Speaker 1: Welcome just about to blow your mind the production of
Speaker 1: My Heart Radio. Hey you welcome to stuff to blow
Speaker 1: your mind. My name is Robert Lamb and I'm Joe McCormick,
Speaker 1: and today we're gonna be talking about sink holes. This
Speaker 1: is actually, I think, in a way a listener requests
Speaker 1: topic that turned out to be very interesting. But it's, uh,
Speaker 1: it's sort of leap frogging off of some some previous
Speaker 1: episodes we did. Rob did the did the sink Whole
Speaker 1: journey begin when we were talking about the star Lac
Speaker 1: from Return of the Jedi. I think that was the
Speaker 1: original context. I think that was the original point at
Speaker 1: which we begin to hear listener males about the idea
Speaker 1: of that in a Sink Whole episode, because we talked
Speaker 1: about the star Lac and then we talked about some
Speaker 1: ideas and was it meso American uh mythology concerning uh
Speaker 1: entities of the ground that swallow things up? Oh, that
Speaker 1: could be at well, I know we ended up talking
Speaker 1: about the Bible, which will revisit in a minute here.
Speaker 1: But one of the questions that came up was, you
Speaker 1: know that scene in movies where there's an earthquake and
Speaker 1: and then suddenly a crack opens up in the middle
Speaker 1: of the street and it's you know, miles deep, and
Speaker 1: it just swallows people down into it. Uh. The question
Speaker 1: was like, does that kind of thing really happen? Does
Speaker 1: during an earthquake? Does the earth open up and open
Speaker 1: these deep pits and chasms that people fall down and
Speaker 1: disappear into. And our previous answer to that was, well,
Speaker 1: not really, or it seems like that's that's extremely rare
Speaker 1: if it ever happens. That's not like a common feature
Speaker 1: of what happens to the surface topology during an earthquake.
Speaker 1: But sinkholes, a listener pointed out, or a very different story.
Speaker 1: And sinkholes could explain many of these stories, uh, from
Speaker 1: from mythology and all that of the earth opening up
Speaker 1: and swallowing people. We can get back into that in
Speaker 1: a bit. But you actually turned up a really interesting
Speaker 1: photo essay about a fascinating sudden opening of a sinkhole. Uh,
Speaker 1: just earlier this year, that's right, Well, actually it was
Speaker 1: last year. 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 was called, perfectly enough, the Hideaway Hills development.
Speaker 1: That just doesn't sound great. I mean, no offense the
Speaker 1: people who lived there, but it doesn't sound like a
Speaker 1: place I want to go. It sounds like a place
Speaker 1: where I don't know where you like retreat after you've
Speaker 1: committed a crime. What was the housing development? Unarrested development,
Speaker 1: Sudden Valley or Sudden Yeah? Yeah appropriate as well. So Um,
Speaker 1: like you pointed out, there's an incredible photo essay photo
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 sinkholes open up over some kind of void that
Speaker 1: is formed in the rock below, and as we'll get
Speaker 1: into a lot of that usually has to do with
Speaker 1: water and hydrology. But in this case, the void in
Speaker 1: the rock below the neighborhood was was more was of
Speaker 1: a more artificial persuasion, right. That's because there was an
Speaker 1: abandoned gypsum mine beneath the housing development, and so the
Speaker 1: 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 why
Speaker 1: this tunnel um complex, uh And they encountered the remains
Speaker 1: of what looks like an old like nineteen fifties automobile.
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 mine 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 it's 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 Acred 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 sinots that we see throughout Mesoamerican religion and 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 that you would imagine passages like this appearing
Speaker 1: in you know, Babylonian texts or something. It definitely appears
Speaker 1: in 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 for 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 inspire 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's 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 natural, realistic explanations of this
Speaker 1: kind to explain what somebody thought they saw that appears
Speaker 1: in a story. You know, people are highly imaginative, and
Speaker 1: sometimes stories are just stories. But there's always also the
Speaker 1: possibility that stories like these could be based on people
Speaker 1: hearing stories about having seen I don't know, there was
Speaker 1: a there was a castle or a building or something
Speaker 1: like that that was just swallowed up into the earth,
Speaker 1: which if you didn't have any kind of geological understanding
Speaker 1: with which to to interpret that, it would certainly seem
Speaker 1: to be a you know, a supernatural event. I don't know,
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 sinkholes, and
Speaker 1: we hear stories like this, we see cinematic interpretations. Is
Speaker 1: that idea that the that terra firma is not that firm,
Speaker 1: is not that fixed, that it could change, that the
Speaker 1: that the firm ground beneath our feet could suddenly give way,
Speaker 1: you know, like that alone is just this kind of
Speaker 1: uh you know, horrifying idea. Uh that that it that
Speaker 1: it easily applies as a metaphor to everything else in
Speaker 1: our in our life. You know, that the thing that
Speaker 1: is the order that we depend upon might go away
Speaker 1: at any moment. Yeah, it's interesting to think about like
Speaker 1: a vertical spectrum of of ways that 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, oupening opening up from below, and these
Speaker 1: phenomena intrude on that day to day understanding of physical forces. Yeah,
Speaker 1: so it's it's no surprise We were talking about this
Speaker 1: before the podcast started rolling here that if you start
Speaker 1: looking around for sinkholes online, you'll find just so many galleries,
Speaker 1: top ten lists, lots of click bade about sinkholes. Like
Speaker 1: sinkholes are kind of they're kind of like a like
Speaker 1: they're kind of like true crime. You know, they're um there.
Speaker 1: You also see them, like I was noticing like very
Speaker 1: tabloid sites, sites that otherwise they're not going to really
Speaker 1: have anything related to geology, but they'll have sinkholes. You know,
Speaker 1: it'll be celebrity gossip, um, and you know, maybe some
Speaker 1: conspiracy theories. But then also uh, big old holes opening
Speaker 1: up in the earth. Chump boxes are full of sinkholes.
Speaker 1: Have you ever noticed this? These are the like the
Speaker 1: link um grids at the bottom of blogs and whatnot. Yeah. Yeah, So, like,
Speaker 1: you know, like most websites on the Internet these days
Speaker 1: are just being more and more infected by ads that
Speaker 1: essentially 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 has some
Speaker 1: kind of like health vibe, like it looks like infected
Speaker 1: skin or holes in skin, or some kind of bite
Speaker 1: or something like the kind of a necrotic bite that
Speaker 1: you might imagine someone would get in their worst nightmares
Speaker 1: from a brown recluse, you know that kind of thing.
Speaker 1: Um yeah, they they tie into our like deepest most
Speaker 1: primal fears and desires, just pure eroticism or just pure
Speaker 1: necrotic damage or indeed holes opening up in the earth.
Speaker 1: You know, it's got to be something extreme like that
Speaker 1: to make it into that grid of horror. Yeah, the
Speaker 1: toilet with the rat coming up through it? Remember that one?
Speaker 1: Oh yeah, I think I've seen that one. That was
Speaker 1: a common chumbox image or the like. You know, doctors
Speaker 1: say never eat this vegetable, but they don't tell you
Speaker 1: what it is. Yeah yeah, yeah, sometimes it is um it.
Speaker 1: It's economic as well. You know, there'll be some sort
Speaker 1: generally it's like a picture of an old person and
Speaker 1: just a few like alarming words about you know, investments
Speaker 1: or retirement or something. Right, but that is the world
Speaker 1: will single are actually in their own way. I mean,
Speaker 1: of course, they can be horrifying, they can be destructive
Speaker 1: to human life, but they are also fascinating in their
Speaker 1: own way, in a natural way, they are wonderful. Uh.
Speaker 1: There can be beautiful uh legends and stories attached to them,
Speaker 1: and so I don't know, I feel like they are
Speaker 1: the most uh naturally beautiful thing that that fits in
Speaker 1: the chum box. I mean the rat and the toilet
Speaker 1: can't compete. I mean the rat and the toilet. We
Speaker 1: could do an episode on that as well. But yeah,
Speaker 1: I agree, the sinkholes need to be rescued from the
Speaker 1: chum box. Uh. And that's kind of what we're doing
Speaker 1: in in this episode of stuff to blow your mind
Speaker 1: and the possible second episode to fall. Alright, So sinkholes
Speaker 1: are formed in a number of ways, but most naturally
Speaker 1: occurring sinkholes, like most other things on planet Earth, in
Speaker 1: the end, come back to the power of water. Water,
Speaker 1: of course, is the molecule of life, largely be because
Speaker 1: of its power as a master solvent, and in much
Speaker 1: the same way really that water created life on Earth,
Speaker 1: probably it also creates many of Earth's most astounding geologic features.
Speaker 1: And so this is how we we get sinkholes. For
Speaker 1: the most part so as carbon dioxide in the air
Speaker 1: or in the soil mixes with rainwater, that mixture forms
Speaker 1: a weak acid with the with the chemical formula H
Speaker 1: two c O three. So what you've got there is
Speaker 1: you've got your H two oh the water, and then
Speaker 1: you've got your C O two the carbon dioxide. They react,
Speaker 1: they make a compound with two hydrogens, one carbon and
Speaker 1: three oxygen's And this weak acid formed in the atmosphere
Speaker 1: or in the soil is known as carbonic acid, and
Speaker 1: it is the primary reason that caves exist. Now most
Speaker 1: caves in the world, not all, but most are formed
Speaker 1: by the drainage of acidified water through what you might
Speaker 1: call soluble rock, and uh soluble rock types of rock
Speaker 1: that can react chemically with this water and be dissolved
Speaker 1: and carried away now they're There are multiple kinds of
Speaker 1: soluble rock, including minerals like salt and gypsum, But probably
Speaker 1: the most important, or at least the most charismatic, is limestone,
Speaker 1: which is in itself a fascinating and even mind boggling rock.
Speaker 1: And sometimes I really do think a lot about limestone,
Speaker 1: and maybe people are aren't inclined to be as impressed
Speaker 1: by it as I am. But if you don't believe
Speaker 1: me that limestone is amazing, I think it's worth considering
Speaker 1: that if you live in an area of the world
Speaker 1: you know this primarily resting on limestone, which in the
Speaker 1: United States would include huge portions of like Florida and
Speaker 1: the coastal southeast, big parts of the Midwest. If you
Speaker 1: live in a place like that dominated by this this
Speaker 1: carbonate rock, you are walking around every day on rock
Speaker 1: that is probably mostly built out of dead bodies. Limestone
Speaker 1: can be formed in a number of ways. Some of
Speaker 1: those ways are a biotic, but one of the major
Speaker 1: processes that forms limestone is the gradual deposition of the
Speaker 1: shells and other hard calcium carbonate body parts of animals
Speaker 1: and other tiny organisms in the oceans and rivers and
Speaker 1: lakes where they accumulate on the bottoms of these water
Speaker 1: sources over millions of years, and apparently feces also in general,
Speaker 1: waste products can contribute as well. So the calcium based
Speaker 1: body parts of algae and coral and oysters and all
Speaker 1: kinds of creatures of the sea settle in the deep
Speaker 1: and then they're pressed down and paved over by time
Speaker 1: and pressure until they become layers of sedimentary rock. I
Speaker 1: really just think about that. Sometimes limestone is largely made
Speaker 1: out of life that has died and become rock, like
Speaker 1: the fallen creatures of Earth pile up and become part
Speaker 1: of the crust of the Earth itself. Wow, it's like
Speaker 1: it's like the Medusa's layer, right, just all these the
Speaker 1: petrified bodies. Oh, that's I wish I had thought of
Speaker 1: that when we were doing our Medusa episodes, except I
Speaker 1: guess in the Medusa Garden that they keep their form
Speaker 1: right here. They just sort of like go back to
Speaker 1: whence they came. They become part of this mass. But anyway,
Speaker 1: it's via rocks like this that we get so many
Speaker 1: of the naturally occurring sinkholes on the Earth. So how
Speaker 1: do they form? Well, imagine that there is a storm,
Speaker 1: it rains here in an area with some kind of
Speaker 1: soluble rock, let's say it's a it's a carbonate rock,
Speaker 1: it's like limestone, and rainwater collects on the surface of
Speaker 1: the earth and then runs downhill. And if that rainwater
Speaker 1: drains down into cracks insoluble rock like limestone, things begin
Speaker 1: to happen much in the same way that you can
Speaker 1: dissolve table salt or sugar and a glass of water.
Speaker 1: The crystal contents of these soluble rock surfaces are gradually
Speaker 1: dissolved in and carried away by that acidified water, and
Speaker 1: over tens or hundreds of thousands of years, that dissolution
Speaker 1: of the rock by a water can turn what might
Speaker 1: have started as this tiny stress fracture in a chunk
Speaker 1: of bedrock into an underground cavern large enough for a
Speaker 1: human to climb into. And of course, as the centuries
Speaker 1: go on, these these voids created by the drainage pathways
Speaker 1: of water can just get bigger and bigger. They can
Speaker 1: form underground rivers that form larger and larger voids. And
Speaker 1: it's this dissolution of soluble rock by water that usually
Speaker 1: leads to the creation of sinkholes. Uh though these voids
Speaker 1: in the rock I think sometimes maybe geologists will get
Speaker 1: picky about this. These voids in the rock are not
Speaker 1: technically themselves sinkholes, and we would normally think of them
Speaker 1: as voids or just caves right 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 if you don't mind, I
Speaker 1: just want to share this year. In the fall of nine,
Speaker 1: much of Lake Jackson, a four thousand acre natural body
Speaker 1: of water just north of Tallahassee and a popular site
Speaker 1: for fishing, water skiing, and recreational boating, disappeared down a
Speaker 1: hole like a bathtub, emptying into a drain trophy. Bass
Speaker 1: became stranded in rapidly shrinking eddies, enabling children to catch
Speaker 1: 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 that you know, the the cave beneath
Speaker 1: the lake that is. Yeah, that that that could potentially
Speaker 1: fill back up at any moment. Well. And also, I
Speaker 1: mean I think anybody who, especially people who do like
Speaker 1: scuba diving and stuff, are made uniquely aware of the
Speaker 1: dangers of of being in places that combine water and
Speaker 1: overhead rock. Like, yes, about that that can be an
Speaker 1: specially dangerous and and suddenly dangerous, surprisingly dangerous combination of features. Yeah,
Speaker 1: I mean, even if you are an experienced cave diver,
Speaker 1: cave diving is dangerous. Uh so, um so yeah, that
Speaker 1: is a dangerous realm to to go down into for sure. Now,
Speaker 1: I figured it would be worth talking about a few
Speaker 1: 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.
Speaker 1: S Geological Survey, who has great materials about this um.
Speaker 1: And so the first one is dissolution sinkholes. These are
Speaker 1: relatively gentle sinkholes. You can think of it as a
Speaker 1: kind of top down sinkhole. Here. What you 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 uh, and
Speaker 1: that that overburden pours down fills the void up partially,
Speaker 1: but as it does so, it's sort of like creates
Speaker 1: a depression of visible depression in the surface of the overburden.
Speaker 1: And these types of pits tend to develop pretty gradually
Speaker 1: and 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 that this is the real monster that
Speaker 1: could inspire the geo myth. Potentially, this is the cover
Speaker 1: collapse sinkhole. And these are the ones that can potentially
Speaker 1: happen in an instant and at least in the United States,
Speaker 1: they tend to be most common in places where the
Speaker 1: overburden is mostly clay. So again you start the same
Speaker 1: way that the last one did. Avoid opens up in
Speaker 1: the underlying layer of soluble rock, and then the lower
Speaker 1: levels of the overburden gradually drained down into the cavity
Speaker 1: in the rock. And as this happens, what you get
Speaker 1: is a cavity gradually opening up from from below and
Speaker 1: climbing up into the overburden or the soil itself. So
Speaker 1: imagine again you've got a rock with a cavity or
Speaker 1: a void in it, and then maybe a layer of clay,
Speaker 1: and so the clay on the bottom starts to seep
Speaker 1: down into that cavern below and it just opens up
Speaker 1: a bigger and bigger void in the clay. And eventually
Speaker 1: what's going to happen there is that that void in
Speaker 1: the clay reaches a point where where the collapsing roof
Speaker 1: of the void breaches the surface, which means whatever is
Speaker 1: on the surface falls into the hole. And that surface
Speaker 1: might well be a road or a lake bed, or
Speaker 1: the ground under a building. And this is the example
Speaker 1: where we can see sudden collapses that can be deadly
Speaker 1: and destructive and terrifying because suddenly what you thought was
Speaker 1: solid ground is revealed to have long how to avoid
Speaker 1: beneath it, and suddenly it can't support whatever's 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 sinkholes and potential sinkholes, and in keeping
Speaker 1: track of existing sinkholes that may be expanding, but but
Speaker 1: expanding it may have expanded. But yeah, for the most part,
Speaker 1: like that, the the the idea here is that you
Speaker 1: don't know what's going to happen, and then suddenly there's
Speaker 1: this chasm there in the earth. Now. Another thing that's
Speaker 1: interesting to me about sinkholes is that we often think
Speaker 1: about geological events like earthquakes and volcanoes as what people
Speaker 1: sometimes call acts of God, you know, natural events that
Speaker 1: occur for reasons vastly be on our control and that
Speaker 1: we can do nothing to stop. But there is some
Speaker 1: indication that human activity may have more impact on some
Speaker 1: massive geological events than once thought, and it certainly appears
Speaker 1: to have an effect on the proliferation of sinkholes in particular.
Speaker 1: In other words, sinkhole collapses can it seems absolutely be
Speaker 1: invited by human behavior, as will probably discuss more as
Speaker 1: we go on, but in broad strokes, it appears that
Speaker 1: sinkle collapses can be induced by uh SO, one thing
Speaker 1: is human construction and other changes in the top level terrain,
Speaker 1: especially how that affects water drainage. So you're moving earth
Speaker 1: around and changing the way that water drains on the surface.
Speaker 1: That can lead to sinkhole collapses. But also pumping of
Speaker 1: groundwater is a huge thing here. You pump out groundwater
Speaker 1: from deep underground uh The pressure of the natural water
Speaker 1: that's in the ground helps keep the soil above it
Speaker 1: in place. So if you take that water out, you
Speaker 1: lower the groundwater level, you can cause collapses of the
Speaker 1: overburden lying over now evacuated aquifer voids. Another thing that
Speaker 1: seems kind of relevant to that story you started with.
Speaker 1: Remember the single collapse that turned out to lead to
Speaker 1: a mine down below in South Dakota. The mine was
Speaker 1: a gypsum mine. So gypsum is a major mineral that's
Speaker 1: that's in the ground there. We've been focusing a lot
Speaker 1: on limestone, but one thing to note that I did
Speaker 1: read also from the U. S Geological Survey was that
Speaker 1: other types of underlying rock layers, such as minerals like
Speaker 1: salt and gypsum, those can sometimes dissolve and form voids
Speaker 1: much faster than even sedimentary carbonate rocks like limestone. So
Speaker 1: limestone will form these voids with water running through it
Speaker 1: over you know, thousands of years, but apparently, uh, salt
Speaker 1: and gypsum potentially with the right circumstances can form large
Speaker 1: voids in in a matter of you know, days or months. Well,
Speaker 1: let's get into some examples of sinkholes. Uh. And granted,
Speaker 1: there are so many sinkholes that have either existed for
Speaker 1: you know, thousands of years or have just popped up
Speaker 1: in you know, recent decades. But I want to start
Speaker 1: with one that I imagine is instantly coming to a
Speaker 1: number of your minds. And you're you're especially when we
Speaker 1: were talking earlier about click baity uh sinkholes. And that
Speaker 1: would be the two thousand seven and especially the two
Speaker 1: thousand ten Guatemala City sinkholes. Um, they're they're worth mentioning
Speaker 1: for a couple of reasons. So, so, first of all,
Speaker 1: there are some very dramatic photographs of this thing. Photographs
Speaker 1: so dramatic that they they look photoshopped. You know, they
Speaker 1: don't look real. Absolutely, it looks like something out of
Speaker 1: a movie. Yeah. It looks like a hole has been
Speaker 1: like a cylindrical hole has been bored into this city
Speaker 1: scape and it just descends into absolute darkness. It is.
Speaker 1: It's a terrifying image. Um. And and and when this
Speaker 1: these occurred, I mean, these were dramatic, traumatic events. These
Speaker 1: were deadly occurrences. That two thousand seven sinkhole killed five
Speaker 1: 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 work together to erode uncemented volcanic ash, 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 it just happened, as
Speaker 1: 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's also a good Atlas Obscure article about it, though
Speaker 1: I have to point out that the Atlas Obscura 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 connection to human activities. These were
Speaker 1: caused by oil and gas extraction in the area, especially
Speaker 1: during the heyday of nineteen to nineteen sixty four. UH
Speaker 1: Wink Sinc. Number One opened in nineteen eighty and Wink Sinc.
Speaker 1: Number Two open twenty two years later in two thousand
Speaker 1: and two. And I was looking at a two thousand
Speaker 1: sixteen Southern Methodist University study where they were they were
Speaker 1: taking a look at these sinkholes and the fact that
Speaker 1: they seem to be expanding because the ground there is
Speaker 1: still unstable due to changing groundwater levels and dissolving minerals um. However,
Speaker 1: like I said earlier, were now able to use stuff
Speaker 1: like satellite monitoring to keep a better track of sinkhole
Speaker 1: development and progression. But again this is the case similar
Speaker 1: to what we were describing earlier, where we've taken stuff
Speaker 1: out of the ground and in doing so we have
Speaker 1: disrupted like the you know, the natural balance of things down,
Speaker 1: they're making uh, sinkholes more likely to occur. Looking at
Speaker 1: a picture of the wink sinkholes, uh, just not as
Speaker 1: impressive as some of these because the water level seems
Speaker 1: to have been filled up pretty close to the top.
Speaker 1: So it looks like just a weird pit in the
Speaker 1: middle of the desert that could be like a lake.
Speaker 1: It's just you know, water in it. But uh, but
Speaker 1: I imagine if you that water were to drain out,
Speaker 1: it would look pretty pretty messed up. Yeah. Plus the
Speaker 1: bar is pretty high for spectacular looking sinkholes, as we'll
Speaker 1: continue to see as we discuss other sinkholes in the
Speaker 1: in in this episode in the one to follow. Well,
Speaker 1: so I was wondering, what's the what's the deepest known
Speaker 1: sinkhole on planet Earth? Oh, well, if we want to
Speaker 1: go to the deepest, uh, then we have to go
Speaker 1: to China. That is where we encounter China's um. This
Speaker 1: is the the Shijiao uh Tien King or the Heavenly Pit,
Speaker 1: and it's it's name for a nearby village and then
Speaker 1: uh Tian King just means heavenly pit. And it's located
Speaker 1: near chan Qing in southwest China. It's apparently six hundred
Speaker 1: and twenty six meters or two thousand and fifty four
Speaker 1: ft long. It is five hundred and thirty seven meters
Speaker 1: or a thousand, six hundred sixty two feet wide, and
Speaker 1: it is between five hundred eleven and six hundred and
Speaker 1: sixty two meters deep or between one thousand, six hundred
Speaker 1: and seventy seven to two thousand, one hundred seventy two
Speaker 1: feet deep, So it's deep. That's a big It is
Speaker 1: an enormous hole. And this is one that I recommend
Speaker 1: looking at pictures of because it's is really splendid looking.
Speaker 1: It's beautiful because it um you have the it's it's
Speaker 1: you have this this this double um. It's like a
Speaker 1: double pit. There's like the initial pit and then the
Speaker 1: pit below. You have vertical walls going down to a
Speaker 1: little area that tapers off, and then more vertical walls
Speaker 1: going down even further. There's some rich vegetation around it. Um.
Speaker 1: It's it's really beautiful to look at, and indeed it
Speaker 1: is a tourist attraction if you travel there. There apparently
Speaker 1: two thousand, eight hundred steps constructed that allow visitors to
Speaker 1: journey all the way down to the bottom of that
Speaker 1: second nested pit which I was reading, I think it
Speaker 1: takes you're gonna spend like a couple of hours doing that.
Speaker 1: I think I read that this is also a limestone pit,
Speaker 1: and yeah, one of the great things about it is
Speaker 1: pits of the size and of of this age. You know,
Speaker 1: it's been around for a long time where the surface
Speaker 1: life has just poured down into it, so you know,
Speaker 1: it looks almost like the forest is spilling into the pit,
Speaker 1: and of course the you know, it's a habitat for
Speaker 1: many animals. I think I saw a report that maybe
Speaker 1: rare like the clouded leopard had been spotted there. I think, oh, interesting. Yeah,
Speaker 1: you see time and time again reading about different sink
Speaker 1: calls that they inevitably become uh like an interesting place
Speaker 1: to look at biodiversity. And we'll get we'll get more
Speaker 1: into that later. But yeah, these are these end up
Speaker 1: being you know, they're not just especially ones that have
Speaker 1: been there for a considerable amount of time. They're not
Speaker 1: just holes in the earth. They don't remain voids. Nature
Speaker 1: feels that void and it does so in very remarkable ways.
Speaker 1: Now there are numerous um heavenly pits in this 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 know if you know out there now there
Speaker 1: is another Chinese sinkhole of note that does have some
Speaker 1: cool legend applied to it, and that is a dragon
Speaker 1: hole in the Paracel Islands. It's nine four feet deep
Speaker 1: two hundred and ninety nine meters, so this is out
Speaker 1: in the ocean. It's also known as the Young Lu
Speaker 1: dragon Hole, named for the fifteenth century Mean Dynasty Young
Speaker 1: Lu Emperor Um. It's also known as the Eye of
Speaker 1: the South China Sea and the tradition here is that
Speaker 1: this is where the Monkey King uh soon Will Kong
Speaker 1: finds his golden cudgel in Journey to the West. So
Speaker 1: this would be his magical staff. If you've ever seen
Speaker 1: a movie with the with the Monkey King in it,
Speaker 1: or seeing images of the Monkey King, this is his big,
Speaker 1: amazing fighting staff. So he actually gets it from this pit.
Speaker 1: Well that is that is what they've sort of taken
Speaker 1: the 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 Ao 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 gray It's measuring stick for determining the
Speaker 1: depth of the Great Flood, So it has that would
Speaker 1: make sense that you know, it would be underwater because
Speaker 1: there's this connection to the depths, and so anyway he
Speaker 1: dives 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: is in Belize. Um. So the way that looks from
Speaker 1: above is that, yeah, you'll see a sort of just
Speaker 1: ring of dark blue surrounded by much lighter blue as
Speaker 1: as I guess, that just reflects the sudden difference in depth. Yeah, exactly,
Speaker 1: it's this is very much in keeping with the Great
Speaker 1: Blue Hole, just maybe less dramatic looking, but still extremely beautiful. Now.
Speaker 1: In is reported by Danny Lewis for Smithsonian mag dot com,
Speaker 1: researchers discovered uh like something like forty nine sinkholes clustered
Speaker 1: close together while serving the chin Lang Bashan Mountains in
Speaker 1: China's uh uh Shaanxi Province, the largest being one thousand,
Speaker 1: seven hundred and six ft or five hundred and nineteen
Speaker 1: meters wide and a thousand and fifty or three hundred
Speaker 1: and twenty feet deep. So um, yeah, it's uh. We
Speaker 1: keep finding these things, you know, or in many cases,
Speaker 1: rediscovering them, and every time discoveries like this, you're made.
Speaker 1: You know, it's not just an interesting geologic curio, it's
Speaker 1: a fresh opportunity to gaze back in time to understand geology, biology,
Speaker 1: and even the climate of the region in in times past.
Speaker 1: Oh yeah, because this is an interesting thing. You were
Speaker 1: pointing out when we started looking at this, that sinkholes
Speaker 1: are often used as a kind of scientific time capsule,
Speaker 1: that there are ways that sinkholes can tell us things
Speaker 1: about the past the face 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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