Speaker 1: Hey, are you welcome to Stuff to Blow your Mind?
Speaker 1: My name is Robert Lamb and I'm Joe McCormick, and
Speaker 1: today we're bringing you an episode from the vault. This
Speaker 1: is our part one of our episode on sink Holes,
Speaker 1: which originally aired on January. We hope you enjoy Welcome
Speaker 1: to Stuff to Blow Your Mind production of My Heart Radio.
Speaker 1: Hey you welcome to Stuff to Blow your Mind. My
Speaker 1: name is Robert Lamb and I'm Joe McCormick, and today
Speaker 1: we're gonna be talking about sink holes. This is actually,
Speaker 1: I think, in a way a listener request topic that
Speaker 1: turned out to be very interesting. But it's, uh, it's
Speaker 1: sort of leap frogging off of some some previous episodes
Speaker 1: we did. Rob did the did the sink Whole journey
Speaker 1: begin when we were talking about the star Lac from
Speaker 1: Return of the Jedi. I think that is the original context.
Speaker 1: I think that was the original point at which we
Speaker 1: begin to hear listener males about the idea of in
Speaker 1: a sink Whole episode, because we talked about the star
Speaker 1: Lac and then we talked about some ideas and was
Speaker 1: it meso American uh? Mythology concerning uh entities of the
Speaker 1: ground that swallow things up. Oh, that could be it. Well,
Speaker 1: I know we ended up talking about the Bible, which
Speaker 1: will revisit in a minute here. But one of the
Speaker 1: questions that came up was, you know that scene in
Speaker 1: movies where there's an earthquake and and then suddenly a
Speaker 1: crack opens up in the middle of the street and
Speaker 1: it's you know, miles deep, and it just swallows people
Speaker 1: down into it. Uh. The question was like, does that
Speaker 1: kind of thing really happen? Does during an earthquake? Does
Speaker 1: the earth open up and open these deep pits and
Speaker 1: chasms that people fall down and disappear into. And our
Speaker 1: previous answer to that was, well, not really, or it
Speaker 1: seems like that's that's extremely rare if it ever happens.
Speaker 1: That's not like a common feature of what happens to
Speaker 1: the surf is topology during an earthquake. But sinkholes, a
Speaker 1: listener pointed out, or a very different story, and sinkholes
Speaker 1: could explain many of these stories, uh, from from mythology
Speaker 1: and all that of the earth opening up and swallowing people.
Speaker 1: We can get back into that in a bit. But
Speaker 1: you actually turned up a really interesting photo essay about
Speaker 1: a fascinating sudden opening of a sinkhole. Uh just earlier
Speaker 1: this year, that's right. Well, actually it was last year, remember,
Speaker 1: oh god, Yeah, I haven't turned the calendar fully yet.
Speaker 1: It's still it's still It's like that year is kind
Speaker 1: of like the the other world in hell Raisers. So
Speaker 1: it's got chains with hooks and them, and they shoot
Speaker 1: out of the walls and so the hooks are still
Speaker 1: in my brain, but I'm slowly methodically rebuilding my body
Speaker 1: to escape. All right, Well, this is this story takes
Speaker 1: us back to April. So Um. What happened is a
Speaker 1: whole opened up in the front yard of a home
Speaker 1: in Black Hawks, South Dakota. Uh, specifically in a housing
Speaker 1: development there that is called perfectly enough, the Hideaway Hills development.
Speaker 1: That just doesn't sound great. I mean no offense to
Speaker 1: the people who live there, but it doesn't sound like
Speaker 1: a place I want to go. It sounds like a
Speaker 1: place where, I don't know, where you like retreat after
Speaker 1: you've committed a crime. What was the housing development on
Speaker 1: arrested development, Sudden Valley or Sudden Yeah Appa, so Um,
Speaker 1: Like you pointed out, there's an incredible photo essay photos
Speaker 1: series on this on board Panda about this. If you
Speaker 1: look up board Panda Black South Dakota sinkhole, you will
Speaker 1: find it because uh this photo essay, if you will,
Speaker 1: it takes us through a journey by a local caving
Speaker 1: group called Pahsapa Grotto as they decided to venture down
Speaker 1: into this hole that opened up in this front yard
Speaker 1: to explore the world beneath the suburbs. Now, this sinkhole,
Speaker 1: it turns out it's going to be very different than
Speaker 1: most of the sinkholes we're talking about in this episode.
Speaker 1: Most sink holes open up over some kind of void
Speaker 1: that is formed in the rock below, and as we'll
Speaker 1: get into a lot of that usually has to do
Speaker 1: with water and hydrology. But in this case, the void
Speaker 1: in the rock below the neighborhood was was more was
Speaker 1: of a more artificial persuasion, right. That's because there was
Speaker 1: an abandoned gypsum mine beneath the housing development, and so
Speaker 1: the cavers had they had to lower down in on ropes,
Speaker 1: you know, had to use like actual caving equipment into
Speaker 1: the dark and sometimes flooded tunnels beneath reportedly over two
Speaker 1: thousand feet across in a hundred and fifty feet wide
Speaker 1: this tunnel um complex. Uh, and they encountered the remains
Speaker 1: of what looks like an old, like nineteen fifties automobile. Uh.
Speaker 1: There's just a whole world down there, like a whole
Speaker 1: uh Minoan maze beneath this you know, rather mundane looking
Speaker 1: housing development. It's like two levels of weird. So first
Speaker 1: of all, it's yes, the suburban you know, neighborhood, and
Speaker 1: then just in the middle of somebody's front yard a
Speaker 1: pit opens up, so that's the sinkhole. But then it's
Speaker 1: that the sinkhole goes to this maze. And yeah, like
Speaker 1: you said, there's like an old Chevy convertible down there,
Speaker 1: And I'm wondering, why is that down there? Did somebody
Speaker 1: drive it into the mind before the mind was sealed up? Yeah,
Speaker 1: I don't know. Like, it's just it's a place full
Speaker 1: of questions, is a place full of the past, of mysteries.
Speaker 1: And so the article itself gets into some of the
Speaker 1: community fall out over all this. But but what I
Speaker 1: love about this episode is it illustrates for us this
Speaker 1: divide between the surface world so tightly manicured and controlled
Speaker 1: so much of the time, and a world beneath that
Speaker 1: we have only a shaky understanding of like something out
Speaker 1: of a mash up between Poltergeist and The Descent. You know,
Speaker 1: a gateway to that hidden underworld might open up at
Speaker 1: any moment and reveal its secrets to us, invite us in,
Speaker 1: perhaps swallow us entirely, and then we'll be part of
Speaker 1: that underworld. Because if we're being you know, perfectly rational
Speaker 1: without any supernatural ideas like that, that idea alone is terrifying.
Speaker 1: You know that the earth might open up and we
Speaker 1: might fall, you know, into a pit. But then if
Speaker 1: you begin to layer in beliefs and superstitions, then yeah,
Speaker 1: become this whole becomes a portal to other realms. Yeah, exactly.
Speaker 1: Now we've talked about natural features in the landscape taking
Speaker 1: on religious significance before, Like in we did a couple
Speaker 1: of episodes called The Sacred Mountain, which was about mountain
Speaker 1: peaks that were considered to be holy or supernatural or
Speaker 1: the dwelling places of gods or places that Win explored.
Speaker 1: People often reported having supernatural experiences, They're like One of
Speaker 1: the things that came out of that was the the
Speaker 1: often reported third man syndrome, feeling that mountain climbers sometimes
Speaker 1: have very high up but we talked about possible ways that,
Speaker 1: like the effects of the sun or that altitude sickness
Speaker 1: could contribute to that um. But there are also ways
Speaker 1: in which sinkholes can take on similar types of religious significance,
Speaker 1: can have a similar mythological appeal, And one great example
Speaker 1: is we is some of the sinkholes are also known
Speaker 1: as sinnotes that we see throughout Mesoamerican religion in the
Speaker 1: Yucatan Peninsula and among the ancient Mayan people. But I
Speaker 1: guess well, we'll come back to that more later. I
Speaker 1: wanted to get to this question about the the idea
Speaker 1: that the earth can open up and swallow you. It's
Speaker 1: an image that seems like to perfectly fit ancient myths
Speaker 1: and texts. You would imagine passages like this appearing in
Speaker 1: you know, Babylonian texts or something. It definitely appears in
Speaker 1: the Hebrew Bible, for example, in the Book of Numbers,
Speaker 1: there's a passage where Moses is speaking to people and
Speaker 1: he's trying to demonstrate that he was in fact sent
Speaker 1: by the Lord and he uh he, he says, and
Speaker 1: basically he makes a promise that hey, if the Lord
Speaker 1: has sent me he'll he'll send a sign, and you'll
Speaker 1: know it, because there will be this group of people
Speaker 1: that will be swallowed up alive into a pit that
Speaker 1: opens up suddenly in the earth. For very these wicked
Speaker 1: people who have rejected the Lord. And the passage says
Speaker 1: in Uh in the Book of Numbers. Now it came
Speaker 1: to pass, as he finished speaking all these words, that
Speaker 1: the ground split apart under them, and the earth opened
Speaker 1: its mouth and swallowed them up with their households, and
Speaker 1: all the men of Cora, with all their goods. So
Speaker 1: they and all those with them went down alive into
Speaker 1: the pit. The earth closed over them, and they perished
Speaker 1: from among the assembly. And so I wonder, I mean, obviously,
Speaker 1: with passages like this, I wonder if it's this kind
Speaker 1: of thing that inspired that scene in every movie that
Speaker 1: has an earthquake in it where suddenly a bottomless pit
Speaker 1: opens up in the ground and people get sucked into it. Yeah,
Speaker 1: you know, this could also be graboids. If I think,
Speaker 1: if they want to make another Tremor's film, which they will,
Speaker 1: I'm sure they should go for you know, some biblical
Speaker 1: flare here, go for an Old Testament Tremor's movie with
Speaker 1: with Moses being our central character, and that's a very
Speaker 1: good direction. Now, one thing I want to say, because
Speaker 1: I feel like I have to bring this up every
Speaker 1: time we talk about geo mythology. Uh, there's this question
Speaker 1: of is this story in the Bible based on something
Speaker 1: that someone in history witnessed witnessing a real world geological event,
Speaker 1: perhaps a sudden collapse of a settled area due to
Speaker 1: a sinkhole. Uh. And as I pretty much always do
Speaker 1: whenever we talk about geomethology, I want to emphasize that
Speaker 1: fantastic imagery and in myths and legends and religious text
Speaker 1: doesn't necessarily need to be explained by someone actually having
Speaker 1: seen something physical in the world. I think we can
Speaker 1: sometimes go overboard looking for naturalistic explanations of this kind
Speaker 1: to explain what somebody thought they saw that appears in
Speaker 1: a story. You know, people are highly imaginative, and sometimes
Speaker 1: stories are just stories. But there's always also the possibility
Speaker 1: that stories like these could be based on people hearing
Speaker 1: stories about having seen I don't know, there was a
Speaker 1: there was a castle or a building or something like
Speaker 1: that that was just swallowed up into the earth, which
Speaker 1: if you didn't have any kind of geological understanding with
Speaker 1: which to to to interpret that. It would certainly seem
Speaker 1: to be a you know, a supernatural event. I don't
Speaker 1: I don't know how else you would interpret it. Yeah,
Speaker 1: because I think one of the things that really drives
Speaker 1: home and when we we see examples of sync holes
Speaker 1: and we hear stories like this, we see cinematic interpretations,
Speaker 1: is that idea that the that terra firma is not
Speaker 1: that firm, is not that fixed, that it could change,
Speaker 1: that the that the firm ground beneath our feet could
Speaker 1: suddenly give way, you know, like that alone is just
Speaker 1: this kind of uh, you know, horrifying idea that that
Speaker 1: it that it easily applies as a metaphor to everything
Speaker 1: else in our in our life. You know, that the
Speaker 1: thing that is the order that we depend upon might
Speaker 1: go away at any moment. Yeah, it's interesting to think about,
Speaker 1: like a vertical spectrum of of ways the natural world
Speaker 1: can intrude on our lives and how most of the
Speaker 1: stuff that we're that we're used to thinking about taking
Speaker 1: into consideration, worrying about as as possible threats, all basically
Speaker 1: takes place like on the surface of the earth. And
Speaker 1: that you know, when you go to the vertical ends
Speaker 1: of that spectrum, you've got like impacts from space coming
Speaker 1: from above, sinkholes up and opening up from below, and
Speaker 1: these fen I'm gonna intrude on that day to day
Speaker 1: understanding of physical forces. Yeah, so it's it's no surprise.
Speaker 1: We were talking about this before the podcast started rolling
Speaker 1: here that if you start looking around for sinkholes online,
Speaker 1: you'll find just so many galleries, top ten lists, lots
Speaker 1: of click bait about sinkholes. Like sinkholes are kind of
Speaker 1: they're kind of like a like they're kind of like
Speaker 1: true crime, you know there um there. You also see them,
Speaker 1: like I was noticing, like very tabloid sites sites that
Speaker 1: otherwise they're not going to really have anything related to geology,
Speaker 1: but they'll have sinkholes. You know, it'll be celebrity gossip,
Speaker 1: um and you know, maybe some conspiracy theories. But then also, uh,
Speaker 1: big old holes opening up in the earth. Chump boxes
Speaker 1: are full of sinkholes. Have you ever noticed this? These
Speaker 1: are the like the link um grids at the bottom
Speaker 1: of blogs and whatnot. Yeah. Yeah, so, like you know,
Speaker 1: like most websites on the Internet these days are just
Speaker 1: being more and more infected by ads that a since
Speaker 1: really take the form of malware. But if you scroll
Speaker 1: down to the bottom of most articles or any text
Speaker 1: image based website, you'll usually see one of these boxes
Speaker 1: that's full of just like extremely tacky, distasteful images that
Speaker 1: are either like something that's kind of sexually suggestive and
Speaker 1: a gross way, or something that is uh sort has
Speaker 1: some kind of like health vibe, Like it looks like
Speaker 1: infected skin or holes in skin, or some kind of
Speaker 1: bite or something like the kind of a necrotic bite
Speaker 1: that you might imagine someone would get in their worst
Speaker 1: nightmares from a brown recluse, you know that kind of thing. Um. Yeah,
Speaker 1: they they tie into our like deepest, most primal fears
Speaker 1: and desires, just pure eroticism or just pure in necrotic
Speaker 1: damage or indeed holes opening up in the earth. You know,
Speaker 1: it's got to be something extreme like that to make
Speaker 1: it into that grid of horror. Yeah. The toilet with
Speaker 1: the rat coming up through it, remember that one. Oh,
Speaker 1: I think I've seen that when I was a common
Speaker 1: chumbox image or the like. You know, doctors say never
Speaker 1: eat this vegetable, but they don't tell you what it is. Yeah, yeah, yeah,
Speaker 1: sometimes it is. Um. It. It's economic as well. You know,
Speaker 1: there'll be some sort generally it's like a picture of
Speaker 1: an old person and just a few like alarming words
Speaker 1: about you know, investments and retirement or something. Right, but
Speaker 1: that is the world. Well, sinkholes are actually in their
Speaker 1: own way. I mean, of course they can be horrifying,
Speaker 1: they can be destructive to human life, but they are
Speaker 1: also fascinating in their own way. In the natural way,
Speaker 1: they are wonderful. Uh. There can be beautiful uh legends
Speaker 1: and stories attached to them, and so I don't know,
Speaker 1: I feel like they are the most uh naturally beautiful
Speaker 1: thing that that fits in the chum box. I mean
Speaker 1: the rat and the toilet can't compete. I mean the
Speaker 1: rat and the toilet. We could do an episode on
Speaker 1: that as well. But yeah, I agree, the sinkholes need
Speaker 1: to be rescued from the chum box. Uh. And and
Speaker 1: that's kind of what we're doing in in this episode
Speaker 1: of Stuff to Blow Your Mind and the possible second
Speaker 1: episode of Follan. Alright, so sinkholes are formed in a
Speaker 1: number of ways, but most naturally occurring sinkholes, like most
Speaker 1: other things on planet Earth, in the end, come back
Speaker 1: to the power of water. Water, of course, is the
Speaker 1: molecule of life, largely because of its power as a
Speaker 1: master solvent, and in much the same way really that
Speaker 1: water created life on Earth, probably it also creates many
Speaker 1: of Earth's most astounding geologic features. And so this is
Speaker 1: how we we get sinkholes for the most part. So
Speaker 1: as carbon dioxide in the air or in the soil
Speaker 1: mixes with rain water, that mixture forms a weak acid
Speaker 1: with the with the chemical formula H two c O three.
Speaker 1: So what you've got there is you've got your H
Speaker 1: two oh the water, and then you've got your C
Speaker 1: O two the carbon dioxide. They react, they make a
Speaker 1: compound with two hydrogens, one carbon and three oxygen's. And
Speaker 1: this weak acid formed in the atmosphere or in the
Speaker 1: soil is known as carbonic acid, and it is the
Speaker 1: primary reason that caves exist. Now most caves in the world,
Speaker 1: not all, but most are formed by the drainage of
Speaker 1: acidified water through what you might call soluble rock and uh.
Speaker 1: Soluble rock are types of rock that can react chemically
Speaker 1: with this water and be dissolved and carried away. Now
Speaker 1: they're they're multiple kinds of soluble rock, including minerals like
Speaker 1: salt and gypsum, But probably the most important, or at
Speaker 1: least the most charismatic, is limestone, which is in itself
Speaker 1: a fascinating and even mind boggling rock. And sometimes I
Speaker 1: really do think a lot about limestone, and maybe people
Speaker 1: are aren't inclined to be as impressed by it as
Speaker 1: I am. But if you don't believe me that limestone
Speaker 1: is amazing, I think it's worth considering that if you
Speaker 1: live in an area of the world you know this
Speaker 1: primary resting on limestone, which in the United States would
Speaker 1: include huge portions of like Florida and the coastal southeast,
Speaker 1: big parts of the Midwest. If you live in a
Speaker 1: place like that dominated by this this carbonate rock, you
Speaker 1: are walking around every day on rock that is probably
Speaker 1: mostly built out of dead bodies. Limestone can be formed
Speaker 1: in a number of ways. Some of those ways are
Speaker 1: a biotic, but one of the major processes that forms
Speaker 1: limestone is the gradual deposition of the shells and other
Speaker 1: hard calcium carbonate body parts of animals and other tiny
Speaker 1: organisms in the oceans and rivers and lakes where they
Speaker 1: accumulate on the bottoms of these water sources over millions
Speaker 1: of years, and apparently feces also in general, waste products
Speaker 1: can contribute as well. So the calcium based body parts
Speaker 1: of algae and coral and oysters and all kinds of
Speaker 1: creatures of the sea settle in the deep, and then
Speaker 1: they're pressed down and paved over by time and pressure
Speaker 1: until they become layers of sedimentary rock. I really just
Speaker 1: think about that. Sometimes limestone is largely made out of
Speaker 1: life that has died and become rock, like the fallen
Speaker 1: creatures of Earth pile up and become part of the
Speaker 1: crust of the Earth itself. Wow, it's like it's like
Speaker 1: the Medusa's layer, right, all these like the petrified bodies. Oh,
Speaker 1: that's I wish I had thought of that when we
Speaker 1: were doing our Medusa episodes. Except I guess in the
Speaker 1: Medusa Garden that they keep their form right here. They
Speaker 1: just sort of like go back to whence they came.
Speaker 1: They become part of this mass. But anyway, it's via
Speaker 1: rocks like this that we get so many of the
Speaker 1: naturally occurring sinkholes on the Earth. So how do they form? Well,
Speaker 1: imagine that there is a storm, it rains here in
Speaker 1: an area with some kind of soluble rock. Let's say
Speaker 1: it's a it's a carbonate rock, it's like limestone, and
Speaker 1: rainwater collects on the surface of the earth and then
Speaker 1: runs downhill. And if that rainwater drains down in two
Speaker 1: cracks insoluble rock like limestone, things begin to happen much
Speaker 1: in the same way that you can dissolve table salt
Speaker 1: or sugar and a glass of water. The crystal contents
Speaker 1: of these soluble rock surfaces are gradually dissolved in and
Speaker 1: carried away by that acidified water. And over tens or
Speaker 1: hundreds of thousands of years, that dissolution of the rock
Speaker 1: by acidic water can turn what might have started as
Speaker 1: this tiny stress fracture in a chunk of bedrock into
Speaker 1: an underground cavern large enough for a human to climb into.
Speaker 1: And of course, as the centuries go on, these these
Speaker 1: voids created by the drainage pathways of water can just
Speaker 1: get bigger and bigger. They can form underground rivers that
Speaker 1: form larger and larger voids. And it's this dissolution of
Speaker 1: soluble rock by water that usually leads to the creation
Speaker 1: of sinkholes. Uh though these voids in the rock, I
Speaker 1: think sometimes maybe geologists will get picky about this, these
Speaker 1: voids in the rock are not technically themselves sinkhole, and
Speaker 1: we would normally think of them as voids or just
Speaker 1: caves right there, their caves in the rock. Um. Rather,
Speaker 1: a sinkhole is more of a topographical designation. It's a
Speaker 1: topographical concept about the ground and the surface of the earth.
Speaker 1: So according to the U S Geological Survey, a sinkhole
Speaker 1: is quote an area of ground that has no natural
Speaker 1: external surface drainage. So like in one of these areas,
Speaker 1: if it rains, water just pools in and there's nowhere
Speaker 1: on the surface level that allows this water to run out.
Speaker 1: So if the water leaves, it's either evaporating into the
Speaker 1: air or it's draining out through somewhere in the bottom. Sinkholes,
Speaker 1: of course, can form gradually over hundreds or hundreds of
Speaker 1: thousands of years, often of steady dissolution, or they can
Speaker 1: form quite suddenly. For example, when the ground over a
Speaker 1: void in the limestone below is suddenly just suddenly there's
Speaker 1: not enough for it to support its own weight, and
Speaker 1: then it just collapses and reveals the void that had
Speaker 1: been there for so long. Uh. And we know that
Speaker 1: the sudden appearance of a sinkhole can have these devastating
Speaker 1: effects on human settlements and uh whatever is lying on
Speaker 1: the surface, which will get into more later, but it
Speaker 1: can also have strange, otherworldly effects simply on the geological
Speaker 1: and hydrological landscape itself. And I wanted to share one
Speaker 1: amazing example that I came across while I was reading
Speaker 1: up for this episode. This was the opening paragraph in
Speaker 1: an article for The New Yorker by David Owen. There
Speaker 1: was an article about sinkholes called Notes from Underground, and this,
Speaker 1: this paragraph really gave me chills when I got to
Speaker 1: the end of it. So, uh, if you don't mind,
Speaker 1: I just want to share this here. In the fall
Speaker 1: of nine, much of Lake Jackson, a four thousand acre
Speaker 1: natural body of water just north of Tallahassee and a
Speaker 1: popular site for fishing, water skiing, and recreational boating, disappeared
Speaker 1: down a hole like a bathtub, emptying into a drain trophy.
Speaker 1: Bass became stranded in rapidly shrinking eddies, enabling children to
Speaker 1: catch them with their hands and toss them into picnic coolers,
Speaker 1: and many of the lake's other fish, turtles, snakes, and
Speaker 1: alligators vanished into the earth at various times. During the
Speaker 1: next few years, the lake partially refilled, redrained, and refilled again.
Speaker 1: Jonathan Arthur, who is Florida's state geologist and the director
Speaker 1: of the Florida Geological Survey, was among several people who,
Speaker 1: during a dry period descended a ladder into the main opening,
Speaker 1: which was about eight feet in diameter. Quote, you could
Speaker 1: climb down twelve feet or so and then walk under
Speaker 1: the lake bed. He told me recently, I hadn't gone
Speaker 1: very far before my red flags went up, and I
Speaker 1: was like, maybe I won't go any farther. So that image,
Speaker 1: it combined with the way it's phrase that that really
Speaker 1: gave me goose bumps. Yeah. Yeah, the idea of yeah,
Speaker 1: I mean, it really feels like like a place you
Speaker 1: do not belong. The you know, the the cave beneath
Speaker 1: the lake that is uh yeah, that that that could
Speaker 1: potentially fill back up at any moment. Well. And also,
Speaker 1: I mean, I think anybody who, especially people who do
Speaker 1: like scuba diving and stuff, are made uniquely aware of
Speaker 1: the dangers of of being in places that combine water
Speaker 1: and overhead rock. Like Yes, absolutely that that can be
Speaker 1: an especially dangerous and and suddenly dangerous surprisingly dangerous combination
Speaker 1: of features. Yeah, I mean, even if you are an
Speaker 1: experience cave diver, cave diving is dangerous. Uh so um so, yeah,
Speaker 1: that is a dangerous realm to to go down into,
Speaker 1: for sure. Now, I figured it would be worth talking
Speaker 1: about a few of the different ways that natural sinkholes form. Um. Obviously,
Speaker 1: things will be a little bit different if you're talking
Speaker 1: about sinkholes, you know, created by human activity, though human
Speaker 1: activity can also contribute to some of the things I'm
Speaker 1: about to talk about. But but if you're talking about
Speaker 1: natural sinkholes in a carbonate rock like limestone. Um. There
Speaker 1: are three main pathways that were highlighted in uh in
Speaker 1: several sources, in my major source here just being the U. S.
Speaker 1: Geological Survey, who has great materials about this, um and
Speaker 1: so the first one is dissolution sinkholes. These are relatively
Speaker 1: gentle sinkholes. You can think of it as a kind
Speaker 1: of top down sinkhole. Here, what you should picture is
Speaker 1: that you've got a thin layer of what would be
Speaker 1: called overburden, and overburden just means whatever stuff's on top
Speaker 1: of the rock that makes up the ground. So this
Speaker 1: means soil could be sand, could be clay, pebbles, rocks,
Speaker 1: other material resting on top of the rock layer on
Speaker 1: the surface. Now, in a dissolution sinkhole, rain comes down
Speaker 1: and it collects in a depression in the soluble rock
Speaker 1: and just continues to dissolve and deepen that depression over
Speaker 1: time as water gradually percolates down into cracks or joints
Speaker 1: in the rock below. These tend to form very gradually,
Speaker 1: so you can picture kind of a a gentle sort
Speaker 1: of dip or pond in the rock that water is
Speaker 1: going into, and slowly, over time it's draining down into
Speaker 1: the rock below through some cracks or other types of openings,
Speaker 1: and as it does so, it is dissolving more and
Speaker 1: more of the rock and carrying it away. The next
Speaker 1: type would be cover subsidence sinkholes, and this is where
Speaker 1: you've got a lower level of soluble rock that gets
Speaker 1: dissolved by the process we've already talked about, you know,
Speaker 1: water running through it opening up a void in the rock.
Speaker 1: And in this case, if the soil or overburden that
Speaker 1: is above that layer of rock has certain physical characteristics,
Speaker 1: I think, especially if it's like a more free flowing
Speaker 1: kind of granular sediment like sand. Basically, the overburden or
Speaker 1: the soil above kind of gradually pours down into the
Speaker 1: void that opens up. You can imagine it being kind
Speaker 1: of like sand pouring down from the top half of
Speaker 1: an hour glass into the bottom half, and and that
Speaker 1: that overburden pours down fills the void up partially. But
Speaker 1: as it does so, it's sort of like creates a depression,
Speaker 1: of visible depression in the surface of the overburden. And
Speaker 1: these types of pits tend to develop pretty gradually and
Speaker 1: not be all that deep or all that dangerous. Right,
Speaker 1: You've probably seen pits like this before. You're just walking
Speaker 1: through a field and suddenly there's just a depression in
Speaker 1: the ground. Very possibly what's going on there is this
Speaker 1: cover substance sinkhole. The soil is just kind of draining
Speaker 1: into a void in the rock below. Now, of course,
Speaker 1: it's worth noting in all of this, even these milder
Speaker 1: forms of the sinkhole can certainly be destructive if you
Speaker 1: have some sort of humanum structure built atop of it,
Speaker 1: or a road, etcetera, which is sometimes the case, right,
Speaker 1: But these first two have the benefit of not being sudden.
Speaker 1: You know that they're going to take time to develop.
Speaker 1: The third category, this is the real monster that could
Speaker 1: inspire the geo myth potentially. This is the cover collapse, sinkhole,
Speaker 1: and these are the ones that can potentially happen in
Speaker 1: an instant and at least in the United States, they
Speaker 1: tend to be most common in places where the overburden
Speaker 1: is mostly clay. So again, you start the same way
Speaker 1: that the last one did. Avoid opens up in the
Speaker 1: underlying layer of soluble rock, and then the lower levels
Speaker 1: of the overburden gradually drained down into the cavity in
Speaker 1: the rock. And as this happens, what you get is
Speaker 1: a cavity gradually opening up from from below and climbing
Speaker 1: up into the overburden or the soil itself. So imagine again,
Speaker 1: you've got to rock with a cavity or avoid in it,
Speaker 1: and then maybe a layer of clay, and so the
Speaker 1: clay on the bottom starts to seep down into that
Speaker 1: cavern below and it just opens up a bigger and
Speaker 1: bigger void in the clay. And eventually what's going to
Speaker 1: happen there is that that void in the clay reaches
Speaker 1: a point where where the collapsing roof of the void
Speaker 1: breaches the surface, which means whatever is on the surface
Speaker 1: falls into the hole. And that surface might well be
Speaker 1: a road or a lake bed, or the ground under
Speaker 1: a building. And this is the example where we can
Speaker 1: see sudden collapses that can be deadly and destructive and
Speaker 1: terrifying because suddenly what you thought was solid ground is
Speaker 1: revealed to have long had had to void beneath it,
Speaker 1: and suddenly it can't support whatever is on it anymore,
Speaker 1: and it all goes down into the void. It's basically
Speaker 1: like a trap door effect. You know, that's the that's
Speaker 1: the terrifying part about it. You know, that's like suddenly
Speaker 1: there is this opening beneath this and and people, you know,
Speaker 1: can can build things without having any idea that that's
Speaker 1: what's down there. Yeah, I mean, we've we've gotten to
Speaker 1: the point where if we know what we're looking for,
Speaker 1: especially you know, we we have more tools at our disposal,
Speaker 1: uh for detecting sink holes and potential sink holes, and
Speaker 1: in keeping track of of existing sink holes that maybe
Speaker 1: expanding but but expanding have expanded. But yeah, for the
Speaker 1: most part, like that that the the idea here is
Speaker 1: that you don't know what's going to happen, and then
Speaker 1: suddenly there's this chasm there in the earth. Now. Another
Speaker 1: thing that's interesting to me about sinkholes is that we
Speaker 1: often think about geological events like earthquakes and volcanoes as
Speaker 1: what people sometimes call acts of God, you know, natural
Speaker 1: events that occur for reasons vastly beyond our control and
Speaker 1: that we can do nothing to stop. But there is
Speaker 1: some indication that human activity may have more impact on
Speaker 1: some massive geological events than once thought, and it certainly
Speaker 1: appears to have an effect on the proliferation of sinkholes
Speaker 1: in particular. In other words, sinkhole collapses can it seems
Speaker 1: absolutely be invited by human behavior, as will probably discuss
Speaker 1: more as we go on, but in broad strokes, it
Speaker 1: appears that sinkhole collapses can be induced by uh. So,
Speaker 1: one thing is human construction and other changes in the
Speaker 1: top level terrain, especially how that affects water drainage. So
Speaker 1: you're moving earth around and changing the way that water
Speaker 1: drains on the surface. That can lead to sinkle collapses.
Speaker 1: But also pumping of groundwater is a huge thing here.
Speaker 1: You pump out groundwater from deep underground uh the pressure
Speaker 1: of the natural water that's in the ground helps keep
Speaker 1: the soil above it in place. So if you take
Speaker 1: that water out, you lower the groundwater level, you can
Speaker 1: cause collapses of the overburden lying over now evacuated aquifer voids.
Speaker 1: Another thing that seems kind of relevant to that story
Speaker 1: you started with. Remember the sinkle collapse that turned out
Speaker 1: to lead to a mine down below in South Dakota.
Speaker 1: The mine was a gypsum mine. So gypsum is a
Speaker 1: major mineral that's that's in the ground there. We've been
Speaker 1: focusing a lot on limestone, but one thing to note
Speaker 1: that I did read also from the U. S Geological
Speaker 1: Survey was that other types of underlying rock layers, such
Speaker 1: as minerals like salt and gypsum, those can sometimes dissolve
Speaker 1: and form voids much fast to than even sedimentary carbonate
Speaker 1: rocks like limestone. So limestone will form these voids with
Speaker 1: water running through it over you know, thousands of years,
Speaker 1: but apparently assault and gypsum, potentially with the right circumstances,
Speaker 1: can form large voids in in a matter of you know,
Speaker 1: days or months. Than well, let's get into some examples
Speaker 1: of sinkholes. Uh. And granted there are so many sinkholes
Speaker 1: that have either existed for you know, thousands of years
Speaker 1: or have just popped up in you know, recent decades.
Speaker 1: But I want to start with one that I imagine
Speaker 1: is instantly coming to a number of your minds. And
Speaker 1: you're you're, especially when we were talking earlier about click
Speaker 1: baity uh sinkholes, and that would be the two thousand
Speaker 1: seven and especially the two thousand ten Guatemala City sinkholes. Um.
Speaker 1: And they're they're worth mentioning for a couple of reasons. So, so,
Speaker 1: first of all, there are some very dramatic photographs of
Speaker 1: this thing. Photographs so dramatic that they they look photoshop.
Speaker 1: You know, they don't look real. Absolutely, it looks like
Speaker 1: something out of a movie. Yeah. It looks like a
Speaker 1: hole has been like a cylindrical hole has been bored
Speaker 1: into this city escape and it just descends into absolute darkness.
Speaker 1: It is. It's a terrifying image. Um. And And and
Speaker 1: when this these occurred, I mean, these were dramatic, traumatic events,
Speaker 1: These were deadly occurrences. That two thousand seven sinkhole killed
Speaker 1: five people and required the evacuation of more than a thousand.
Speaker 1: The two thousand ten sinkhole swallowed a three story factory
Speaker 1: and killed fifteen people. And in both cases, uh, it
Speaker 1: seems to there seemed to have been a at least
Speaker 1: a trio of causes. So there was the impact of
Speaker 1: tropical Storm Agatha as well as the Pacaya volcano eruption,
Speaker 1: but also leakage from sewer pipes and all of this.
Speaker 1: So we're together to erode uncemented volcanic act, limestone and
Speaker 1: other pyroclastic deposits beneath the city. And this case is
Speaker 1: actually so visually alarming. There's a Snopes article about it,
Speaker 1: not because there seems to be like a lot of
Speaker 1: misinformation about the event itself. Uh, but it gets picked
Speaker 1: up continually on social media as if it just happened,
Speaker 1: as if it just happened, you know, this week or today,
Speaker 1: as opposed to a decade ago. Right, So the photo
Speaker 1: is real, the story is real, but it's but what
Speaker 1: needs to be debunked is that people want to just
Speaker 1: like reintroduce it as newly relevant over and over again
Speaker 1: because it will always get attention. It's so dramatic looking. Yeah. Uh.
Speaker 1: There is also a good Atlas Obscure article about it,
Speaker 1: though I have to point out that the Atlas Obscure article.
Speaker 1: I think this is a feature of just things that
Speaker 1: they have cataloged on the site. But it says sorry,
Speaker 1: great Guatemalan sinkhole is permanently closed, which which is it
Speaker 1: is a weird sentence to read. Now. Meanwhile, up here
Speaker 1: in North America we have our own sinkholes of note.
Speaker 1: For instance, there are two giant West Texans sinkholes in
Speaker 1: Wink and Kerment, Texas. They're located about a mile apart,
Speaker 1: and these are similar to the Guatemalan sinkholes, and that
Speaker 1: we have definite uh uh connection to human activities. These
Speaker 1: were caused by oil and gas extraction in the area,
Speaker 1: especially during the heyday of nineteen twenty six through nineteen
Speaker 1: sixty four. Uh Wink Sinc. Number One opened in nineteen
Speaker 1: eighty and Wink Sinc. Number Two open twenty two years
Speaker 1: later in two thousand and two. And I was looking
Speaker 1: at a two thousand sixteen Southern Methodist University study where
Speaker 1: they were they were taking a look at these sinkholes
Speaker 1: and the fact that they seem to be expanding because
Speaker 1: the ground there is still unstable due to changing groundwater
Speaker 1: levels and dissolving minerals um. However, like I said, are
Speaker 1: they were now able to use stuff like satellite monitoring
Speaker 1: to keep a better track of sinkhole development and progress.
Speaker 1: But again, this is a case someone to what we
Speaker 1: were describing earlier, where we've taken stuff out of the
Speaker 1: ground and in doing so we have disrupted like the
Speaker 1: you know, the natural balance of things down they're making uh,
Speaker 1: sinkholes more likely to occur. Looking at a picture of
Speaker 1: the wink sinkholes, Uh, just not as impressive as some
Speaker 1: of these because the water level seems to have been
Speaker 1: filled up pretty close to the top. So it looks
Speaker 1: like just a weird pit in the middle of the
Speaker 1: desert that could be like a lake. It's just you know,
Speaker 1: water in it. But uh, but I imagine if you
Speaker 1: that water were to drained out, it would look pretty
Speaker 1: pretty messed up. Yeah. Plus, the bar is pretty high
Speaker 1: for spectacular looking sinkholes, as we'll continue to see as
Speaker 1: we discuss other sinkholes in the in in this episode
Speaker 1: in the one to follow. Well, so I was wondering,
Speaker 1: what's the what's the deepest known sinkhole on planet Earth? Oh, well,
Speaker 1: if we want to go to the deepest, uh, then
Speaker 1: we have to go to China. That is where we
Speaker 1: encounter China's um. This is the the the Shijia uh
Speaker 1: Tien King or the Heavenly Pit, and it's it's named
Speaker 1: for a nearby village and then uh Tien King just
Speaker 1: means heavenly pit. And it's located near Chuanshing in southwest China.
Speaker 1: It's apparently six hundred and twenty six meters or two
Speaker 1: thousand and fifty four ft long. It is five hundred
Speaker 1: and thirty seven meters or a thousand, six hundred sixty
Speaker 1: two feet wide, and it is between five hundred eleven
Speaker 1: and six hundred and sixty two meters deep or between
Speaker 1: one thousand, six hundred and seventy seven to two thousand,
Speaker 1: one hundred and seventy two ft deep, So it's deep
Speaker 1: that it is an enormous hole. And this is one
Speaker 1: that I recommend looking at pictures of because it's is
Speaker 1: really splendid looking. It's beautiful because it um. You have
Speaker 1: the it's it's you have this this this double um.
Speaker 1: It's like a double pit. There's like the initial pit
Speaker 1: and then the pit below. You have vertical walls going
Speaker 1: down to a little area that tapers off and then
Speaker 1: or vertical walls going down even further that there's some
Speaker 1: rich vegetation around it. Um, it's it's really beautiful to
Speaker 1: look at, and indeed it is a tourist attraction if
Speaker 1: you travel there. There apparently two thousand, eight hundred steps
Speaker 1: constructed that allow visitors to journey all the way down
Speaker 1: to the bottom of that second nested pit, which I
Speaker 1: was reading. I think it takes you're gonna spend like
Speaker 1: a couple of hours doing that. I think I read
Speaker 1: that this is also a limestone pit, and yeah, one
Speaker 1: of the great things about it is pits of the
Speaker 1: size and of of this age. You know, it's been
Speaker 1: around for a long time where the surface life has
Speaker 1: just poured down into it, so you know, it looks
Speaker 1: almost like the forest is spilling into the pit. And
Speaker 1: of course that you know, it's a habitat for many animals.
Speaker 1: I think I saw a report that maybe rare like
Speaker 1: the clouded leopard had been spotted there. I think, oh, interesting. Yeah,
Speaker 1: you see time and time again reading about different sinkholes
Speaker 1: that they inevitably become uh an interesting place to look
Speaker 1: at biodiversity. And we'll get we'll get more into that later.
Speaker 1: But yeah, these are these end up being. You know,
Speaker 1: they're not just especially ones that have been there for
Speaker 1: a considerable amount of time. They're not just holes in
Speaker 1: the earth. They don't remain voids. Nature feels that void,
Speaker 1: and it does so in very remarkable ways. Now, there
Speaker 1: are numerous um heavenly pits in this region of China,
Speaker 1: and I can only imagine that there are some really
Speaker 1: interesting traditions and legends about these geologic features. But I
Speaker 1: have to admit that I could not find any of them,
Speaker 1: at least none that had been translated into English. So
Speaker 1: if anybody out there has that information, I would love
Speaker 1: to hear about it, because a sinkhole like this is
Speaker 1: just it's just too amazing. And it's been around way
Speaker 1: too long. It's been around since ancient times, so there
Speaker 1: have to be some cool traditions and legends regarding its
Speaker 1: origin and things that live there, et cetera. Yeah, like you,
Speaker 1: I was looking for similar things and I couldn't find
Speaker 1: any any any cultural context for it. But I would
Speaker 1: love to if you know out there now there is
Speaker 1: another Chinese sinkhole of note that does have some cool
Speaker 1: legend applied to it, and that is a dragon hole
Speaker 1: in the Paracel Islands. It's nine four feet deep two
Speaker 1: hundred and nine so this is out in the ocean.
Speaker 1: It's also known as the Young Lu Dragon Hole, named
Speaker 1: for the fifteenth century Mean dynasty Young Lu Emperor Um.
Speaker 1: It's also known as the Eye of the South China Sea.
Speaker 1: And the tradition here is that this is where the
Speaker 1: Monkey King Uh Soon Will Kong finds his golden cudgel
Speaker 1: in Journey to the West, So this would be his
Speaker 1: magical staff. If you've ever seen a movie with the
Speaker 1: with the Monkey King in it or seeing images of
Speaker 1: the Monkey King, this is his big, amazing fighting staff.
Speaker 1: So he actually gets it from this pit. Well that
Speaker 1: is that is what that they've sort of taken the
Speaker 1: story and said, oh, this must be the pit, okay,
Speaker 1: because in the story he has to retrieve it from
Speaker 1: the underwater kingdom of of our Guang, the Dragon King
Speaker 1: of the East Sea, and uh yeah, this this amazing
Speaker 1: magical staff, the the compliant golden hooped rod or has
Speaker 1: it also been translated as the as you will gold
Speaker 1: banded cudgel? Um? Oh I see compliant or as you will? Yeah, yeah,
Speaker 1: it's um. They're also there's legends that this may have
Speaker 1: been you the Great's measuring stick for determining the depths
Speaker 1: of the Great Flood, So it has that would make
Speaker 1: sense that you know, that would be underwater because there's
Speaker 1: this connection to the depths, and so anyway, he dives
Speaker 1: down into this hole and retrieves it. Now is this, Uh,
Speaker 1: this is a picture of this pit that you've attached
Speaker 1: here for us to look at. Yes, so again, it's
Speaker 1: out out in the water, and it's just like a
Speaker 1: sudden deep section of the of the water, a hole
Speaker 1: in the sea floor that contains you know, dark depths.
Speaker 1: You may have seen pictures of sinkholes in tropical oceans
Speaker 1: like this before, for example, if you've ever seen a
Speaker 1: picture of the Great Blue Hole, which as I think
Speaker 1: isn't believe. Um, yes, because so the way that looks
Speaker 1: from above is that, yeah, you'll see a sort of
Speaker 1: just ring of dark blue surrounded by much lighter blue. Uh.
Speaker 1: As as I guess that just reflects the sudden difference
Speaker 1: in depth. Yeah, exactly, it's this is very much in
Speaker 1: keeping with the Great Blue Hole, just maybe less dramatic looking,
Speaker 1: but still extremely beautiful. Now in s is reported by
Speaker 1: Danny Lewis for Smithsonian mag dot com researchers discovered uh
Speaker 1: like something like forty nine sinkholes clustered close together while
Speaker 1: serving the chin Ling Bashan Mountains in China's uh Uh
Speaker 1: Shaunzi Province, the largest being one thousand, seven hundred and
Speaker 1: six ft or five hundred and nineteen meters wide and
Speaker 1: a thousand and fifty or three hundred and twenty feet deep.
Speaker 1: So um, yeah, it's uh we keep finding these things,
Speaker 1: you know, or in many cases, rediscovering them, and every
Speaker 1: time discoveries like this you're made. You know, it's not
Speaker 1: just an interesting geologic curio, it's a fresh operatunity to
Speaker 1: gaze back in time to understand geology, biology, and even
Speaker 1: the climate of the region in in times past. Oh yeah,
Speaker 1: because this is an interesting thing. You were pointing out
Speaker 1: when we started looking at this, that sinkholes are often
Speaker 1: used as a kind of scientific time capsule, That there
Speaker 1: are ways that sinkholes can tell us things about the
Speaker 1: past that the surface can't do quite as easily. Absolutely,
Speaker 1: and I think we'll start our next episode by diving
Speaker 1: into that, discussing the ways that sinkholes are are very
Speaker 1: often time capsules that we can unlock that we can
Speaker 1: we can venture into not just to you know, to
Speaker 1: to to be in awe of the of the you know,
Speaker 1: this dramatic environment around us, but to uncover the secrets
Speaker 1: of the Earth and the secrets of the ecosystem. I
Speaker 1: can't wait. We got a lot of cool stuff to
Speaker 1: talk about. Next time we can talk about UH. Sinkholes
Speaker 1: in religions, sinkholes in space, sinkholes as time capsules. It's
Speaker 1: gonna be great, That's right. And in the meantime, if
Speaker 1: you want to check out other episodes of Stuff to
Speaker 1: Blow your Mind, you know where to get them. You
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Speaker 1: Thanks as always, to our excellent audio producer Seth Nicholas Johnson.
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