Speaker 1: except for channels that cut across in places and could
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  Speaker 1: be crossed when tides and winds were kind. All of
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  Speaker 1: this connected land is called by a name that blends
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  Speaker 1: two words. It was home to people who had already
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  Speaker 1: mastered the art of fire and the building of simple boats.
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  Speaker 1: They brought with them plants and tools and stories. They
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  Speaker 1: also met animals unlike those of the northern continents. Giant
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  Speaker 1: birds once walked there and large marsupials browsed in open woods.
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  Speaker 1: The changing climate and the arrival of people marked the
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  Speaker 1: end of many of those large creatures, but not all
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  Speaker 1: at once and not by a single cause. In the
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  Speaker 1: soft air of evening fires would have glowed next to water,
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  Speaker 1: and someone would have pointed at a star and told
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  Speaker 1: a child where to find it the next night. Return
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  Speaker 1: to the stillness of ice for a moment. Ice can
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  Speaker 1: sound loud when it carves from a cliff into the sea,
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  Speaker 1: but most of the time it is quiet. It is
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  Speaker 1: quiet when it squeezes air into bubbles. It is quiet
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  Speaker 1: when it drags stones over bedrock and scratches long thin
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  Speaker 1: lines that glisten when the sun is at a low angle.
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  Speaker 1: It is quiet when it lays down a floor of
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  Speaker 1: till that feels underfoot like a beach mixed with clay.
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  Speaker 1: As the ice moves, It sometimes shaped rocks into forms
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  Speaker 1: that look like whales at rest, with smooth upstream sides
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  Speaker 1: and plucked downstream sides. When it passed over resistant knots
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  Speaker 1: in the bedrock, it made fluted ridges of sediment that
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  Speaker 1: point in the direction of flow. Those lineations are still
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  Speaker 1: visible on satellite images of the high plains, where a
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  Speaker 1: sensitive eye can see the old motion in the way
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  Speaker 1: the land is combed. Under some ice sheets, water gathered
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  Speaker 1: and pulsed in hidden lakes. From time to time it
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  Speaker 1: drained catastrophically, carving long channels beneath the ice and then
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  Speaker 1: leaving them dry when the ice moved on. Even in
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  Speaker 1: retreat the ice did not simply vanish. It paused and
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  Speaker 1: built low ridges of debris at its margin, then stepped
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  Speaker 1: back and built another. In some valleys those steps make
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  Speaker 1: a necklace of small hills that farmers now plant in curves.
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  Speaker 1: Lift your attention into the air that touched all these places.
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  Speaker 1: Air holds water in the form of vapor, and when
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  Speaker 1: the air is cold, it holds less. In cold times,
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  Speaker 1: clouds were often lower and closer to the ground. Precipitation
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  Speaker 1: fell in different seasons and with different intensity. Dust from
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  Speaker 1: distant deserts could cross oceans and add to the nutrition
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  Speaker 1: of some forests while softening the colour of the sky.
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  Speaker 1: Sea salt blew onto the snow of glaciers and left
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  Speaker 1: a trace in the layers that would later help someone
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  Speaker 1: date a storm. Ash from far eruptions drifted across ice
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  Speaker 1: sheets and settled in layers as thin as a sheet
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  Speaker 1: of paper, making a time marker that would help match
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  Speaker 1: one core to another over a great distance. Tiny organisms
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  Speaker 1: in the ocean responded to changes in light and nutrient
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  Speaker 1: and mixed layer depth by altering the chemistry of their
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  Speaker 1: shells in ways that we can still read. On the land,
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  Speaker 1: trees migrated slowly, sending seeds into valleys and over ridges
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  Speaker 1: as climate lines walked across maps at the speed of
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  Speaker 1: a patient animal. Across Europe, the wind carried fine silt
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  Speaker 1: and laid it down as loess in thick blankets. Those
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  Speaker 1: blankets became soft, pale cliffs along river valleys, where ground
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  Speaker 1: squirrels and humans later carved homes. In China, these layers
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  Speaker 1: are especially thick, and the boundaries between pale loess and
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  Speaker 1: darker soils speak. of the waxing and waning of cold
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  Speaker 1: as clearly as a score tells a musician when to
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  Speaker 1: rise and when to relax. In North America, similar deposits
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  Speaker 1: cover parts of the Midwest and the Great Plains. When
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  Speaker 1: you stand on a gentle hill of Loess and look
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  Speaker 1: toward a river, you are seeing a landscape that remembers
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  Speaker 1: the reach of a glacier and the vigor of meltwater streams.
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  Speaker 1: The animals that lived in this world were not simply
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  Speaker 1: versions of modern creatures dipped in snow. The steppe that
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  Speaker 1: stretched from Western Europe across Siberia to Alaska was a
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  Speaker 1: grassland rich in herbs. It was cold But it was
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  Speaker 1: not sterile. The diet of many large mammals was varied
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  Speaker 1: and nutritious. Mammoths cropped sedges and grasses with careful lips,
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  Speaker 1: and their young followed tracks that were used by many generations.
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  Speaker 1: Woolly rhinos shuffled through snow to reach plants below. Bison
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  Speaker 1: gathered on ridges where the wind kept the snow shallow.
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  Speaker 1: Horses stamped holes to drink from icy streams. This community
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  Speaker 1: of herbivores and the predators that shadowed them created a
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  Speaker 1: moving mosaic of disturbance and renewal that kept the landscape open.
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  Speaker 1: Pollen preserved in lakes shows that these regions were neither
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  Speaker 1: endless woods nor empty rock. They were living meadows under
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  Speaker 1: a wide sky. People lived there too, not just one
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  Speaker 1: kind of people. For a time there were modern humans
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  Speaker 1: and there were other humans with heavy brow ridges and
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  Speaker 1: with strong hands that had been at home in Europe
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  Speaker 1: for hundreds of thousands of years. Far to the east,
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  Speaker 1: another kind of human left traces in caves high in
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  Speaker 1: the mountains. These groups met in some places and exchanged
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  Speaker 1: more than glances. A small portion of the genes in
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  Speaker 1: many people today comes from these meetings. In caves across
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  Speaker 1: southern Europe and across Asia, paintings of animals and signs
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  Speaker 1: and handprints show that stories were told at night when
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  Speaker 1: the wind outside made the entrance sing. People built houses
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  Speaker 1: from bones where wood was scarce. They used needles of
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  Speaker 1: bone to stitch warm clothing from hides and fur. They
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  Speaker 1: made snares and harpoons. They lived on coasts where the
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  Speaker 1: exposed shelf offered shellfish and kelp and small fish that
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  Speaker 1: could be trapped in tidal pools. They followed rivers through
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  Speaker 1: valleys by reading the way driftwood collected and the way
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  Speaker 1: birds moved at dusk. They were not always hungry and
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  Speaker 1: not always fleeing the cold. They were attentive. Move again
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  Speaker 1: toward the sea's edge. With the sea level so much lower,
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  Speaker 1: coral reefs grew at deeper places on the slope. As
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  Speaker 1: the ocean rose at the end of the cold time,
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  Speaker 1: some reefs could keep up with the rise and remained
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  Speaker 1: at the level where light was enough for corals to thrive.
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  Speaker 1: Others drowned and became dark ledges that now host fish
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  Speaker 1: that prefer shade. On some tropical coasts, ancient shorelines now
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  Speaker 1: sit far inland as lines of limestone hills. In the
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  Speaker 1: Caribbean blue holes that were once dry caves filled with
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  Speaker 1: fresh water and then with seawater, they hold layers of
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  Speaker 1: sediment that fell through the water during storms and during
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  Speaker 1: quiet years. Within those layers, there are hints about how
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  Speaker 1: often hurricanes visited and how their tracks shifted with climate.
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  Speaker 1: While the white sheets covered much of the north, not
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  Speaker 1: every place was colder in the same way. The equator
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  Speaker 1: was not an icy desert. The tropics were cooler by
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  Speaker 1: a few degrees and often drier in continental interiors. Rain
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  Speaker 1: belts moved. Some lakes in Africa grew much larger when
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  Speaker 1: monsoon patterns shifted and then shrank again when the belts
• 24:20
  Speaker 1: moved back. Rivers that are small today were once wide
• 24:24
  Speaker 1: highways for fish and hippos. Rock art from a later
• 24:28
  Speaker 1: warm time shows images of animals in places that are
• 24:32
  Speaker 1: now deserts. In South America, the Amazon basin did not
• 24:37
  Speaker 1: turn to dust. Forests contracted in some areas and expanded
• 24:42
  Speaker 1: in others, and river systems reorganized to match the rise
• 24:46
  Speaker 1: and fall of the sea. All through these scenes there
• 24:51
  Speaker 1: is a patient conversation between the solid earth and the
• 24:55
  Speaker 1: moving air and water. When ice grew, the weight pressed
• 24:59
  Speaker 1: the crust down. When ice melted, the land rose. When
• 25:04
  Speaker 1: sea level fell, sediment that would have been trapped on
• 25:07
  Speaker 1: the shelf poured to the outer slope. and into deep basins.
• 25:12
  Speaker 1: When dust blew from cold, dry plains, it fertilized parts
• 25:17
  Speaker 1: of the ocean and invited small plants to grow. When
• 25:21
  Speaker 1: those plants died, some of them sank and carried carbon
• 25:26
  Speaker 1: to the deep. When the ocean took in more carbon,
• 25:29
  Speaker 1: the air grew clearer of it and the cold deepened.
• 25:33
  Speaker 1: While all of that moved through its cycles, volcanoes continued
• 25:38
  Speaker 1: to exhale carbon from the interior, sometimes in quiet, sometimes
• 25:44
  Speaker 1: in short, violent bursts that laid ash across fields of ice.
• 25:50
  Speaker 1: The balance was never exactly the same twice. It was
• 25:54
  Speaker 1: a braided river with many channels. At the end of
• 25:58
  Speaker 1: the last great cold time, the white margins began to
• 26:02
  Speaker 1: pull back. Some pieces broke away as bergs the size
• 26:06
  Speaker 1: of cities and drifted south into the North Atlantic, where
• 26:11
  Speaker 1: they melted and freshened the surface. That freshening in certain
• 26:16
  Speaker 1: events may have slowed the sinking of water that drives
• 26:20
  Speaker 1: part of the ocean conveyor. When that happened, the climate
• 26:25
  Speaker 1: system breathed in and out a little faster for a while,
• 26:30
  Speaker 1: with quick steps of warming and cooling that can be
• 26:33
  Speaker 1: seen in the layers of Greenland ice. In one dramatic interval,
• 26:37
  Speaker 1: a sudden return of cold arrived when warmth seemed certain,
• 26:42
  Speaker 1: a final sharp breath before the peace of the present
• 26:46
  Speaker 1: warm period settled in. The causes of that brief cold
• 26:50
  Speaker 1: have been argued and tested, with suggestions that include a
• 26:55
  Speaker 1: flood of fresh water from a glacial lake and changes
• 26:59
  Speaker 1: in wind and sea ice. Whatever the trigger, the world
• 27:03
  Speaker 1: soon found a new and more gentle balance. As sea
• 27:08
  Speaker 1: level climbed again, the long beaches moved inland, dunes migrated,
• 27:14
  Speaker 1: and estuaries formed where river valleys were drowned. New marshes
• 27:18
  Speaker 1: grew and began to slowly make peat. Fish and birds
• 27:23
  Speaker 1: and people found new routes. Forests filled northern lands. In
• 27:28
  Speaker 1: places where the ground was still rising after the ice
• 27:32
  Speaker 1: let go, the shore marched seaward Even as the global
• 27:36
  Speaker 1: sea rose and old harbours became fields where cattle graze,
• 27:41
  Speaker 1: in other places land subsided as it adjusted to the
• 27:46
  Speaker 1: earlier bulge and the sea advanced more quickly. The map
• 27:50
  Speaker 1: we know today is a snapshot taken on a moving train.
• 27:55
  Speaker 1: It is beautiful and temporary. The glacial world was not
• 28:00
  Speaker 1: one note. It was a long symphony with motifs that
• 28:04
  Speaker 1: returned and changed each time. The instruments were sunlight and orbit,
• 28:09
  Speaker 1: ice and cloud, wind and dust, current and salt, rock
• 28:14
  Speaker 1: and living things. The tempo was slow. The melody was patient.
• 28:20
  Speaker 1: When you walk a beach or climb a hill or
• 28:22
  Speaker 1: drink from a cold spring, You are in a place
• 28:25
  Speaker 1: that has been reworked many times by those quiet forces.
• 28:30
  Speaker 1: A flat farm field in a temperate land may rest
• 28:33
  Speaker 1: on fine sediment that melted from ice and flowed as water.
• 28:38
  Speaker 1: A boulder in a meadow may have been carried on
• 28:40
  Speaker 1: a river of frozen time. A river bend may be
• 28:44
  Speaker 1: held in place by a ridge of old sand laid
• 28:47
  Speaker 1: down when the ice stood still for a season. A
• 28:52
  Speaker 1: calm day in a northern forest with the sound of
• 28:55
  Speaker 1: a bird and a hint of resin and moss is
• 28:58
  Speaker 1: possible because the white left and the green returned. And
• 29:03
  Speaker 1: the white will come again in some far future, long
• 29:08
  Speaker 1: after our brief stories have faded, because the planet continues
• 29:12
  Speaker 1: its long conversation with the sun and with itself. Now
• 29:18
  Speaker 1: let the picture soften. the last light of an ancient
• 29:21
  Speaker 1: day falls across a plain where mammoth hair lifts in
• 29:25
  Speaker 1: a small wind beyond the plain a wide river flows
• 29:30
  Speaker 1: across its own frozen bars far away beyond all maps
• 29:34
  Speaker 1: an ocean carries cold on its back and warmth in
• 29:37
  Speaker 1: its heart high above thin clouds make halos around a
• 29:42
  Speaker 1: pale sun. In the deep cold of Antarctica, a tiny
• 29:46
  Speaker 1: bubble in a blue wall holds the breath of a
• 29:49
  Speaker 1: fern that grew when no one watched. In Greenland, a
• 29:54
  Speaker 1: layer with a little extra dust remembers a century of
• 29:58
  Speaker 1: stronger winds. On a ledge in a cave beside a
• 30:02
  Speaker 1: river that is now far below, a handprint waits in
• 30:06
  Speaker 1: red ochre below an image of a deer. Somewhere, two
• 30:10
  Speaker 1: people step across a dry channel at low tide. They
• 30:15
  Speaker 1: look up at a star that will shift only slightly
• 30:18
  Speaker 1: in their lifetime. The world is quiet and alive, and
• 30:23
  Speaker 1: the long winter is part of its kindness. Across a
• 30:27
  Speaker 1: wide belt that stretched from the Atlantic shores of Western
• 30:31
  Speaker 1: Europe to the cold plains beyond the Bering Strait, the
• 30:34
  Speaker 1: land was neither dense forest nor empty ice. It was
• 30:39
  Speaker 1: a living meadow of cold air and big skies, a
• 30:43
  Speaker 1: mosaic of grasses, sedges, dwarf willows, and cushion plants stitched
• 30:49
  Speaker 1: together by lichens and moss. This was the steppe tundra
• 30:54
  Speaker 1: of mammoths, and it carried herds the way a calm
• 30:57
  Speaker 1: sea carries waves. Mammoths walked there with careful steps, tasting
• 31:02
  Speaker 1: the wind with their trunks, cropping stiff grasses and winter-dried
• 31:07
  Speaker 1: stems with lips that were as precise as fingers. Bison
• 31:12
  Speaker 1: gathered on ridges where wind scoured the snow until it
• 31:16
  Speaker 1: lay only a palm thick. and horses pawed through crusts
• 31:21
  Speaker 1: to find the sweet green crowns that waited beneath. Woolly
• 31:25
  Speaker 1: rhinoceroses moved like low clouds, leaving two curved tracks in
• 31:31
  Speaker 1: shallow drifts. Ground squirrels woke on mild days to tug
• 31:36
  Speaker 1: seeds from their stores. The soils were cold for long months,
• 31:41
  Speaker 1: yet summer brought a burst of light that the plants
• 31:44
  Speaker 1: knew how to use. In that brief season, flowers opened
• 31:49
  Speaker 1: like small lanterns and insects stitched bright threads across the air.
• 31:56
  Speaker 1: The richness of this place came from a curious balance.
• 32:00
  Speaker 1: There was moisture in the form of snow and spring melt,
• 32:04
  Speaker 1: yet trees had trouble taking root in the shallow permafrost
• 32:09
  Speaker 1: and in the restless winds. Without trees, the land stayed open,
• 32:14
  Speaker 1: and without shade, the low sun warmed the ground enough
• 32:18
  Speaker 1: each summer to grow a crowded carpet of leaves close
• 32:22
  Speaker 1: to the soil where warmth lingered. Herds trimmed and stirred
• 32:26
  Speaker 1: this carpet so that fresh growth returned again and again.
• 32:32
  Speaker 1: Predators followed with patience, lions with pale coats haunted riverbanks,
• 32:37
  Speaker 1: hyenas probed abandoned dens for bones, and wolves ran long
• 32:42
  Speaker 1: distances on firm snow. The bones of this community lie
• 32:47
  Speaker 1: today in riverbanks and frozen bluffs. Some still hold threads
• 32:53
  Speaker 1: of hair and the quiet spirals of ancient stomach contents
• 32:57
  Speaker 1: that tell of diets rich in herbs and sedges rather
• 33:01
  Speaker 1: than of coarse woody twigs. The step tundra was not
• 33:05
  Speaker 1: a wasteland. It was a busy table set low to
• 33:08
  Speaker 1: the ground where the ice met rock. The land kept
• 33:13
  Speaker 1: a different diary. Glaciers are slow sculptors, but they are tireless.
• 33:18
  Speaker 1: As ice moved, it dragged grains across bedrock with a
• 33:22
  Speaker 1: pressure that turned crystals into polish. It pressed stones into
• 33:27
  Speaker 1: the rock face until they bit and tore. It plucked
• 33:31
  Speaker 1: at corners and joints and carried the torn blocks within
• 33:35
  Speaker 1: its body as if they were raisins in a very
• 33:38
  Speaker 1: firm cake. Where a glacier paused for a season or
• 33:42
  Speaker 1: for a century, it left a sinuous ridge at its edge,
• 33:46
  Speaker 1: a wall made of everything it had carried. These ridges
• 33:50
  Speaker 1: are moraines, and they come in families. A terminal moraine
• 33:55
  Speaker 1: marks a far reach. Recessional moraines make a chain of
• 33:59
  Speaker 1: low arcs that chart a retreat step by step. Between
• 34:04
  Speaker 1: the ice front and its rivers, the meltwater spread wide
• 34:09
  Speaker 1: as it slowed and dropped its load. Those sheets of
• 34:13
  Speaker 1: braided channels and shifting bars built out wash plains that
• 34:17
  Speaker 1: later dried into ground, as level as a tabletop, with
• 34:22
  Speaker 1: a faint, rippled texture that catches evening shadows. Inside the
• 34:28
  Speaker 1: body of ice itself, Water sometimes gathered and flowed in
• 34:34
  Speaker 1: tunnels along the base. When the glacier melted, these tunnels
• 34:38
  Speaker 1: did not survive, but the sand and gravel that had
• 34:42
  Speaker 1: filled their floors did. The filling remained as long, narrow
• 34:47
  Speaker 1: ridges that run for kilometers with a kind of aim
• 34:51
  Speaker 1: known only to former rivers. These are eskers. And when
• 34:56
  Speaker 1: you walk along one, you are walking the old path
• 34:59
  Speaker 1: of a river that no longer exists, a river that
• 35:03
  Speaker 1: once flowed under a roof of blue. On the high
• 35:07
  Speaker 1: shoulders of mountains, where a small glacier bit into a cirque,
• 35:11
  Speaker 1: the ice scooped bowls as clean as ladles and left
• 35:15
  Speaker 1: behind small lakes that lie still and dark beneath amphitheatres
• 35:21
  Speaker 1: of rock. In lowland plains, the melting of dirty ice
• 35:26
  Speaker 1: left hollows in the outwash that later filled with water
• 35:30
  Speaker 1: and became kettle lakes. Some are perfect circles, some are
• 35:35
  Speaker 1: nests of overlapping ovals, as if a handful of bubbles
• 35:40
  Speaker 1: had rested there and then faded. In a single valley,
• 35:45
  Speaker 1: you can read the grammar of ice in these marks
• 35:48
  Speaker 1: as if you were tracing letters in a calm script.
• 35:53
  Speaker 1: The deepest signatures are cut into the bones of mountain ranges.
• 35:58
  Speaker 1: When glaciers flowed down high valleys, they transformed the cross-section
• 36:03
  Speaker 1: from a sharp V, which is the work of rivers,
• 36:07
  Speaker 1: to a broad profile with a flat floor and steep walls.
• 36:11
  Speaker 1: These valleys, shaped like the letter U, show where ice
• 36:16
  Speaker 1: once shouldered rock aside. Near the headwalls, cirques catch snow
• 36:21
  Speaker 1: that slides in winter, and their lips pour small streams
• 36:25
  Speaker 1: over thresholds in summer. Down the main glen, over-deepening by ice,
• 36:32
  Speaker 1: left long reaches where lakes sit like beads on a string.
• 36:37
  Speaker 1: At the sea, the ice carved channels into drowned valleys
• 36:41
  Speaker 1: and left behind fjords that are calm only on their surfaces.
• 36:46
  Speaker 1: Beneath the surface, their flanks descend great distances, and their
• 36:51
  Speaker 1: floors are sometimes blocked by sills made from debris dropped
• 36:56
  Speaker 1: when the ice margin paused on the way to the sea.
• 37:00
  Speaker 1: In many fjords, walls rise almost sheer from the water.
• 37:05
  Speaker 1: Waterfalls thread down from hanging side valleys that ice did
• 37:09
  Speaker 1: not scour as deeply as the main trough. The air
• 37:13
  Speaker 1: there is salted and still, and the light at certain
• 37:17
  Speaker 1: hours feels as if it has been filtered through quartz.
• 37:22
  Speaker 1: If you look more closely at the places where cold
• 37:26
  Speaker 1: lingers underground, you will see patterns that resemble the skin
• 37:30
  Speaker 1: of a reptile or the tiles of a mosaic. In
• 37:34
  Speaker 1: lands with permafrost, the uppermost ground thaws in summer and
• 37:39
  Speaker 1: refreezes in winter. Water in the soil expands as it freezes,
• 37:45
  Speaker 1: opening and closing pores and moving fine material inch by inch.
• 37:50
  Speaker 1: Over many cycles, the surface organises itself into polygons a
• 37:55
  Speaker 1: few metres across. In the cracks between polygons, ice wedges
• 38:00
  Speaker 1: can grow as meltwater drips in and freezes. The wedges
• 38:05
  Speaker 1: can become as wide as a doorway and taller than
• 38:08
  Speaker 1: a house, buried like crystal roots. When such ice melts,
• 38:13
  Speaker 1: in a warmer time, the ground above can sink to
• 38:16
  Speaker 1: form narrow troughs that wander across a plain. In low
• 38:21
  Speaker 1: mounds called pingos, pressurised groundwater can force a lens of
• 38:26
  Speaker 1: ice to grow and lift the surface like the slow
• 38:30
  Speaker 1: swelling of a drum. When the ice lens melts, the
• 38:33
  Speaker 1: pingo collapses and leaves a ring-shaped hollow that collects snow and, later,
• 38:40
  Speaker 1: quiet water. Hillsides show stripes as stones and finer soils
• 38:45
  Speaker 1: sort themselves into bands under the patient nudging of freeze
• 38:50
  Speaker 1: and thaw. None of this moves fast, and yet a
• 38:54
  Speaker 1: field watched over centuries would look alive. Where the ice
• 38:58
  Speaker 1: was thick enough to dam valleys and basins, melt water
• 39:03
  Speaker 1: pooled into lakes the size of inland seas. One such
• 39:07
  Speaker 1: lake spread across the centre of a continent as the
• 39:11
  Speaker 1: northern ice shield melted back. Its waves knocked cobbles together
• 39:16
  Speaker 1: on shores lined with stranded spruce and willow. and its
• 39:20
  Speaker 1: waters stood high behind ice and moraines that formed temporary dams.
• 39:26
  Speaker 1: When one of those dams failed, the lake sent a pulpit,
• 39:30
  Speaker 1: of water that changed the face of a continent. It
• 39:34
  Speaker 1: carved fresh channels into old rock and left ripples so
• 39:39
  Speaker 1: large that people once mistook them for the ribs of
• 39:43
  Speaker 1: ancient creatures. Another lake west of great mountains filled again
• 39:49
  Speaker 1: and again when an ice lobe blocked a river. Each
• 39:53
  Speaker 1: time the rising water reached a line where the bank
• 39:56
  Speaker 1: gave way, it let loose a flood that ran so
• 40:00
  Speaker 1: fast it carried house-sized boulders as if they weighed no
• 40:04
  Speaker 1: more than oxen. It scoured a scabland of bare rock
• 40:09
  Speaker 1: and cataracts. If you stand there today on a silent
• 40:13
  Speaker 1: evening and run your hands over the basalt, you can
• 40:17
  Speaker 1: feel the smoothness of water that was deeper than most
• 40:20
  Speaker 1: buildings are tall, and that ran with the force of
• 40:24
  Speaker 1: a moving city. After the ice sheets melted, the land
• 40:30
  Speaker 1: did not simply remain where the ice left it. The
• 40:33
  Speaker 1: crust had sagged under the burden. When the weight was removed,
• 40:38
  Speaker 1: the mantle flowed back toward the place from which it
• 40:42
  Speaker 1: had been pushed. The land rose in a slow sigh.
• 40:47
  Speaker 1: Close to the centre of the old ice mass, the
• 40:50
  Speaker 1: rise was greatest. Near the old bulge at the edge,
• 40:54
  Speaker 1: the land sank a little as the centre lifted. Ancient
• 40:58
  Speaker 1: shorelines that once lay at the same height tilted over time.
• 41:03
  Speaker 1: People who built harbours at the margin of a northern
• 41:06
  Speaker 1: sea found that the piers where men tied boats now
• 41:11
  Speaker 1: sit in meadows where cattle graze. Lakes shifted their outlets
• 41:16
  Speaker 1: and carved new channels where water had never flowed before.
• 41:22
  Speaker 1: In some places, the story is recorded on beaches that
• 41:26
  Speaker 1: step up the slope like quiet bleachers. Each bench is
• 41:31
  Speaker 1: a page. You can walk from the newest waves at
• 41:34
  Speaker 1: your feet up through centuries and then millennia to stand
• 41:39
  Speaker 1: where the sea once touched a stone that now smells
• 41:43
  Speaker 1: of resin and leaf litter. While ice was heavy and
• 41:49
  Speaker 1: winds were strong, fine silt travelled far. Dust lifted from
• 41:53
  Speaker 1: bare outwash and from dried lake beds and settled where
• 41:58
  Speaker 1: air slowed and where grasses held it. Loess covered broad
• 42:02
  Speaker 1: swaths of continents with blankets as thick as a cathedral
• 42:06
  Speaker 1: is tall. The texture is soft. and uniform made of
• 42:11
  Speaker 1: tiny crystals and fragments that were broken during freezing and
• 42:16
  Speaker 1: thawing and then sorted by air rain cuts those blankets
• 42:20
  Speaker 1: into steep bluffs where the soil stands nearly vertical yet
• 42:25
  Speaker 1: holds firm in calm weather. In river valleys, pale cliffs
• 42:30
  Speaker 1: of Loess reveal sequences of layers that alternate with ancient soils.
• 42:35
  Speaker 1: The colours shift slowly from cream to light brown to
• 42:40
  Speaker 1: rusty red. Then back again, marking warm intervals when plants
• 42:46
  Speaker 1: held the surface and cold intervals when dust arrived in
• 42:50
  Speaker 1: greater measure. In some regions, these slices of time can
• 42:54
  Speaker 1: be counted and matched to known changes in the orbit
• 42:58
  Speaker 1: of Earth and to the rhythm of ice recorded elsewhere.
• 43:02
  Speaker 1: Farmers later used these deep Loess soils because they are
• 43:07
  Speaker 1: easy to work and rich in minerals. Vines in some
• 43:11
  Speaker 1: lands sink their roots into Loess that remembers ice and
• 43:15
  Speaker 1: wind and give fruit that remembers sun and human patience.
• 43:21
  Speaker 1: The record of that patience is written in many materials
• 43:26
  Speaker 1: that accumulate one layer at a time. In lakes at
• 43:30
  Speaker 1: the foot of glaciers, thin couplets form each year as
• 43:34
  Speaker 1: heavy silt falls in the spring, when rivers run strong
• 43:38
  Speaker 1: with meltwater and fine clay settles in the quiet of
• 43:42
  Speaker 1: winter under ice. These annual layers called varves can be
• 43:47
  Speaker 1: counted like rings in a tree. They often hold sudden
• 43:51
  Speaker 1: dark bands where a landslide or a flood brought an
• 43:55
  Speaker 1: unusual load, and they hold pollen that drifts from nearby hills.
• 44:01
  Speaker 1: In caves where water seeps from roofs and drips from stalactites,
• 44:06
  Speaker 1: the chemistry of each drop carries a small story about
• 44:10
  Speaker 1: the rain that fell above and the vegetation that covered
• 44:14
  Speaker 1: the land. As calcite, is laid down in rings on stalagmites,
• 44:20
  Speaker 1: the oxygen within it records the temperature and seasonal pattern
• 44:25
  Speaker 1: of the past. Ice cores add their bubbles and dust.
• 44:30
  Speaker 1: Marine mud preserves the shells of tiny organisms whose chemistry
• 44:35
  Speaker 1: tells of the warmth and salinity of the sea where
• 44:39
  Speaker 1: they lived. Together, these records tie distant places into a
• 44:45
  Speaker 1: common timeline of long winter and its steps. Within that
• 44:50
  Speaker 1: long winter, there were quick movements that break the idea
• 44:54
  Speaker 1: that ice ages are only slow. Great armadas of icebergs
• 44:59
  Speaker 1: sometimes launched into the North Atlantic when parts of a
• 45:03
  Speaker 1: northern ice sheet became unstable. The bergs carried gravel and
• 45:09
  Speaker 1: sand that fell like a light rain as the ice
• 45:12
  Speaker 1: melted far from land. The layers of coarse grains in
• 45:17
  Speaker 1: deep sea cores record these episodes. They are known by
• 45:21
  Speaker 1: the name of a person who saw their pattern first.
• 45:26
  Speaker 1: Between these sudden iceberg showers, there were intervals when the
• 45:30
  Speaker 1: climate of the north swung from colder to warmer, and
• 45:34
  Speaker 1: back again in a few human lifetimes. These rapid shifts
• 45:40
  Speaker 1: are recorded in the chemistry of Greenland ice as steps
• 45:44
  Speaker 1: in which temperature changed by several degrees within decades. The
• 45:49
  Speaker 1: cause of those swings involved changes in sea ice, winds,
• 45:54
  Speaker 1: and the overturning of water in the oceans. When sea
• 45:58
  Speaker 1: ice retreated, the air above the open water could gain
• 46:02
  Speaker 1: heat and moisture from the sea and the land warmed.
• 46:07
  Speaker 1: When sea ice advanced, the lid returned and the cold deepened.
• 46:12
  Speaker 1: The ocean and the atmosphere danced a fast step within
• 46:17
  Speaker 1: the slow music. At the edge of the last glacial retreat,
• 46:21
  Speaker 1: a final sharp breath of cold descended across the northern hemisphere.
• 46:27
  Speaker 1: This was a brief return of winter strength at a
• 46:30
  Speaker 1: time when warmth had already moved north. and trees were
• 46:34
  Speaker 1: marching into lands that had been tundra. Grasses yielded to shrubs,
• 46:40
  Speaker 1: and then to birch and pine, and then, for a
• 46:44
  Speaker 1: short span, the advance stalled, and in some places reversed.
• 46:49
  Speaker 1: The name for this interval comes from a small alpine
• 46:53
  Speaker 1: flower that appeared in pollen records far south of its
• 46:57
  Speaker 1: current home. The reasons for this pause have been sought
• 47:02
  Speaker 1: in the rooting of meltwater from a shrinking ice shield
• 47:06
  Speaker 1: in sudden pulses that freshened the North Atlantic. and slowed
• 47:11
  Speaker 1: the sinking of dense water, and in the ways winds
• 47:15
  Speaker 1: and sea ice responded to those changes. Whatever the combination
• 47:20
  Speaker 1: of causes, the event ended as quickly as it began,
• 47:24
  Speaker 1: and the world stepped into the mildness of the present
• 47:28
  Speaker 1: warm period, with rivers that ran full of new life
• 47:33
  Speaker 1: and coasts that welcomed forests and salt marshes. In that
• 47:38
  Speaker 1: mildness the traces of Ice Age landscapes did not vanish.
• 47:43
  Speaker 1: The steppe tundra turned in most places to forest and wetland,
• 47:48
  Speaker 1: yet pockets of open grass remained on wind-swept ridges and
• 47:53
  Speaker 1: alpine meadows kept a sample of the old community. Moraines
• 47:58
  Speaker 1: greened with spruce and alder. Eskers became roads and long farms.
• 48:04
  Speaker 1: Kettle lakes grew rings of reeds that whisper in evening breezes.
• 48:09
  Speaker 1: U-shaped valleys filled with orchards that accept the calm air
• 48:14
  Speaker 1: that settles at night on flat floors. Fjords became deep
• 48:19
  Speaker 1: waterways where quiet ferries slide under peaks. Polygon-patterned grounds softened
• 48:25
  Speaker 1: into grass, yet their faint geometry often remains visible from
• 48:30
  Speaker 1: the air, a ghost map of freeze and thaw. The
• 48:34
  Speaker 1: giant lakebeds fed peatlands that store carbon and water, shorelines
• 48:40
  Speaker 1: that had once been even rows in arcs and cupped
• 48:43
  Speaker 1: new harbours where fishing boats rock beside old quays that
• 48:47
  Speaker 1: lie a little higher each generation. Loess soils grew wheat
• 48:54
  Speaker 1: and vines and sunflowers. Varves lay hidden until a worker
• 49:00
  Speaker 1: extracting clay saw the tidy ranks and felt the order
• 49:03
  Speaker 1: that only time can lay down. When you listen to
• 49:07
  Speaker 1: these long stories, the world today feels grounded by more
• 49:12
  Speaker 1: than rock. It feels grounded by memory the next time
• 49:16
  Speaker 1: a north wind clears the sky to a hard blue.
• 49:20
  Speaker 1: imagine the same wind drawing thin cloud lines over a
• 49:24
  Speaker 1: land well beyond the current beaches. Imagine mammoths filing along
• 49:29
  Speaker 1: a ridge toward a shallow crossing on a river that
• 49:33
  Speaker 1: is now a bay. Imagine bergs that once moved silently
• 49:38
  Speaker 1: under a pale sun and left a trail of pebbles
• 49:41
  Speaker 1: over a sea floor that now lies far from ice.
• 49:46
  Speaker 1: Imagine a valley with a round bottom glowing with yellow
• 49:49
  Speaker 1: grasses in the late afternoon and know that ice smoothed
• 49:54
  Speaker 1: that curve. Imagine a hillside where fine dust brought by
• 49:59
  Speaker 1: ancient air feeds a harvest in a year that will
• 50:02
  Speaker 1: never see frost as deep as the old winters. The
• 50:07
  Speaker 1: ice age remains with us in these calm images. Now
• 50:12
  Speaker 1: picture a late summer night. The air is still. In
• 50:15
  Speaker 1: a northern forest, a lake holds the stars on its
• 50:19
  Speaker 1: surface like coins. On the far bank, A rounded boulder
• 50:23
  Speaker 1: sits among blueberry bushes, far from the outcrop where its
• 50:28
  Speaker 1: crystals first cooled. On a levee, a child picks up
• 50:33
  Speaker 1: a stone and sees the shell of a tiny sea
• 50:36
  Speaker 1: creature pressed into it, carried from a place where a
• 50:39
  Speaker 1: glacial lake once spread. On a cliff of pale earth,
• 50:44
  Speaker 1: a swallow slides into a small cave. that was scratched
• 50:48
  Speaker 1: by rain out of dust blown by winds that saw
• 50:51
  Speaker 1: ice at the horizon. In a cave under a limestone ridge,
• 50:56
  Speaker 1: a drop of water falls from a stalactite and leaves
• 51:00
  Speaker 1: a whisper of calcite that records a summer of gentle storms.
• 51:05
  Speaker 1: In a museum, a bubble of air sleeps in a
• 51:08
  Speaker 1: clear cylinder of ice and holds a breath from a
• 51:12
  Speaker 1: world that was cold but alive. The long winter was
• 51:17
  Speaker 1: not an interruption in the story of life. It was
• 51:20
  Speaker 1: a chapter in which the planet learned to hold its
• 51:23
  Speaker 1: breath and then to exhale. Far from the temperate forests
• 51:30
  Speaker 1: and quiet plains, there were moments when the deep earth
• 51:34
  Speaker 1: spoke through the cold air. A volcano does not need
• 51:38
  Speaker 1: a warm world to awaken. During the long winters of
• 51:42
  Speaker 1: the Pleistocene, great eruptions occurred. lifted ash into skies already
• 51:48
  Speaker 1: thin with ice crystals and sea spray. One of the
• 51:52
  Speaker 1: largest known events came from a lake-filled caldera on the
• 51:56
  Speaker 1: island that we now call Sumatra. The eruption spread glassy
• 52:01
  Speaker 1: shards across the Indian Ocean and the Bay of Bengal.
• 52:06
  Speaker 1: A light dusting reached far into South Asia. Layers in
• 52:10
  Speaker 1: both Greenland and Antarctic ice preserve a pulse of acidic
• 52:15
  Speaker 1: fallout from about the same time. For many years, people
• 52:20
  Speaker 1: wondered whether this event turned the world suddenly darker for
• 52:24
  Speaker 1: long spans, and whether life bent under its weight. The
• 52:29
  Speaker 1: record now suggests a quieter story. The cooling was real
• 52:34
  Speaker 1: but brief compared with the long steps of the Ice
• 52:37
  Speaker 1: Age rhythm. Forests did not vanish as a single sea,
• 52:42
  Speaker 1: and people did not shrink to a handful in a
• 52:45
  Speaker 1: single valley. Yet the event left memories in pumice beaches,
• 52:50
  Speaker 1: in altered soils, in the chemistry of ice, and in
• 52:54
  Speaker 1: the teachings of those who watch mountains that breathe. Another
• 53:00
  Speaker 1: giant release came from a restless field near the modern
• 53:04
  Speaker 1: city on the bay. that holds a famous buried city
• 53:09
  Speaker 1: of the Romans. The eruption laid a sheet of glowing
• 53:12
  Speaker 1: ash across the Italian peninsula and sent fine particles over
• 53:18
  Speaker 1: the eastern Mediterranean. In cave floors and in lake beds,
• 53:22
  Speaker 1: a bright layer marks the day the sky turned to glass.
• 53:27
  Speaker 1: The timing sits near the border between two human stories
• 53:31
  Speaker 1: in Europe, a coincidence that invites care. Volcanoes do not
• 53:36
  Speaker 1: act as authors of a single page. They are part
• 53:40
  Speaker 1: of a chorus that includes climate and competition and chance.
• 53:45
  Speaker 1: Far away at the edge of the world that we
• 53:48
  Speaker 1: now call New Zealand, a huge eruption from a caldera
• 53:52
  Speaker 1: that is quiet in our time left ignimbrites that step
• 53:57
  Speaker 1: like frozen waves across a plateau. Ash from that eruption
• 54:02
  Speaker 1: settled into the southern ocean and into the hills of
• 54:06
  Speaker 1: islands where winds still carry a trace of cold. These
• 54:10
  Speaker 1: outbursts did not break the slow breath of the Ice Age.
• 54:14
  Speaker 1: They painted brief shadows onto a canvas already cool and bright.
• 54:19
  Speaker 1: Ash on snow can be an artist as well. A
• 54:22
  Speaker 1: thin coat of dark grains on ice lowers the surface
• 54:26
  Speaker 1: reflectivity and lets sunlight warm the crystal skin. After a
• 54:30
  Speaker 1: fall of ash, meltwater may carve small wells that look
• 54:34
  Speaker 1: like holes made by stars fallen to Earth. These are
• 54:39
  Speaker 1: cryokinite hollows. Within them, microbes build dark granules that collect
• 54:45
  Speaker 1: heat and protect themselves with sheets of ice that act
• 54:49
  Speaker 1: like roofs of glass. In this way, a layer that
• 54:52
  Speaker 1: began as a volcanic cloud becomes a nursery for life
• 54:57
  Speaker 1: on ice. When winter returns, the holes freeze shut and
• 55:02
  Speaker 1: the small community sleeps until the next soft season. As
• 55:07
  Speaker 1: the cold persisted through centuries, belts of rain and belts
• 55:12
  Speaker 1: of dry air drifted. Forest and desert traded places in
• 55:16
  Speaker 1: many regions. The Hadley cells that lift warm air near
• 55:21
  Speaker 1: the equator and bring it down again in subtropics shifted
• 55:26
  Speaker 1: their edges. The summer tracks of storms move. In some years,
• 55:31
  Speaker 1: clouds gathered over savannas that are dry today and filled
• 55:35
  Speaker 1: seasonal lakes in great basins. In other years, forests shrank
• 55:40
  Speaker 1: back to clusters on mountains where clouds still brushed the
• 55:45
  Speaker 1: slopes each morning. Where rain slackened, dunes stitched themselves across
• 55:51
  Speaker 1: plains that had seen trees in warmer times. Where rain returned...
• 55:56
  Speaker 1: Sands held thin woodland and groves of acacia that reached
• 56:01
  Speaker 1: for light. Along coasts, the fall in sea level pushed
• 56:07
  Speaker 1: shorelines away so that mangroves followed the tide into channels
• 56:11
  Speaker 1: that were later drowned again. Forests did not vanish as
• 56:16
  Speaker 1: a single sweep. They retreated to refuges and waited with patience.
• 56:23
  Speaker 1: When warmth returned, they spread back along rivers and ridges
• 56:28
  Speaker 1: like green ink finding old lines. Africa carried many of
• 56:34
  Speaker 1: these movements at once. In some periods, large lakes rose
• 56:39
  Speaker 1: in the eastern rift. They reached levels high enough to
• 56:43
  Speaker 1: join basins that are separate today. Hippos and fish crossed
• 56:48
  Speaker 1: from one watershed to another and left their bones in
• 56:51
  Speaker 1: places that are now dry. Shorelines on hillsides show benches
• 56:57
  Speaker 1: where waves once chewed rock and laid beaches of shell
• 57:01
  Speaker 1: and sand. Farther north the Sahara breathed. In cooler, dry
• 57:06
  Speaker 1: periods it expanded. In certain cool but moist intervals, the
• 57:11
  Speaker 1: winds and the rains came from different directions, and green
• 57:16
  Speaker 1: corridors ran across regions that are now a field of dunes.
• 57:21
  Speaker 1: Rock art carved and painted much later tells of people
• 57:24
  Speaker 1: standing near giraffes and crocodiles in places that now hold
• 57:30
  Speaker 1: only sand and thorn. In southern Africa, small groups used
• 57:35
  Speaker 1: caves and cliffs as shelters through seasons that were colder
• 57:40
  Speaker 1: than now. They made hearths where fish bones and charred
• 57:44
  Speaker 1: seeds still whisper of suppers. On some coasts, they followed
• 57:49
  Speaker 1: the tide and harvested shellfish on rocky benches that were
• 57:54
  Speaker 1: farther from the present line of surf because the sea
• 57:58
  Speaker 1: lay low. In Amazonia, the forest did not disappear during
• 58:02
  Speaker 1: the cold. It became a patchwork. Some areas turned to
• 58:07
  Speaker 1: more open woodland. Others remained wet and closed under a
• 58:11
  Speaker 1: high canopy. Rivers wandered across the lowlands, along paths guided
• 58:17
  Speaker 1: by the fall in sea level and the tilt of
• 58:20
  Speaker 1: small basins. Where the river we now call Amazon meets
• 58:25
  Speaker 1: the sea, the mouth once lay much farther out. The
• 58:29
  Speaker 1: spreading of the delta built islands on what had been land.
• 58:34
  Speaker 1: In the interior, regions that are seasonally flooded today were
• 58:39
  Speaker 1: wider and different when the base level of the main
• 58:42
  Speaker 1: trunk changed. The idea of forest refugees comes from the
• 58:46
  Speaker 1: pattern of species that live today. Some plants and animals
• 58:51
  Speaker 1: cluster in separated zones that make sense if the forest
• 58:56
  Speaker 1: once shrank and then expanded again, leaving pockets of old
• 59:01
  Speaker 1: diversity where it survived the drought. Other places show signs
• 59:05
  Speaker 1: that river levels rose and fell enough to strand fish
• 59:10
  Speaker 1: in low ponds and to send birds to new breeding grounds.
• 59:15
  Speaker 1: When warmth and rain returned in greater measure, vines climbed
• 59:19
  Speaker 1: again to the canopy and the forest spread along the
• 59:23
  Speaker 1: wet corridors until it covered most of the basin as
• 59:27
  Speaker 1: it does now. Europe felt the wind and the quiet
• 59:32
  Speaker 1: of long winters and found comfort in three southern shelters.
• 59:37
  Speaker 1: Iberia kept valleys where laurel and oak grew through the cold.
• 59:42
  Speaker 1: Italy held peninsulas and islands that were protected by seas
• 59:48
  Speaker 1: that drew back but still kept mild air. The Balkans
• 59:53
  Speaker 1: offered mountains and coastal plains that remembered the warmth of
• 59:57
  Speaker 1: ancient seas. From these refugees, many trees later moved north
• 1:00:02
  Speaker 1: as the ice withdrew. The modern pattern of beech and
• 1:00:05
  Speaker 1: oak and pine carries the memory of those migrations. In
• 1:00:10
  Speaker 1: the heart of the continent, steppe tundra reached into what
• 1:00:14
  Speaker 1: are now Germany, Poland and Ukraine. The wind built Loess
• 1:00:20
  Speaker 1: from river floodplains and spread it as a quilt In
• 1:00:24
  Speaker 1: this quilt people hunted reindeer along paths that led between
• 1:00:28
  Speaker 1: white dunes and low rivers that were stiff with ice
• 1:00:32
  Speaker 1: in winter and full of fish in spring. Caves in
• 1:00:36
  Speaker 1: limestone hills held small fires and music made with bone flutes.
• 1:00:42
  Speaker 1: In summer the same hills rang with insect song and
• 1:00:47
  Speaker 1: the air held the sense of time and sage from
• 1:00:51
  Speaker 1: open slopes. Across Asia the story grew larger. Siberia was
• 1:00:57
  Speaker 1: a wide stage for the mammoth steppe. The ground stayed
• 1:01:00
  Speaker 1: frozen at depth, and the topmost layer thawed for only
• 1:01:04
  Speaker 1: a short season. Yet the sun of long summer days
• 1:01:09
  Speaker 1: filled the meadows with plants that are rare today, except
• 1:01:12
  Speaker 1: in mountain valleys where cold still rules. Farther south, the
• 1:01:17
  Speaker 1: vast Loess Plateau in northern China thickened under a strengthened
• 1:01:22
  Speaker 1: winter monsoon that swept dust from the desert. Layers of
• 1:01:26
  Speaker 1: silt alternated with ancient soils that formed during calmer, warmer
• 1:01:32
  Speaker 1: intervals when the summer monsoon reached farther inland. These alternations
• 1:01:38
  Speaker 1: now make a quiet barcode that lines the faces of
• 1:01:42
  Speaker 1: river valleys. In East and South Asia, The monsoon did
• 1:01:47
  Speaker 1: not vanish during cold times, but its timing and reach changed.
• 1:01:52
  Speaker 1: In some intervals, the summer rains weakened and retreated toward
• 1:01:56
  Speaker 1: the ocean. In others, they returned and filled lakes that
• 1:02:01
  Speaker 1: had been dust bowls. In the lands east of the Himalaya,
• 1:02:06
  Speaker 1: the great rivers carried mixed signals. Their headwaters lay near
• 1:02:11
  Speaker 1: the glaciers of the highest peaks. which flowed and thinned
• 1:02:16
  Speaker 1: with the broad climate, while their middle reaches wandered across
• 1:02:20
  Speaker 1: plains that were sometimes dry and sometimes marshy. The ice
• 1:02:25
  Speaker 1: age there was a quilt of water and wind, North
• 1:02:29
  Speaker 1: America wore two caps of ice for long spans. One
• 1:02:34
  Speaker 1: cap rested over the west, its edge climbing into the
• 1:02:38
  Speaker 1: coastal ranges and the crest of the great mountains. The
• 1:02:42
  Speaker 1: other spread across the centre and east over the shield
• 1:02:46
  Speaker 1: of ancient rock and the lowland south of the inland
• 1:02:50
  Speaker 1: sea that once split the continent in two in a
• 1:02:54
  Speaker 1: much older age. Between these caps there were times when
• 1:02:59
  Speaker 1: an interior corridor opened, a plain of sedge and willow
• 1:03:03
  Speaker 1: dotted with shallow lakes and slow rivers clotted with ice
• 1:03:08
  Speaker 1: in winter. Along the Pacific a different path ran. When
• 1:03:13
  Speaker 1: summer came to the edge of the ice, kelp beds
• 1:03:17
  Speaker 1: thrived in the cold, clear water. Shellfish and seaweed and
• 1:03:21
  Speaker 1: fish made a writ pantry. Boats stayed within sight of land,
• 1:03:27
  Speaker 1: and people read the coastline where the sea had stepped
• 1:03:30
  Speaker 1: down and exposed benches and headlands hard as bone. Some
• 1:03:35
  Speaker 1: groups may have followed this line long before the interior
• 1:03:40
  Speaker 1: path opened. They left little on the surface because any
• 1:03:44
  Speaker 1: campsite lay far out on a shelf that is now
• 1:03:47
  Speaker 1: under water. Yet in some coves, away from the waves,
• 1:03:52
  Speaker 1: traces of fires and bones and points found in old
• 1:03:56
  Speaker 1: sediments hint at journeys along this quiet road of the sea.
• 1:04:01
  Speaker 1: To the south, at the end of the great range
• 1:04:04
  Speaker 1: that runs down the spine of a continent, Mountain ice
• 1:04:08
  Speaker 1: gathered and sent fingers into valleys that are long and deep,
• 1:04:13
  Speaker 1: the old ice sheet of Patagonia once filled fjords that
• 1:04:17
  Speaker 1: now hold cold blue water. The wind that runs along
• 1:04:23
  Speaker 1: those coasts today carries the memory of that sheet. East
• 1:04:27
  Speaker 1: of the mountains, broad plains called Pampas were grasslands of
• 1:04:31
  Speaker 1: cool air, while farther north and west dry lands held
• 1:04:35
  Speaker 1: shrubs that can live on little rain. In the high
• 1:04:40
  Speaker 1: Andes above the treeline, small glaciers carved hollows that still
• 1:04:45
  Speaker 1: shine with lakes when the sun is low. Farther north again,
• 1:04:50
  Speaker 1: deserts expanded in rain shadows and left white salt flats
• 1:04:55
  Speaker 1: where lakes had stood. as mirrors in earlier intervals. The
• 1:05:00
  Speaker 1: variety of South America during the cold was remarkable, with
• 1:05:06
  Speaker 1: tropical forests altered but present in the north, high mountain
• 1:05:10
  Speaker 1: cold in the centre, and a broad ice sheet in
• 1:05:14
  Speaker 1: the far south. The meeting of cold and wind and
• 1:05:19
  Speaker 1: sea along the southern coasts then was as grand as
• 1:05:23
  Speaker 1: it is now, but expanded and sharpened by the presence
• 1:05:28
  Speaker 1: of ice. Where tropical seas fell away from their modern shores,
• 1:05:34
  Speaker 1: something unexpected happened. Reefs that had grown in shallow water
• 1:05:39
  Speaker 1: found themselves lifted into air. The living corals at the
• 1:05:43
  Speaker 1: top died, and waves carved notches and platforms into the
• 1:05:48
  Speaker 1: newly exposed limestone. In some places those fossil reefs now
• 1:05:54
  Speaker 1: lie like long low walls far inland, cut into by
• 1:05:58
  Speaker 1: rivers that formed when the sea returned, caves that had
• 1:06:02
  Speaker 1: been dry when the sea was low, flooded with clear
• 1:06:06
  Speaker 1: water that people now explore with lights, following tunnels with
• 1:06:11
  Speaker 1: stalactites that grew in air long ago. On the broad
• 1:06:16
  Speaker 1: shelf of a famous reef off a continent to the south,
• 1:06:20
  Speaker 1: The shoreline was once a hundred kilometre seaward of its
• 1:06:24
  Speaker 1: modern line. Rivers cut canyons into the shelf edge. When
• 1:06:29
  Speaker 1: the sea rose again and warmth returned, corals colonised the
• 1:06:34
  Speaker 1: top of the old reef and began to climb back
• 1:06:38
  Speaker 1: toward the light. Layers within the skeletons of coral heads
• 1:06:42
  Speaker 1: preserve annual bands like the rings of a tree. and
• 1:06:47
  Speaker 1: carry the chemistry of seasons that followed the vanishing of
• 1:06:51
  Speaker 1: the ice domes. The cliffs at the back of tropical
• 1:06:54
  Speaker 1: islands have notches at different heights that mark pauses in
• 1:06:59
  Speaker 1: sea-level rise as the great meltwater pulses slowed and then renewed.
• 1:07:07
  Speaker 1: The land holds the sea's handwriting in shadowed lines that
• 1:07:12
  Speaker 1: crabs and ferns share. creatures of the cold world were
• 1:07:17
  Speaker 1: varied and often large. The famous giants of the north
• 1:07:21
  Speaker 1: were not alone. In Europe, the steppe bison was common
• 1:07:25
  Speaker 1: and quick. In Asia, the saiga moved like wind with
• 1:07:29
  Speaker 1: a nose designed to warm and filter air that came
• 1:07:33
  Speaker 1: cold off snow. In North America, There were camels and
• 1:07:38
  Speaker 1: horses that later vanished from the continent and returned only
• 1:07:42
  Speaker 1: with human travellers much later. There were ground sloths in
• 1:07:47
  Speaker 1: the south forests and savannas, some as big as small
• 1:07:52
  Speaker 1: elephants that pulled branches into mouths like gentle cranes. Armoured
• 1:07:58
  Speaker 1: glyptodonts rolled through dry lands with shells that were heavy
• 1:08:03
  Speaker 1: as doors. On both continents there were predators that match
• 1:08:07
  Speaker 1: our imagination. A cat with long upper canines watched edges
• 1:08:12
  Speaker 1: of forests. Lions larger than modern lions paced the open
• 1:08:17
  Speaker 1: ground of the north. A bear with long legs and
• 1:08:21
  Speaker 1: a short face hunted over long distances and would have
• 1:08:24
  Speaker 1: been a shadow to fear. The end of the cold
• 1:08:29
  Speaker 1: brought a thinning of this parade. The reasons were many
• 1:08:33
  Speaker 1: and are still debated with care. Climate changed quickly and
• 1:08:38
  Speaker 1: some habitats shrank. People found new ways to hunt and
• 1:08:43
  Speaker 1: to travel. Fire changed the makeup of some plant communities.
• 1:08:47
  Speaker 1: The pattern of disappearance varied by region and by species.
• 1:08:51
  Speaker 1: In some places, large animals lasted much longer than in others.
• 1:08:55
  Speaker 1: The quiet truth is that endings in nature are mosaic.
• 1:09:00
  Speaker 1: the Ice Age closed with many small farewells rather than
• 1:09:05
  Speaker 1: a single curtain. If you stand in a museum and
• 1:09:09
  Speaker 1: look into the eyes of a mammoth preserved in ice,
• 1:09:13
  Speaker 1: you see hair that remembers wind. and light. If you
• 1:09:17
  Speaker 1: sit on a coral cliff in a tropical island at
• 1:09:20
  Speaker 1: dusk and look seaward, you see flights of birds over
• 1:09:25
  Speaker 1: a sea that has been lower and higher many times.
• 1:09:29
  Speaker 1: If you walk a line of pale Loess bluffs and
• 1:09:32
  Speaker 1: watch a hawk float on a winter current, you stand
• 1:09:36
  Speaker 1: on dust that came from a far glacier and settled
• 1:09:40
  Speaker 1: in a world that knew no ploughs. If you follow
• 1:09:44
  Speaker 1: an esker through a forest and let your hand drag
• 1:09:48
  Speaker 1: along the gravel, you are tracing the floor of a
• 1:09:51
  Speaker 1: vanished river that ran beneath a roof of ice while
• 1:09:55
  Speaker 1: the sun was small. The Ice Age was not a
• 1:09:59
  Speaker 1: single clean sheet of frost over a silent planet. It
• 1:10:03
  Speaker 1: was a thousand stories that played out together. It was
• 1:10:07
  Speaker 1: volcanoes that whispered through ash on snow. It was forests
• 1:10:12
  Speaker 1: that hid and then returned. It was lakes that grew
• 1:10:16
  Speaker 1: enormous behind walls of ice and then burst in hours.
• 1:10:20
  Speaker 1: It was deserts that walked and then slept. It was
• 1:10:25
  Speaker 1: animals that learned paths across wide meadows and people who
• 1:10:29
  Speaker 1: learned to sew and to sing in caves. It was
• 1:10:33
  Speaker 1: the patient rearrangement of rivers and the careful lifting of
• 1:10:38
  Speaker 1: land as the weight left. In this quiet light, a
• 1:10:42
  Speaker 1: reader of the world can still see those pages. A
• 1:10:46
  Speaker 1: ridge of sand that curves through a pasture is a
• 1:10:49
  Speaker 1: mark of a melting front. A round pond in a
• 1:10:53
  Speaker 1: flat field is the footprint of a lump of buried
• 1:10:56
  Speaker 1: ice that died in place. A row of cobbles on
• 1:11:01
  Speaker 1: a hillside that faces the sea once felt waves at
• 1:11:05
  Speaker 1: a different height. A valley with a letter shape rather
• 1:11:09
  Speaker 1: than a V remembers a visitor who carried stone like cargo.
• 1:11:13
  Speaker 1: A forest that leans north with species that travelled from
• 1:11:18
  Speaker 1: three southern corners of a continent remembers shelters that kept
• 1:11:23
  Speaker 1: warmth alive. A small fossil coral found inland on a
• 1:11:27
  Speaker 1: limestone hill remembers a time when the sea stood in
• 1:11:31
  Speaker 1: that field and saw only stars in the nights of
• 1:11:36
  Speaker 1: a cooler earth. Across the snowy plains of the north
• 1:11:40
  Speaker 1: the nights were long and the horizons wide, and the
• 1:11:44
  Speaker 1: animals that moved there were shaped by space and silence.
• 1:11:49
  Speaker 1: Predators kept their lessons in muscle and bone. In the
• 1:11:53
  Speaker 1: open steppe A lion, larger than the modern African cat,
• 1:11:58
  Speaker 1: hunted without a mane. At least, that is how ancient
• 1:12:01
  Speaker 1: painters in deep caves chose to show him. The lack
• 1:12:05
  Speaker 1: of a mane may have been real, a trim suited
• 1:12:08
  Speaker 1: to cold air and long pursuit. These lions lived not
• 1:12:13
  Speaker 1: only in caves but also on the same windy plateaus
• 1:12:17
  Speaker 1: as mammoths and horses. The caves held their bones because
• 1:12:21
  Speaker 1: caves hold many bones. At some dens on limestone hills,
• 1:12:27
  Speaker 1: hyenas dragged in the legs of bison and the skulls
• 1:12:30
  Speaker 1: of horses and left them piled in hollows. The hyenas
• 1:12:35
  Speaker 1: had jaws that could crack shin bones to lick the
• 1:12:39
  Speaker 1: rich marrow inside. Their dens were family places with many
• 1:12:44
  Speaker 1: generations of tooth marks on the same old stones. They
• 1:12:49
  Speaker 1: laughed and chattered near entrances, glimmering with frost. farther west
• 1:12:54
  Speaker 1: and also across the great plains of the new world
• 1:12:58
  Speaker 1: lived cats whose fangs curved like small moons the sabre
• 1:13:03
  Speaker 1: toothed cats were varied some were heavy and built for
• 1:13:07
  Speaker 1: wrestling in short grass others were long-legged and light Better
• 1:13:13
  Speaker 1: suited for chasing in open land, the scimitar cat of
• 1:13:17
  Speaker 1: Eurasia carried shorter blades and a sleek frame and seems
• 1:13:22
  Speaker 1: to have hunted in daylight over long reaches. The famous
• 1:13:26
  Speaker 1: cat of the Americas was stronger in front than in back,
• 1:13:30
  Speaker 1: with forelimbs built to hold a struggling animal still while
• 1:13:35
  Speaker 1: the long canines made a precise bite in places where
• 1:13:39
  Speaker 1: the flesh is thin. These cats did not always bring
• 1:13:43
  Speaker 1: down giants. Sometimes they ate the same deer and horses
• 1:13:48
  Speaker 1: that wolves and lions pursued. Their style was different. Power
• 1:13:54
  Speaker 1: in a short burst, a hold in the right place,
• 1:13:57
  Speaker 1: a slash to a soft area. Their world was not
• 1:14:01
  Speaker 1: a war of monsters, but a series of careful decisions
• 1:14:05
  Speaker 1: made by animals that had to eat and also had
• 1:14:09
  Speaker 1: to avoid injury. in a cold land where a broken
• 1:14:13
  Speaker 1: limb could mean a long sleep in snow. People shared
• 1:14:18
  Speaker 1: these open lands. They were not one people. Several kinds
• 1:14:23
  Speaker 1: of humans lived near one another in different times and
• 1:14:27
  Speaker 1: sometimes in the same season. In the west of Eurasia
• 1:14:31
  Speaker 1: there were people with long low skulls and strong hands.
• 1:14:36
  Speaker 1: who had already learned the craft of stone long before
• 1:14:40
  Speaker 1: modern humans walked those valleys. Their bones show that they
• 1:14:45
  Speaker 1: were powerful and used their bodies with purpose, lifting and
• 1:14:50
  Speaker 1: carrying and moving through scrub and snow to bring meat
• 1:14:53
  Speaker 1: to fire. They cared for their injured and old. In
• 1:14:57
  Speaker 1: a cave high in the mountains of Central Asia, another
• 1:15:01
  Speaker 1: group left traces of their presence not only in the
• 1:15:05
  Speaker 1: shape of their teeth and their finger bones, but also
• 1:15:09
  Speaker 1: in the letters written inside their cells. A splinter of
• 1:15:14
  Speaker 1: bone gave a quiet message that travels now in the
• 1:15:17
  Speaker 1: blood of living people across Asia and on islands farther south,
• 1:15:23
  Speaker 1: a signal that an evening long ago ended with shared breath,
• 1:15:28
  Speaker 1: and a child who carried two stories at once. In
• 1:15:32
  Speaker 1: many places, modern humans arrived with thinner bones and a
• 1:15:37
  Speaker 1: different kind of toolkit and with the gift of complicated
• 1:15:42
  Speaker 1: language that allowed lessons to pass quickly within a small group.
• 1:15:47
  Speaker 1: The old groups did not vanish at once. They left
• 1:15:51
  Speaker 1: echoes in stone and in jeans and in the necks
• 1:15:54
  Speaker 1: of streams where shelter was good and the winter sun
• 1:15:57
  Speaker 1: fell at a kind angle. Survival in cold is a
• 1:16:03
  Speaker 1: matter of air and cloth and skill. People learned to
• 1:16:07
  Speaker 1: wrap the body in layers that trap the heat in
• 1:16:11
  Speaker 1: still air. They learned to separate hide into thin sheets
• 1:16:15
  Speaker 1: and to scrape until the material was soft and could
• 1:16:19
  Speaker 1: bend around an elbow or a heel. They learned to
• 1:16:24
  Speaker 1: twist sinew into thread that swells when damp and closes
• 1:16:28
  Speaker 1: a seam against wind. The gift that changed the comfort
• 1:16:32
  Speaker 1: of winter was a needle with an eye. The first
• 1:16:36
  Speaker 1: needles with eyes appear in sediments that also hold the
• 1:16:40
  Speaker 1: bones of reindeer and mammoth The needles are small and
• 1:16:45
  Speaker 1: strong and show the careful polish that comes only from
• 1:16:49
  Speaker 1: long use in a skilled hand. With a needle, one
• 1:16:53
  Speaker 1: can sew sleeves that fit and hoods that cup the cheek.
• 1:16:58
  Speaker 1: One can stitch boot liners and stuff them with fur
• 1:17:02
  Speaker 1: facing inward and grass that resists rot and then cover
• 1:17:06
  Speaker 1: the hole with a skin that sheds water. People made
• 1:17:10
  Speaker 1: glue by dry distillation of birch bark and used it
• 1:17:14
  Speaker 1: to join stone to wood and bone to antler. They
• 1:17:19
  Speaker 1: made warm lamps from bowls of stone or bone and
• 1:17:22
  Speaker 1: burned fat with a wick of twisted moss. They carried
• 1:17:26
  Speaker 1: embers under a shell of fungus that smoulders for hours.
• 1:17:31
  Speaker 1: These are simple acts that make a life in a
• 1:17:34
  Speaker 1: hard place feel like a home. Where wood was scarce
• 1:17:39
  Speaker 1: and snow buried branches to the tops of shrubs, people
• 1:17:43
  Speaker 1: built houses with the bones of giants. On river terraces
• 1:17:47
  Speaker 1: in the wide plains of the east, they set jaws
• 1:17:51
  Speaker 1: and tusks in circles and leaned ribs inward to meet
• 1:17:55
  Speaker 1: like hands. Hides stretched over this frame made a skin
• 1:18:00
  Speaker 1: against the wind. Flat shoulder blades laid as shingles along
• 1:18:04
  Speaker 1: the base helped hold the walls against gusts. Inside, the
• 1:18:09
  Speaker 1: floor was cleaned and covered with mats. Hearths took simple forms.
• 1:18:15
  Speaker 1: Some were rings of stone, others were shallow basins lined
• 1:18:20
  Speaker 1: with bone ash that helped the fire rest low and even.
• 1:18:24
  Speaker 1: Wind at ground level is different from the wind in
• 1:18:27
  Speaker 1: the open air. The walls broke it. Snow drifted outside
• 1:18:33
  Speaker 1: and rose against the hide to make a white berm
• 1:18:37
  Speaker 1: that sealed the base. The smoke from slow fires found
• 1:18:41
  Speaker 1: its way through seams and left a deep smell in
• 1:18:44
  Speaker 1: the fabric. Pieces of fat hung near the warmth. The
• 1:18:48
  Speaker 1: sounds inside were small, a whisper of someone scraping a hide,
• 1:18:54
  Speaker 1: the high note of a cord pulled through an eye,
• 1:18:57
  Speaker 1: a child learning how to pluck sinew strands into threads
• 1:19:01
  Speaker 1: that will not break. In this same world, art found
• 1:19:05
  Speaker 1: refuge under stone. The paintings in deep caves do not
• 1:19:10
  Speaker 1: feel hurried. They are the work of hands that had
• 1:19:13
  Speaker 1: time and a reason beyond hunger. Some animals are drawn
• 1:19:18
  Speaker 1: with a care for the curve of a neck that
• 1:19:21
  Speaker 1: suggests the artist knew these bodies as closely as a
• 1:19:25
  Speaker 1: shepherd knows sheep. The colours are made from crushed ochre
• 1:19:31
  Speaker 1: and charcoal and sometimes from manganese minerals that give a
• 1:19:35
  Speaker 1: soft black. Fingers help to blend edges. Torches lit the
• 1:19:41
  Speaker 1: wall with warm light while someone placed the palm of
• 1:19:45
  Speaker 1: a hand against the stone and blew pigment through a
• 1:19:49
  Speaker 1: tube to leave a negative, a kind of signature that
• 1:19:53
  Speaker 1: many people carry. The music of these places is made
• 1:19:57
  Speaker 1: with flutes carved from hollow bird bones or from the
• 1:20:01
  Speaker 1: tusks of young mammoths split and hollowed and then joined
• 1:20:06
  Speaker 1: again with care so that the two halves make a
• 1:20:09
  Speaker 1: smooth tube. When played, a flute carved from a vulture
• 1:20:14
  Speaker 1: bone sings a clean tone that echoes in the chamber
• 1:20:18
  Speaker 1: and makes the hairs rise without fear. At some sites
• 1:20:23
  Speaker 1: there are marks of percussion If you tap certain stalactites,
• 1:20:27
  Speaker 1: they ring like bells at different pitches. People found those
• 1:20:32
  Speaker 1: tones and may have used sound as a map to
• 1:20:36
  Speaker 1: tell where the chambers widen and where the roof is near.
• 1:20:41
  Speaker 1: Lots of journeys during cold times were not made through
• 1:20:45
  Speaker 1: forests or over high passes, but along the margins where
• 1:20:50
  Speaker 1: land and sea speak to each other. With the ocean
• 1:20:54
  Speaker 1: stepped down, long stretches of continental shelf were dry or
• 1:20:59
  Speaker 1: lay in very shallow water. Beaches were wide and firm.
• 1:21:04
  Speaker 1: Dunes wandered quickly after storms and then rested in calm weather.
• 1:21:09
  Speaker 1: The rack line held seaweed, shells, driftwood, and small creatures
• 1:21:14
  Speaker 1: that expire with the tide. A band of life runs
• 1:21:19
  Speaker 1: along such a coast, full of fish and birds and
• 1:21:23
  Speaker 1: seals and mollusks. People who learned to read tides and
• 1:21:27
  Speaker 1: to move with the predictable rhythm of the moon found
• 1:21:31
  Speaker 1: in these places a corridor that needed no trail. One
• 1:21:36
  Speaker 1: can set a small boat on water and follow kelp
• 1:21:39
  Speaker 1: forests that outline the shore. The forests are nurseries for
• 1:21:44
  Speaker 1: many species. They also make the sea calm beneath their leaves.
• 1:21:49
  Speaker 1: A camp under a headland can stay warm with blubber
• 1:21:53
  Speaker 1: or with driftwood, and a small group can walk the
• 1:21:56
  Speaker 1: same line for weeks and find food each day without
• 1:22:00
  Speaker 1: climbing steep slopes into deep snow. Many of the signs
• 1:22:05
  Speaker 1: of such travel are now underwater, but some coves still
• 1:22:09
  Speaker 1: hold lenses of black soil full of shell that speak
• 1:22:14
  Speaker 1: of repeated visits by quiet people who left only the
• 1:22:18
  Speaker 1: bones of their dinners and the small beads they used
• 1:22:22
  Speaker 1: to seal social life. Far from shore, the frozen sea
• 1:22:27
  Speaker 1: itself is a restless country. The first crystals grow like
• 1:22:32
  Speaker 1: stars in supercooled water, and then gather into grease ice
• 1:22:36
  Speaker 1: that looks like a thin sheen of oil. Later, the
• 1:22:40
  Speaker 1: surface rolls with cakes of pancake ice, each piece with
• 1:22:44
  Speaker 1: a raised rim made by collisions in small waves. Where
• 1:22:48
  Speaker 1: the pack opens, a stretch of black water appears called
• 1:22:52
  Speaker 1: a lead, and steam rises from it in cold air.
• 1:22:56
  Speaker 1: These openings are doors for seals and for narwhals, and
• 1:23:01
  Speaker 1: also for people who hunt them from the edge. In
• 1:23:04
  Speaker 1: some places, recurring openings called palinias stay clear of ice
• 1:23:10
  Speaker 1: for much of the winter because of wind or because
• 1:23:13
  Speaker 1: warm water upwells from below. Around them, life is thick.
• 1:23:19
  Speaker 1: In quiet corners, branching stalactites of clear ice called brinicles
• 1:23:24
  Speaker 1: grow downward from the surface when very cold salty water
• 1:23:28
  Speaker 1: drains from the pack and freezes the less salty water nearby.
• 1:23:33
  Speaker 1: They look like glass fingers and move so slowly that
• 1:23:37
  Speaker 1: few eyes have watched them form. When large icebergs drift
• 1:23:42
  Speaker 1: from the edge of a glacier, they carry a deep
• 1:23:45
  Speaker 1: keel that ploughs the sea floor. Later, when the sea
• 1:23:49
  Speaker 1: falls calm, a diver can discover long scars where the
• 1:23:54
  Speaker 1: iceberg passed. Storms in these seas carry shards of ice
• 1:23:59
  Speaker 1: blown far inland so that hilltops glisten like the backs
• 1:24:04
  Speaker 1: of sleeping fish, and the sound a traveller hears is
• 1:24:07
  Speaker 1: a ringing hiss that merges with the wind. The end
• 1:24:11
  Speaker 1: of the long winter did not arrive as a dramatic
• 1:24:15
  Speaker 1: single thaw. It was more like the loosening of a belt.
• 1:24:19
  Speaker 1: The ice shields on continents thinned. In some summers, the
• 1:24:24
  Speaker 1: edges wasted so far that long tongues broke away and
• 1:24:28
  Speaker 1: drifted out into the North Atlantic. As they melted, they
• 1:24:33
  Speaker 1: dropped stones that had been quarried by glaciers from faraway ridges.
• 1:24:38
  Speaker 1: Those stones now dot the floor of the deep ocean
• 1:24:42
  Speaker 1: in layers that align with moments when the ice sheets faltered. Water,
• 1:24:48
  Speaker 1: released by the melting, raised the sea by steps. There
• 1:24:52
  Speaker 1: were intervals when the rise was slow and others when
• 1:24:56
  Speaker 1: it quickened. The fastest rises came during pulses when many
• 1:25:01
  Speaker 1: glaciers retreated at once, or when a large lake held
• 1:25:05
  Speaker 1: back by ice found a path and poured its contents
• 1:25:10
  Speaker 1: into the sea. Meltwater moved in sheets over outwash and
• 1:25:15
  Speaker 1: in deep channels under ice. It liberated caves that had
• 1:25:19
  Speaker 1: been filled with frozen slurry and sent fresh water through cracks,
• 1:25:24
  Speaker 1: where it had not flowed for thousands of years. Forests
• 1:25:29
  Speaker 1: followed the retreat. first with shrubs that can stand cold
• 1:25:34
  Speaker 1: and then with trees that throw deep shade and make
• 1:25:38
  Speaker 1: a calm underworld where moss thrives. Animals that had been
• 1:25:43
  Speaker 1: kept north or south by ice found new roads and
• 1:25:47
  Speaker 1: met others that were moving in the opposite direction. As
• 1:25:51
  Speaker 1: the ice departed, it left behind a raw surface that
• 1:25:55
  Speaker 1: invited water to draw a new map. Many rivers did
• 1:26:00
  Speaker 1: not take the same path as the streams that existed
• 1:26:04
  Speaker 1: before the ice came. They were forced into new channels
• 1:26:08
  Speaker 1: by ridges of debris and by basins that the ice
• 1:26:12
  Speaker 1: had scooped into the bedrock. In some places, two rivers
• 1:26:17
  Speaker 1: met and chose a single outlet where there had been two.
• 1:26:21
  Speaker 1: In the lands of the north, a necklace of large
• 1:26:25
  Speaker 1: lakes formed along the rim of the Shield where the
• 1:26:28
  Speaker 1: ice had pressed the crust down deeply. The water sought
• 1:26:32
  Speaker 1: a route to the sea and changed that route as
• 1:26:36
  Speaker 1: the land rose and the ice drew back. One day
• 1:26:40
  Speaker 1: a lake might drain to the south along a particular line.
• 1:26:45
  Speaker 1: A few centuries later it might find a lower saddle
• 1:26:49
  Speaker 1: and drain to the east in a great rush that
• 1:26:52
  Speaker 1: carved a fresh valley. In Europe, the basin that would
• 1:26:57
  Speaker 1: become the Baltic swung through a series of stages, at
• 1:27:00
  Speaker 1: times receiving a river from the west, at times becoming
• 1:27:05
  Speaker 1: a brackish arm of the ocean, and then a fresh
• 1:27:09
  Speaker 1: lake again as the land rose. In the North Atlantic,
• 1:27:13
  Speaker 1: a broad plain between islands and the mainland was drowned
• 1:27:17
  Speaker 1: step by step as the sea returned. That plain had
• 1:27:21
  Speaker 1: carried herds and people for many thousands of years. When
• 1:27:26
  Speaker 1: the water rose, the communities moved to higher dunes and
• 1:27:30
  Speaker 1: left behind hearthstones and nets, pinned beneath sand and then salt.
• 1:27:35
  Speaker 1: In this new world, warmth brought steadier rains, and the
• 1:27:39
  Speaker 1: sky found a rhythm that was closer to the one
• 1:27:43
  Speaker 1: we know. Trees marched north across continents at walking speed,
• 1:27:48
  Speaker 1: generation by generation. and pine were scout trees. Oak and
• 1:27:54
  Speaker 1: beech followed. Lakes cleared and grew layers of quiet mud
• 1:27:59
  Speaker 1: where pollen fell each season and kept a diary of
• 1:28:03
  Speaker 1: the forest as it changed. Coral reefs climbed toward the
• 1:28:07
  Speaker 1: light and built rings around atolls that had been cliffs
• 1:28:11
  Speaker 1: when the sea was low. The long chain of the
• 1:28:15
  Speaker 1: ocean conveyor flowed in a pattern that brought mild air
• 1:28:20
  Speaker 1: to northern coasts and carried oxygen to the deep. Some
• 1:28:24
  Speaker 1: of the great animals of the cold did not make
• 1:28:27
  Speaker 1: this crossing. The reasons are a soft tangle. Changes in food,
• 1:28:34
  Speaker 1: changes in competition, warmer summers that stressed large bodies, the
• 1:28:39
  Speaker 1: arrival of people with more complex hunting strategies and perhaps
• 1:28:44
  Speaker 1: with new habits of fire, and the loss of gentle
• 1:28:47
  Speaker 1: refugees along the edges all had a hand. The animals
• 1:28:52
  Speaker 1: that did remain found new roots and new homes. Fish
• 1:28:57
  Speaker 1: moved into rivers that had been under ice. Birds learned
• 1:29:01
  Speaker 1: new wetlands. People planted seeds and watched them sprout, and
• 1:29:06
  Speaker 1: learned to harvest where they had once only gathered and pursued.
• 1:29:11
  Speaker 1: The quiet time that followed the last breath of cold
• 1:29:15
  Speaker 1: is sometimes called a new age of the whole. It
• 1:29:19
  Speaker 1: is an age of steady warmth compared with the quick
• 1:29:23
  Speaker 1: changes of the late ice time. It is the span
• 1:29:27
  Speaker 1: in which human communities learned to settle and to weave
• 1:29:31
  Speaker 1: and to mark time by rain. It is also a
• 1:29:35
  Speaker 1: span in which the memory of winter was never lost
• 1:29:39
  Speaker 1: by the land. Moraines became ridges under beach. Eskers became
• 1:29:44
  Speaker 1: long roads that guide travellers today. Fjords became deep gardens
• 1:29:50
  Speaker 1: for kelp and cod. Kettle lakes became sanctuaries for reeds
• 1:29:55
  Speaker 1: and for people who loved the sound of their leaves.
• 1:29:58
  Speaker 1: The scars of iceberg keels became furrows where new corals began.
• 1:30:04
  Speaker 1: The terraces cut by the sea at low stands became
• 1:30:08
  Speaker 1: benches where farmers laid neat stones into walls. Even now,
• 1:30:14
  Speaker 1: somewhere a block of old ice left in thick sediment
• 1:30:17
  Speaker 1: close to a northern coast is melting in silence and
• 1:30:21
  Speaker 1: a small pond is forming where its crown once lay.
• 1:30:25
  Speaker 1: In the evening the pond will mirror a sky that
• 1:30:28
  Speaker 1: glows for a long time because the sun slides at
• 1:30:32
  Speaker 1: a shallow angle in the latitudes where winter used to
• 1:30:36
  Speaker 1: keep a longer hold. This is the shape of that
• 1:30:41
  Speaker 1: long season of earth. It is not only cold. It
• 1:30:44
  Speaker 1: is also invention. It is also art. It is streets
• 1:30:49
  Speaker 1: laid by shorebirds along wet sand where people learned to
• 1:30:53
  Speaker 1: read a tide. It is the trail of an elk
• 1:30:56
  Speaker 1: printed in mud under a spruce where a child learned
• 1:31:01
  Speaker 1: that animals move most easily along contours rather than straight lines.
• 1:31:07
  Speaker 1: It is the careful holes in a needle and the
• 1:31:10
  Speaker 1: angled lamp that does not make soot. It is a
• 1:31:14
  Speaker 1: flute that sings a note that would not be out
• 1:31:17
  Speaker 1: of place in a room of wood and glass today.
• 1:31:21
  Speaker 1: It is a painting of a horse with a swollen
• 1:31:24
  Speaker 1: belly in spring and a foal at her side in summer.
• 1:31:28
  Speaker 1: It is a ridge of stones arranged in a circle
• 1:31:32
  Speaker 1: and a roof made of ribs where stories were told
• 1:31:36
  Speaker 1: while wind walked outside. Now let the room grow quiet again.
• 1:31:42
  Speaker 1: The old ice lies far away, pressed into blue memory
• 1:31:46
  Speaker 1: under new snow. The open land of mammoths is now
• 1:31:50
  Speaker 1: a quilt of fields and towns, with names that carry
• 1:31:54
  Speaker 1: water and wind inside them. The rivers that found their
• 1:31:58
  Speaker 1: way over fresh ground run through cities yet still cut
• 1:32:03
  Speaker 1: toward the sea, with the same patience they learned when
• 1:32:07
  Speaker 1: they were young. the ocean rides higher over banks that
• 1:32:11
  Speaker 1: were once beaches where footsteps dried in sun and then
• 1:32:16
  Speaker 1: were taken by a slow tide. If you listen as
• 1:32:20
  Speaker 1: the night settles, you can hear that the planet is
• 1:32:23
  Speaker 1: still making its soft adjustments. A grain of silt falls
• 1:32:28
  Speaker 1: to a lake bottom. A small wave licks a line
• 1:32:32
  Speaker 1: on stone a little higher than the one it licked
• 1:32:35
  Speaker 1: last night. A bird takes a seed north. The long
• 1:32:40
  Speaker 1: winter is finished for now, but its work remains as
• 1:32:43
  Speaker 1: a gentle frame for all that came after. Thank you
• 1:32:48
  Speaker 1: for travelling through this quiet history. May the steady breath
• 1:32:52
  Speaker 1: of the planet guide your own breath to a calm
• 1:32:56
  Speaker 1: and easy rhythm. Sleep well and let the ancient snowfields
• 1:33:01
  Speaker 1: keep watch as you rest.