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New York City is Sinking! · PlanetGeo: The Geology Podcast

• 0:02
  SPEAKER_01: Welcome to Planet Geo, the podcast where we talk about our amazing planet, how it works, and why it matters to you.
• 0:12
  SPEAKER_00: Hey, how are you doing, Jesse Remink?
• 0:15
  SPEAKER_00: Dr.
• 0:15
  SPEAKER_00: Jesse Remink.
• 0:16
  SPEAKER_00: Yeah, yeah.
• 0:16
  SPEAKER_00: Get it right.
• 0:17
  SPEAKER_00: Get it right.
• 0:18
  SPEAKER_00: I'm doing well.
• 0:19
  SPEAKER_00: How are you?
• 0:20
  SPEAKER_00: I'm great.
• 0:21
  SPEAKER_00: I'm great.
• 0:22
  SPEAKER_00: Hey, do you got your radio voice on, Kermit?
• 0:25
  SPEAKER_00: I'm feeling particularly Kermit-y today.
• 0:28
  SPEAKER_01: I'm getting over a cold.
• 0:29
  SPEAKER_01: So I'm probably like a more extreme version of Kermit right now.
• 0:35
  SPEAKER_01: Super nasally Kermit over here.
• 0:37
  SPEAKER_01: That's the best kind.
• 0:39
  SPEAKER_01: Yeah.
• 0:39
  SPEAKER_01: Well, there we go.
• 0:40
  SPEAKER_01: You got me.
• 0:41
  SPEAKER_01: You got me.
• 0:41
  SPEAKER_01: I'm here, baby.
• 0:42
  SPEAKER_01: Um so, Chris, before we get going today, we had an update that I think everybody will be interested in.
• 0:48
  SPEAKER_01: We got another email from Joyce.
• 0:50
  SPEAKER_01: Did you see?
• 0:51
  SPEAKER_01: We did.
• 0:52
  SPEAKER_01: You always miss the emails from your mom to our to our podcast email.
• 0:57
  SPEAKER_01: So she um she just said that she's enjoying the the good humored, silly banter, and uh she really likes biffs because she likes to pick up the pretty ones.
• 1:06
  SPEAKER_01: So there we go.
• 1:07
  SPEAKER_00: That's true.
• 1:07
  SPEAKER_00: Good.
• 1:08
  SPEAKER_00: I have no idea when my mom emailed me that, like or us, I should say.
• 1:11
  SPEAKER_00: I I just didn't look.
• 1:12
  SPEAKER_00: I had a very busy day yesterday, you know, stump grinding.
• 1:16
  SPEAKER_00: My whole other rest of the day was occupied doing track stuff, and so I I didn't get to it.
• 1:21
  SPEAKER_00: No.
• 1:21
  SPEAKER_01: Yeah, you didn't get to it, so apologize to your mom.
• 1:24
  SPEAKER_01: I'm sorry, mom.
• 1:26
  SPEAKER_01: It's always a nice email.
• 1:27
  SPEAKER_01: It's always nice getting listener emails, and it's particularly nice from Joyce.
• 1:30
  SPEAKER_01: I really enjoy those ones.
• 1:31
  SPEAKER_01: So, Chris, today we're talking about really uh a research publication that that made its way into the science news article space and on to CNN and all sorts of stuff, but it's really about New York City sinking under its own weight.
• 1:45
  SPEAKER_01: And you are the one who pinged this to me.
• 1:47
  SPEAKER_01: Where did you come across it?
• 1:50
  SPEAKER_00: That's a funny story, at least to me it's funny.
• 1:52
  SPEAKER_00: I got a text from my son, and he says, Hey dad, I was listening to this podcast, and they were interviewing these guys from the USGS about New York City sinking.
• 2:03
  SPEAKER_00: And he said, What do you think about that?
• 2:05
  SPEAKER_00: Well, I had a lot of mixed emotions about that.
• 2:08
  SPEAKER_00: One, my heart was warmed instantly that my son was listening to a podcast that involved science.
• 2:15
  SPEAKER_00: I was I was like, Oh, I love that boy.
• 2:18
  SPEAKER_00: But then I sent a text back that did not like depict that emotion.
• 2:23
  SPEAKER_01: You probably didn't compliment him.
• 2:24
  SPEAKER_01: You're probably like, What would you do?
• 2:27
  SPEAKER_00: I said, Hey, you took my geology class, you tell me what you think about that.
• 2:33
  SPEAKER_00: And then he gives me some snarky response back, like me being a nerd or something like that.
• 2:38
  SPEAKER_00: And then I came back with something even, you know, to one up him.
• 2:43
  SPEAKER_00: But that's the where the idea came from, is from my son.
• 2:47
  SPEAKER_00: So yeah.
• 2:48
  SPEAKER_01: Hey, there we go.
• 2:48
  SPEAKER_01: Your son is is paying attention to the geoscience news world.
• 2:51
  SPEAKER_01: That's uh that's amazing.
• 2:52
  SPEAKER_01: Good work.
• 2:53
  SPEAKER_00: It actually is, and he does a good job of keeping up with our podcast, which like he'll ask me questions.
• 2:59
  SPEAKER_00: I was just out there visiting him a couple weeks ago, and and he's like, Hey dad, um, and he brings up these scientific geology things, these questions that he has, and every time it catches me off guard.
• 3:11
  SPEAKER_00: Like uh he should listen to our podcast because he's my boy, but it warms the heart to know that he actually does, which is more than I can say for my daughter.
• 3:20
  SPEAKER_00: You know, she doesn't she doesn't say anything, but her friends listen to the podcast.
• 3:25
  SPEAKER_00: So I'm doing a shout out to Bella's friends for listening to the podcast.
• 3:30
  SPEAKER_00: Keep it going, it's awesome.
• 3:32
  SPEAKER_00: Um, and you you you all need to do a better job of shaming Bella for not listening.
• 3:37
  SPEAKER_00: Yeah, that's right.
• 3:37
  SPEAKER_01: Give her a hard time.
• 3:39
  SPEAKER_01: Okay, so oh man.
• 3:41
  SPEAKER_01: So the title of the news article here, and like I said, this made its way around the world in the geoscience news space, and actually the real news space.
• 3:49
  SPEAKER_01: You know, this was on CNN, this was discussed a lot of different places.
• 3:54
  SPEAKER_01: The one we focused on, or the one we looked at, was a Scientific American article that the title is just New York City is sinking under its own weight.
• 4:00
  SPEAKER_01: And this is really based on a journal article, which we've talked about how to read journal articles recently, Chris.
• 4:06
  SPEAKER_01: So everybody should not be afraid to read a journal article.
• 4:09
  SPEAKER_01: But it's the title of this one is The Weight of New York City: Possible Contributions to Subsidence from Anthropogenic Sources.
• 4:15
  SPEAKER_01: So yeah, we'll we'll talk about the different titles here, I think maybe, but I think those are the two things we're talking about.
• 4:22
  SPEAKER_00: I gotta ask, you just said subsidence.
• 4:25
  SPEAKER_00: I always say subsidence.
• 4:27
  SPEAKER_00: Who's right?
• 4:28
  SPEAKER_01: I think I've uh maybe lost the Midwestern uh framing.
• 4:32
  SPEAKER_01: I also don't say is that what it is?
• 4:34
  SPEAKER_01: Yeah, I also say data instead of data, which a lot of people in Michigan say data.
• 4:39
  SPEAKER_00: Oh, yeah.
• 4:40
  SPEAKER_00: Okay.
• 4:40
  SPEAKER_00: So you think subsidence is a Midwest thing?
• 4:42
  SPEAKER_00: It might be, I'm not sure.
• 4:44
  unknown: Okay.
• 4:44
  SPEAKER_00: I'll have to break the mold and switch it up and say subsidence though.
• 4:47
  SPEAKER_01: You know, I also sometimes say basalt instead of basalt these days, because I've hung around with a lot of English geologists before.
• 4:54
  SPEAKER_00: Oh my gosh.
• 4:55
  SPEAKER_00: Do you also say methane instead of methane?
• 4:58
  SPEAKER_00: No, no, aluminium, aluminum instead of I can never say it the way they anyways.
• 5:04
  SPEAKER_00: All right, let's go.
• 5:05
  SPEAKER_00: Let's jump into this.
• 5:05
  SPEAKER_00: Let's get into some science.
• 5:07
  SPEAKER_01: Yeah.
• 5:07
  SPEAKER_01: So I could Chris, what were your main takeaways after after your son pinged you with this?
• 5:12
  SPEAKER_01: What was your knee-jerk reaction?
• 5:14
  SPEAKER_01: And then what was your deep reaction?
• 5:17
  SPEAKER_00: Okay, yes.
• 5:17
  SPEAKER_00: Good, good question.
• 5:18
  SPEAKER_00: I didn't read the article, I just was responding instantaneously to texts, right?
• 5:23
  SPEAKER_00: And I'm thinking, well, that makes sense.
• 5:25
  SPEAKER_00: I mean, New York City has a lot of massive buildings, it's a staggering amount, actually.
• 5:31
  SPEAKER_01: Yes, it is.
• 5:32
  SPEAKER_01: And let's put some numbers on that real quick, because this is the main contribution that this paper, the research paper, did is they added all of this up.
• 5:40
  SPEAKER_01: And so as of 2020, New York City had 8.8 million people roughly.
• 5:44
  SPEAKER_01: So this is the most populous city in the US.
• 5:46
  SPEAKER_01: It had almost 1.1 million buildings, and they added these up.
• 5:51
  SPEAKER_01: They looked at the commercial use.
• 5:53
  SPEAKER_01: Is it a big office building?
• 5:54
  SPEAKER_01: Is it an industrial building?
• 5:55
  SPEAKER_01: Is it residential?
• 5:56
  SPEAKER_01: And they added all that up and they said the number that is the weight of New York City, the five boroughs, 764 billion B billion kilograms, or 1.68 trillion with a T trillion pounds.
• 6:13
  SPEAKER_01: That's a lot of weight.
• 6:15
  SPEAKER_00: That's a lot of weight.
• 6:16
  SPEAKER_00: So here's where my mind went to.
• 6:18
  SPEAKER_00: I didn't know the numbers, I just knew New York is big, it's got a lot of weight on it from these buildings.
• 6:24
  SPEAKER_00: And I thought, all right, well, that's a geological principle.
• 6:27
  SPEAKER_00: It's called isostasy.
• 6:28
  SPEAKER_00: And so this is a really good opportunity for us to review that, right?
• 6:32
  SPEAKER_01: Define that, define that.
• 6:33
  SPEAKER_01: Because I don't know if we've actually really hammered isostasy before in the podcast.
• 6:38
  SPEAKER_01: So will you just define it real quick, Chris?
• 6:40
  SPEAKER_00: I'll do my best.
• 6:41
  SPEAKER_00: You're putting me on the spot.
• 6:42
  SPEAKER_00: But isostasy is basically this gravitational balance.
• 6:46
  SPEAKER_00: Um, let me explain it this way.
• 6:48
  SPEAKER_00: If you have two people walking on a beach, on the part of the beach that it is kind of like somewhat wet and somewhat it's not like soupy, runny or anything like that.
• 6:59
  SPEAKER_00: They're gonna leave footprints in the sand.
• 7:01
  SPEAKER_00: You have one person that's six foot eight and weighs three hundred and fifty pounds, and they're walking on the beach, and they're walking next to somebody that's five foot tall and weighs a hundred pounds.
• 7:12
  SPEAKER_00: The bigger person is gonna have deeper footprints than the smaller person, right?
• 7:15
  SPEAKER_00: It's a gravitational balance.
• 7:17
  SPEAKER_00: And so geologically, we have a lot of things that can do this, uh, you know, have this gravitational effect on the surface of the earth.
• 7:25
  SPEAKER_00: For instance, glaciers at the height of the last ice age.
• 7:28
  SPEAKER_00: You had glaciers that were, you know, maybe three miles thick, right?
• 7:32
  SPEAKER_00: I mean, that's a lot of weight.
• 7:34
  SPEAKER_00: And that caused then that thickest part of the glacier to cause the ground below it to sink the most.
• 7:41
  SPEAKER_00: It's like deep footprints, right?
• 7:43
  SPEAKER_00: A lot of weight, a lot of sinking.
• 7:45
  SPEAKER_00: Mountains do the same thing.
• 7:47
  SPEAKER_00: The taller the mountains are, the deeper their roots extend down into the mantle.
• 7:53
  SPEAKER_00: And so I think about it that way.
• 7:56
  SPEAKER_00: So immediately, right?
• 7:57
  SPEAKER_00: My mind went to, well, yeah, New York City, lots of people, lots of buildings that have an unbelievable amount of mass, and you just put it like staggering numbers on that, of course it's sinking.
• 8:08
  SPEAKER_00: It made sense, right?
• 8:10
  SPEAKER_00: And I thought, well, it's not just New York, it's every major city is gonna have this kind of thing.
• 8:15
  SPEAKER_00: So that's where my mind went.
• 8:17
  SPEAKER_00: What about you?
• 8:18
  SPEAKER_01: Yeah, so I kind of was like, I kind of had the similar thought through it with a different conclusion, I suppose, because you know, in New York City, if you're a geologist and you've been to New York City, you probably walked around Central Park, and the Manhattan schist is exposed in Central Park.
• 8:33
  SPEAKER_01: And this is bedrock.
• 8:35
  SPEAKER_01: So a lot of the city, or at least substantial part of it, is built right on bedrock, at least Manhattan area, where all the big skyscrapers are.
• 8:43
  SPEAKER_01: That's built on bedrock.
• 8:44
  SPEAKER_01: And so I was kind of like, hmm, uh that's interesting.
• 8:46
  SPEAKER_01: I I I don't know.
• 8:48
  SPEAKER_01: Maybe it is sinking under maybe it is sinking under its weight.
• 8:50
  SPEAKER_01: So I was I was I was kind of like thinking, oh, this is interesting.
• 8:53
  SPEAKER_01: I I need to read more into this.
• 8:54
  SPEAKER_01: I didn't really have I I thought I was curious, that's for sure, but I didn't have a knee-jerk reaction, maybe.
• 9:00
  SPEAKER_00: Really interesting because uh I think that's important.
• 9:02
  SPEAKER_00: The what you brought up about the schist.
• 9:04
  SPEAKER_00: This is schist is bedrock and it's not very compressible.
• 9:08
  SPEAKER_00: Your thinking is, well, that's really interesting, but New York City really, at least Manhattan should not be sinking because it's sitting right on this really not compressible bedrock.
• 9:19
  SPEAKER_01: And that brings up another really interesting part of this is that the researchers who put this together they had to consider what kind of bedrock or what kind of land are the buildings built on.
• 9:28
  SPEAKER_01: Is it sitting on the bedrock, like Central Park, the Manhattan Schist, or is it sitting on glacial till?
• 9:33
  SPEAKER_01: There's glacial till in the underneath of the five boroughs, or is it sitting on infill, which I didn't know this, that there's a lot of New York City that's built on infill, that the city has just kind of expanded the land area by putting fill in and then building on top of that.
• 9:48
  SPEAKER_01: That stuff is super compressible.
• 9:50
  SPEAKER_01: And so basically, let's let's sort of back up.
• 9:52
  SPEAKER_01: And what the researchers did, they compiled all this data, compiled all the numbers, looked at the underlying geology, and then fed this into subsidence models.
• 10:00
  SPEAKER_01: So basically, models that said how much is that weight going to compress that type of land, whether it be bedrock or others, how much is it going to compress that?
• 10:10
  SPEAKER_01: And then compared that to GPS and geodetic measurements of the ground movement.
• 10:16
  SPEAKER_01: So then compared that to the observed ground movement in the New York City area.
• 10:21
  SPEAKER_01: That's kind of you know what they did here.
• 10:24
  SPEAKER_00: Okay.
• 10:24
  SPEAKER_00: That's a really interesting thing.
• 10:26
  SPEAKER_00: So basically, what you're saying is the authors didn't really say that New York City is sinking due to its own mass or due to the mass that we've put there.
• 10:38
  SPEAKER_01: This is an interesting exercise, Chris, because I I think you um, as we're putting together, especially Camp Geo, you always give me a hard time for hedging so much.
• 10:47
  SPEAKER_01: And I'm always hedging, especially on this podcast, right?
• 10:49
  SPEAKER_01: I'm like, oh yeah, yeah, it's this, but.
• 10:51
  SPEAKER_01: And uh the authors of this article, Reading Between the Lines, were doing this as well because in the published article, they don't really say that it's sinking under its own weight.
• 11:02
  SPEAKER_01: In their title of their paper, The Weight of New York City, Possible Contributions to Subsidence from Anthropogenic Sources.
• 11:09
  SPEAKER_01: Basically, I I think my reading of it is that their conclusion is that in these areas where the city is built on infill, there could be a substantial amount of subsidence going on.
• 11:20
  SPEAKER_01: And New York City is sinking at a rate of about one to two millimeters per year.
• 11:25
  SPEAKER_01: That's what we observe.
• 11:26
  SPEAKER_01: And in different parts of the city, some places are sinking faster, which again could be due to this infill.
• 11:31
  SPEAKER_01: But actually, the whole region, meaning from New York City all the way down to the Carolinas, is sinking at a rate of a couple millimeters per year, mostly due to glacial relaxation, post-glacial relaxation.
• 11:43
  SPEAKER_00: Can I interrupt you though a second, Jesse?
• 11:44
  SPEAKER_00: Because I think that's not as intuitive.
• 11:46
  SPEAKER_00: Let's let's first talk about where isostasy happens geologically or where we can see this kind of going on, right?
• 11:54
  SPEAKER_00: Like, for instance, you look at the Hudson Bay.
• 11:57
  SPEAKER_00: Why is the Hudson Bay there?
• 11:59
  SPEAKER_00: Okay, the Hudson Bay was the zone of accumulation for continental ice sheets during the last ice age.
• 12:06
  SPEAKER_00: That ice was tremendously thick, miles thick.
• 12:09
  SPEAKER_00: And that's the Hudson Bay is where the ice was the thickest.
• 12:12
  SPEAKER_00: That's where it was the heaviest.
• 12:13
  SPEAKER_00: And so as a result, that's where the ground subsided more than anywhere else.
• 12:19
  SPEAKER_00: And so it creates this natural depression, right?
• 12:22
  SPEAKER_00: And so when it's gone, it got invaded, you know, covered with with water, and there you go, you got the Hudson Bay.
• 12:28
  SPEAKER_00: You know, and that's this is why you get rocks that formed really, really deep in the earth, like gneisses and granites.
• 12:36
  SPEAKER_00: How do they get exposed at the surface?
• 12:39
  SPEAKER_00: This is one of the mechanisms for that.
• 12:41
  SPEAKER_01: And so I think, Chris, to explain, you described the Hudson Bay, and this is the classic one.
• 12:46
  SPEAKER_01: You have this glacial weight, and as it's sitting on top of the rocks, all this three kilometers of continental scale glaciers are pushing down.
• 12:53
  SPEAKER_01: Now the glaciers are gone, and the crust is rebounding slower than the glaciers retreated.
• 12:59
  SPEAKER_01: So the glaciers are gone and the crust is slowly rebounding up, and that makes intuitive sense.
• 13:03
  SPEAKER_01: So why is the northeast of the United States sinking, subsiding because of glacial rebound?
• 13:09
  SPEAKER_01: And I'm going to use your analogy.
• 13:11
  SPEAKER_01: I'm going to modify your analogy.
• 13:12
  SPEAKER_01: And your analogy for this is like a shipping container ship where when it's empty, it's floating high.
• 13:18
  SPEAKER_01: When you pile stuff on top of it, it starts to float lower and lower and lower and sink down, right?
• 13:23
  SPEAKER_01: Now, if you take that shipping container ship, take all the containers off it, it's going to rebound up.
• 13:28
  SPEAKER_01: That's like removing the glaciers.
• 13:29
  SPEAKER_01: Instead of that, I'm going to take the really, really long shipping container ships, super long ones.
• 13:35
  SPEAKER_01: And I'm going to put all of the weight on the back end, put all of the shipping container weight, really, really heavy stuff.
• 13:42
  SPEAKER_01: Like we're going to put tons of really heavy stuff right on the back.
• 13:45
  SPEAKER_01: And the front is going to tip up, right?
• 13:47
  SPEAKER_01: When you sort of sink the back of the ship, the front's going to kind of tip up a little bit.
• 13:51
  SPEAKER_01: That's what happened when the glaciers were in North America.
• 13:54
  SPEAKER_01: When the glaciers were up north, the south, the New York City and South to the Carolinas was kind of tipped up.
• 14:00
  SPEAKER_01: Now the glaciers are removed.
• 14:02
  SPEAKER_01: We took all that stuff off, and the ship is kind of leveling back out, right?
• 14:06
  SPEAKER_01: And so the New England area and down to the Carolinas is subsiding because of that post-glacial relaxation of what's called the four bulge, that the nose of the ship tipping up would be the four bulge.
• 14:17
  SPEAKER_01: And so that explains most of the regional subsidence.
• 14:21
  SPEAKER_01: And I think it's an important thing to think about when we talk about sea level rise.
• 14:25
  SPEAKER_01: The sea level is rising in a particular area, not just because the ocean's rising up, but the land could be sinking.
• 14:30
  SPEAKER_01: And these two things go hand in hand, like the sinking of the land and the rising of the water due to climate change.
• 14:36
  SPEAKER_01: Those can make any problems with sea level rise much more dramatic, I guess.
• 14:40
  SPEAKER_00: Um, Jesse, you nailed it.
• 14:44
  SPEAKER_00: That analogy might that was great, actually.
• 14:48
  SPEAKER_00: Really, really well done on that.
• 14:49
  SPEAKER_00: I because that makes sense.
• 14:51
  SPEAKER_00: I think anybody can understand that.
• 14:53
  SPEAKER_00: Good job.
• 14:54
  SPEAKER_00: Yeah, that was awesome.
• 14:55
  SPEAKER_00: Yeah.
• 14:55
  SPEAKER_00: Well, I think um this was a cool, it was a cool article.
• 14:59
  SPEAKER_00: Catchy title.
• 15:00
  SPEAKER_00: Catchy title, man.
• 15:01
  SPEAKER_01: Yeah, it's a catchy title.
• 15:02
  SPEAKER_01: It was it was worth a read.
• 15:03
  SPEAKER_01: Yeah.
• 15:03
  SPEAKER_01: And hey, once again, geoscience making news.
• 15:07
  SPEAKER_01: Oh, so good.
• 15:08
  SPEAKER_01: So cool.
• 15:09
  SPEAKER_01: Excellent stuff.
• 15:09
  SPEAKER_01: Hey, if you want to learn all the basics of geology, just like you would if you were sitting in Chris Bull Heis's basically AP geology class or my intro to physical geology at Penn State, you can go to geo.campcourses.com.
• 15:21
  SPEAKER_01: It's the first link in your show notes.
• 15:22
  SPEAKER_01: That's the Camp Geo.
• 15:24
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• 15:29
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• 15:29
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• 15:33
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• 15:34
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• 15:35
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• 15:44
  SPEAKER_01: Cheers.
• 15:44
  SPEAKER_01: Peace.