SciShow Tangents - Deserts

Episode Date: August 6, 2019

You might think you know everything there is to know about deserts: big, sandy, hot, etc. But between the alien mummies and the ice blades, we're guessing there's a lot you don't know. All that and you get to see Hank just totally embarrass himself while trying to talk about Pokemon. Follow us on Twitter @SciShowTangents, where we’ll tweet out topics for upcoming episodes and you can ask the science couch questions! If you want to learn more about any of our main topics, check out these links:[Truth or Fail]Atacama Desert:Ata:https://www.nytimes.com/2018/03/22/science/ata-mummy-alien-chile.htmlhttps://www.smithsonianmag.com/smart-news/tiny-alien-skeleton-found-chile-was-likely-result-genetic-mutations-180968576/Ice Blades: https://www.sciencealert.com/eerie-ice-spires-harbour-life-in-one-of-the-harshest-environments-on-earthMicrobes:https://www.nature.com/articles/s41598-018-35051-whttps://earthsky.org/earth/mars-like-atacanda-desert-rain-brings-death[Fact Off]Thorny devil lizard:https://royalsocietypublishing.org/doi/full/10.1098/rsos.170591Libyan Desert glass:http://news.bbc.co.uk/2/hi/science/nature/5196362.stmhttps://www.sciencedirect.com/science/article/pii/0022309384901777https://pubs.geoscienceworld.org/gsa/geology/article-abstract/47/7/609/570318/overestimation-of-threat-from-100-mt-class?redirectedFrom=fulltexthttps://theconversation.com/how-we-solved-the-mystery-of-libyan-desert-glass-117253[Ask the Science Couch]Sand depth:https://link.springer.com/referenceworkentry/10.1007%2F978-1-4614-9213-9_325-1https://link.springer.com/chapter/10.1007/978-3-319-65661-8_10https://earthobservatory.nasa.gov/images/92232/grand-erg-oriental-algeriahttps://www.nps.gov/zion/learn/nature/sand-dunes-sandstone.htm[Butt One More Thing]Dung beetles:https://www.eurekalert.org/pub_releases/2012-10/uotw-bud101912.phphttps://www.cell.com/current-biology/abstract/S0960-9822%2812%2901061-5 

Hello and welcome to SciShow Tangents, a lightly competitive knowledge showcase starring some of the geniuses that make the YouTube series SciShow happen. This week, as always, I am joined by Stephen G. Hello. Hi. Do I sound different? You sound about the same. Are you not feeling the same?

No, we're coming back from VidCon. Right. After VidCon, everything's changed. Thousands of children coughing all over me all weekend. What's your tagline? Leaky nose holes. Sorry about that. Stay over there.

Sam Schultz is also here. Hello. Sorry you have to spend all this time next to Stefan. Oh, that's okay. I think I'm probably also sick, but I'm still, you know, stronger. What's your tagline? No juice. No juice.

Whoa. We're low on juice. Sari, how are you doing after VidCon? I'm okay, but now I'm worried because I sat next to Sam and Stefan on the plane. Are you weak or strong? I don't know. I think I'm strong, but probably just mentally, and then I'm going to collapse in a couple days. What's your tagline?

Vegetable on Wii. And I'm Hank Green. I have no more space in my whole head. It all filled up. You need more gigabytes or whatever. I need some more space in my whole head. It all filled up. You need to have more gigabytes or whatever. I need some more gigabytes. Somewhere around or something. I need an expansion drive.

External hard drive just like. Plug it in your butt. Plug it in my butt. And my tagline is hot, hot MSG water. Every week here on SciShow Tangents, we get together to try to one up a maze and delight each other with science facts. We're playing for glory and we're also playing for Hank Bucks. We do everything we can to stay on topic, but if you go off on a tangent and we all deem it unnecessary or unworthy,

we will dock you one of your Hank Bucks. We'll even make you go negative. Now, as always, we introduce this week's science topic with a traditional science poem. It's from me. We introduce this week's science topic with a traditional science poem. It's from me. How do we rise and bloom? How do we survive? How do we respirate, photosynthesize, and thrive? This poem is from the perspective of plants.

How do we retain the water even though there is no trace? We must capture everything we can and store it just in case. This land is not of plenty, but we're built to endure. If it's possible, we'll do it. Of that you can be sure. We can last, but not forever. So we say to this terrain, give us that precipitation, give us that rain. It's a good poem when it has to have a parenthetical in the middle. I meant to say it at the beginning.

That was much better there. The topic of the day is deserts. All right, Sari, what's a desert? That was much better there. The topic of the day is deserts. All right, Sari, what's a desert? It seems like most scientists define deserts as areas that have an annual precipitation of less than 250 millimeters per year. And so that's like 10 inches.

So there's just like a scientific cutoff. Here in Missoula, we have 350 millimeters of rain a year. So we're pretty close. We just squeaked right in there. It's pretty dry here. Yeah, so it's just like very little water falling. So it's really that. That's the thing. It's the amount of water.

Because you hear like Antarctica is a desert. You don't think it's like water, water everywhere, right? Yeah. It's just icy. It's just icy. Yeah, it's all trapped within the ice. There are different types of deserts. Subtropical deserts have to do with air circulation.

The Sahara Desert is a subtropical desert. So like wind makes it hot. Coastal deserts are where air blowing towards shore produces fog, but not rain. So it's like doesn't create precipitation, even though it might be humid. It's just rainless. And then that's considered a desert. So like the Atacama Desert on the shores of Chile is a coastal desert. I know a thing or two about the Atacama. Do you? What? I do.

We'll find out. Rain shadow deserts are like behind a mountain. That's what we're in. Yeah. Death Valley is one of those too. Wait, so we're in a desert right now? We're not. But that's why we have a little precipitation because we're in a rain shadow.

Yeah. Rain shadow effect happens anywhere there are mountains around. Just like more rain on one side, less rain on the other. Idaho's all wet. It gets all of our wet. And then we're over here being like, my nose is bleeding. What's the deal with all the sand? Where is that coming from?

Not all deserts have sand. So sand happens, as far as I can tell, geologists might have more information than this, but when the nutrient-rich topsoil goes away, then what's left is like rocky chunks, and then that's sand, and they just get eroded down into smaller and smaller bits. Okay. Sand is the absence of dirt, basically.

Right. Sand is just like dry, bad dirt. And it's heavy, too, so it'll like stick around. It's it'll like stick around that doesn't get blown away yeah that makes sense there's no like vegetative parts to sand the way it is to soil a lot of soil is like decomposing stuff yeah a lot of sand is quartz based so it's like uh silica tiny rocks according to research or like media speculation i don't know how much is what because I didn't read extensively. The world is running out of sand now that we have uses for sand. And even just probably moving it around for construction sites. I don't know.

It's like I have good weight for things. And people are like, ah, sand's free. Grab it. But it just takes so long to make. And now that humans are moving it from place to place, we have a problem. Snag some of those sandy asteroids. I mean, it does seem like you can make sand.

You just gotta take some rocks and hit them against each other. Whack some rocks. And now it's time for Truth or Fail. One of our panelists has prepared three science facts for our education and enjoyment, but only one of those facts is real. The rest of us have to guess or determine through what we already know which one is the real fact.

If we get it right, we get a Hank Buck. If we don't, Sam gets it. And then maybe in that case, I will no longer be tied anymore. Yeah, then you're screwed. So the Atacama Desert, which we talked about earlier, is in Chile and it's one of the driest places in the world. I wrote this before I knew the definition of a desert. But the next sentence is generally receiving just a few millimeters of rain every year. That's very dry.

Obviously. It has to. So it's so dry that it shares a lot of similarities with Mars and is often used as a Mars stand-in to test Mars-bound rovers, tools, and experiments. stand-in to test Mars-bound rovers, tools, and experiments. However, in 2015 and again in 2017, the desert experienced its first significant rainfall in as much as 500 years. Whoa. And that led to a very unexpected outcome. So, what happened when it rained in the Atacama Desert?

Ooh. Can I make a guess? No. Wait, yeah. Okay. Well, no, if you say something and it's one of the answers. Yeah, don't say it. One.

Thin, blade-like ice formations, some as tall as 16 feet, formed in the cold desert night. Two. The rain killed 80% of native microbial life. Three. The rain unearthed a tiny, mysterious skeleton thought by some to be an alien. Blades of ice 16 what's tall rmt again thin blade-like ice formation some as tall as 16 feet formed in the cold desert night the rain killed 80 of native microbial life or the rain unearthed a tiny mysterious skeleton that some people thought was an alien i mean the most believable thing is that some people thought was an alien. I mean, the most believable thing

is that some people thought something was an alien. Because every time something is unearthed... It could be an alien. It's an easy first thing to guess. Yeah, I don't recognize this, so it must be an alien. Yeah, someday we'll be right. Probably not on Earth. We probably won't find a thing on Earth and then...

I feel like this is a dangerous line of inquiry to head down. It seems like a tangent waiting to happen. Are we going to talk about whether aliens have showed up here? Because that seems like a bad idea. We won't talk about aliens. By now, those people have stormed Area 51 and will know if they're real or not. I feel like I would have seen pictures of thin, blade-like ice 16 16 feet tall sam's very good at finding things that we should have seen though true should have in quotes true did anyone fight with them like

like two people grabbed each grabbed a blade maybe at some point in prehistory some kind of giant blade 500 years ago last time it happened yeah well i imagine that the blades are very thin like needle ice or something because Because I'm imagining this. What's needle ice, Sari? Is that a thing? Yeah, I think it is. I don't know. I can't Google it to make sure.

This is like the back of the brain. That's not where knowledge is stored anyway. That's where the old stuff is. Deep in the brain hole, dusting it off. There's some sort of like frost flower needle ice they're all ice made from ice being extruded out of wood or soil or something so it like freezes and then expands and then like poops out a little shape yeah and so i could see something like water soaking into the ground and then being squeezed out through the holes in between the sand right and then like

the bad guy holds you over it as it slowly grows into your chest. Do deserts get colder than other places at night? Deserts do get cold, yeah, for sure. Because less water in the air means that it holds on to less heat. And Chile's cold. Yeah, it seems like a cold country. Ice blades. Sounds real to me.

Stefan likes ice blades. We haven't talked at all about native microbial life. This one seems by far the least interesting, which makes Sounds real to me. Stefan likes iceblades. We haven't talked at all about native microbial life. This one seems by far the least interesting, which makes it appealing to me. Oh. Microbes are hardy, though. It's true. But they're hardy in the circumstances they're designed for or they evolved for. Which is watery.

This would be a whole new one. No, because these ones are desert microbes. Yeah. I agree with Hank. I think they're desert. I think they're dry microbes. And they got wet and they couldn't breathe.

They're like, I'm drowning! I'm drowning! Oh, it's like when you leave your cornflakes in milk for too long. Yeah.

I'm going with number two. That rain killed all those microbes. Also the same. You know what? I'll go with the alien. What? Let's do it. Ooh, go with the alien. It's totally switched. No more ice same. You know what? I'll go with the alien. What? Let's do it. Go with the alien.

It's totally switched. No more ice blades. You know what, guys? That water killed all those microbes. No. Yes! The rain happened, and the scientists went out. They thought that there would be, like, an explosion of life. They took a sample. They had previously

known about 16 varieties of microbes that lived in this dirt. They only found four varieties. And it killed like completely all the other varieties of microbes from something that they called osmotic shock, which I guess is microbes having too much water. Is that what it is? The balance of water being bad for them. Yeah, it just like popped them.

Probably because like it might be a salt thing too. There might be like a lot of salt inside of them when they have fresh water on them and it like sucked all the water out of their insides popping them or pulled all the water into them and popped them right that's water into them oh man so since they study it like they study mars some scientists think that this event should help should like recontextualize how we look for life on Mars because there are very similar chemical properties to the dirt there that there are on Mars with lots of nitrates from previous bodies of water, they think. And the microbes live in that area. So when the Viking lander went, it was researching in those areas

and it was trying to cultivate Martian bacteria by putting water on them but they think that it's possible that by putting water on it on mars they just killed all the microbes that could have potentially been there so there might be a better way to go do it that isn't just put water on everything uh so the other two are also things that were found in the Atacama Desert. Exactly. So. Aliens. Ice blades are colloquially called penitent snow because they look like, if you see them, they look like a bunch of praying priests, like kneeling sort of is what the thought is. And there's snow formations that grow in the Andes,

which is adjacent to the Atacama Desert. I think they must be blades because the wind might whip through them. Right. So like snow comes and then like the wind goes through and erodes the snow. Yeah. But they grow in super high and super dry places. And they're really, really hard to get to.

But I think last year there was some researchers who went up there and found some of that pink snow bacteria, that pink snow fungus or whatever it is growing on them and they said something about how that meant there could be life on mars too they're always looking for life on mars things in the atacama desert and the last one is the tiny skeleton the skeleton was found in a ghost town and these i guess it was just like on display somewhere and a rich person bought it brought it to america i think and did some dna testing on it to see what it really was and it turned out to be a human fetus that was about 40 years old and it had the skeletal structure of like a four-year-old child but it was a fetus wild i'm looking at a picture of it i think it looks like an for sure. But it was just like a mummified fetus that had some kind of...

Abnormality? Yeah, that made it extra bony. Yeah, I mean, if you showed me that thing, if I was like walking through the desert and I saw that, I'd be like, oh. Really scared. Well, I have found an alien. Yeah. And I need to call someone important to come look at this alien for me. And I'm a fairly skeptical person, but that's definitely an alien-looking thing.

When I first saw it, I was like, there's no way that's not fake. But you're telling me that it's actually a human DNA? I mean, there were like Eureka Alert papers about them finding DNA that corresponded to a lot of different birth defects and stuff that you can still find today. All right, well, now you guys know everything about the Atacama Desert. More importantly, we didn't get fooled by your lies. Yeah, I like the ice blades, though. They're really pretty. I want to look at pictures of them.

We'll put them up on the... Yeah, they look really cool. SciShowTangents.org. Next up, we're going to take a short break, and then the fact off. Welcome back, everybody. Hank Buck totals. Sarah's got one. Stefan's got nothing. And I've got two.

So I'm still tied with you. Because you got one. Yes. That's right. Now it's time for the fact off. Two of our panelists have brought in science facts to present to the others in an attempt to blow our minds. We each have a Hank Buck to award to the fact that we like the most.

It's Stefan versus Sherry. We're going to go by who most recently had a drink of water. Oh, I've been drinking water all pod. Yeah, I drank before, but I left my water bottle upstairs. All right, Stefan goes first. I'm so hydrated. I'm always worried I'll have to pee halfway through. I do have to pee.

Let's go. In the desert of Australia, there is a species called Molok horridus, and it's called the thorny devil. And it's a super thorny lizard. And it looks super cool because it's like completely covered in these like thorns that look very much like plant thorns to me, like a rosebush thorns or something. And it holds its tail in the air, which is kind of cute. Stefan, for his fact, found a cute thorny lizard.

That's it. Look how cute. So skin is super thorny and super rough, but hidden in that roughness is kind of another feature that helps it survive in the desert. And so it basically has these ridges or grooves in its skin along its entire body. And if water ends up on its body anywhere, it gets drawn through the grooves,

through capillary action, straight to its mouth. Oh. What the heck? And so it can just be like... Oh, that's great. Just stand in there, and water gets drawn straight to its mouth. Its whole body is like one of those hats

that have straws coming down. It's like a still suit, but on the outside. I was thinking about, would I want this ability? But no, because as soon as you start in like a muddy puddle yeah or like oh your body's not super clean all your butt water gets funneled up to your mouth it's like no no you gotta keep your butt very dry yeah yeah never use a bidet no it was squirt white in there. During the morning, it brushes up against grass and, like,

tries to get dew to fall on it. I assume, like, having the rough skin in the thorns helps with this, but, like, water will condense

on its body overnight and it can drink from that and if it rains, it can just suck up water from anywhere on its body. So that's my fact. I love it. Oh, I love it, too.

What do you got? I don't have anything nearly as cute. That's not what. I love it. Oh, I love it, too. What do you got? I don't have anything nearly as cute. That's not what it's about. It's not about cute, Sari. It's about science. Mind-blowing facts. In the center of one of King Tut's pectoral jewelry pieces, there's a scarab made from unusual yellow-green glass.

It's called Libyan desert glass, and it's estimated to be between 28 and 29 million years old. Whoa. And this is actually just one of hundreds of fragments of this glass that's scattered across the Sahara Desert near the border of Libya and Egypt, which is sort of weird. And chemically, glass is an amorphous solid. This is like my parenthetical in the middle of this fact.

It's formed when a compound like silica, which is a big part of sand like we talked about earlier it gets melted into a liquid and then cooled really rapidly so no crystalline structure can reform instead of a crystal it's just kind of globby in there and that means that the sand in this portion of the desert had to get really hot like temperatures above 1600 celsius at some point and how that happened i know how it happened there was a giant space magnifying glass yeah the aliens they just had a magnifying glass and then they dropped it and then it shattered and then that's the glass they didn't use it to heat up the thing they just dropped their giant space magnifying glass yeah they're like dang it but how it actually happened is kind of a mystery.

There are two main hypotheses. One, there was an explosion in the atmosphere called an airburst, which is like an asteroid or other object burning up and releasing a lot of heat. The estimated strength to cause this much glass is 100 megatons, which is a unit usually used for nuclear weapons. So one megaton is one million tons of TNT. This much glass is 100 megatons, which is a unit usually used for nuclear weapons. So one megaton is one million tons of TNT. The nuclear bomb dropped on Hiroshima was 15 kilotons.

So this is hypothetically like 6,667 times that worth of explosion. Is that like what happened in Russia with the meteor? That was like a 50 megaton, I think. So that's one hypothesis. The second hypothesis is a meteor that crashed into the desert, created an impact crater and melted a bunch of sand. And that's all now covered in sand or something, so we can't see it? Yeah. And so as of now, scientists are leaning towards the second one, like the meteor impact, because they found evidence of a mineral called, I think it's pronounced redite, in some glass fragments, which only forms during meteorite impacts.

And I couldn't find an exact reason why, but I think pressure makes sense. So like you need the heat plus the boom of the pressure. And then it reverts into zircon, which is a mineral that's found in a lot of rocks and we use to date old things. But even with that evidence of this one particular mineral in this glass we have lots of questions like where is the crater how big is it because we haven't found any edges of it or transition zones that you would normally be able to see and scientists just have no idea they're like this is a giant mystery we know this glass exists we

know a lot of it exists but we don't know know. It's also spread all over the place, which is wild. So over the millions of years of geologic time, which isn't that long. It's long for humans, but not in the grand scheme of the earth. In a non-desert environment, you'd have that stuff being transported by water, and you'd lose a lot of that. It'd get buried really quick. But one of the nice things about deserts is that actually allows for things to stick around for a long time which is why antarctica is such a great place to find meteorites there's very little precipitation so they just sit there on the surface of the ice so you can just go find them cool it's since it's only in that one place does that mean that it's only from one event ever in

the history of earth that has ever happened this is one event however many million years ago and there are other places in the world where glass has been formed from explosions so like during the nuclear test in the united states there's a type of glass that was formed is there other stuff made of that other jewelry and stuff made of that um i think there are there's evidence of tools made from it so kind of like how people used obsidian as tools. But I think you can buy it online. So that means there's some. That's only $36 on

Etsy. It says rare Libby and glass meteorite impact glass. It's $36 so it's not that rare? I'm just going to put it out there. King Tut would be embarrassed if he knew he was buried in something that only cost $36. Yeah.

He had a lot of gold on there, too. It was like a very fancy... I don't know why they didn't call it a breastplate. It was just like pectoral jewelry. Well, yeah. When you said that, I was like, what does that mean? Like, I've never seen... In modern times, I've never seen anything that I would say, oh, pectoral jewelry. It's a nipple, right?

Nipple clips, yeah. Oh, yes. Okay. We got lots of visual aids. Go to scishowtandards.org to see all like weird lizards, good pectoral jewelry, some Pokemon. Sure, I'll throw a couple Pokemon. Just a surprise in there.

I'll link to Bulbapedia. There's desert Pokemon, right? There's a camel, I think. Yeah. Probably. Scrafty. Yeah, I guess. There's also cactuses.

Oh, okay. More Pokemon. Yeah. No, I was just excited we were talking about Pokemon because I know these things. You say you know, but there's like 30 of them you guys haven't said. Trapinch. There's Johto, Hoenn, Sinnoh, Nova, Kalos, Alola. Those are the countries Pokemon live in.

What the hell I typed in desert Pokemon And that's what it told me So we've got ancient Mysterious desert glass Versus butt bidet Water siphoning Thorn lizard Very hard

Both of those are good I'm going to give my point to the lizard that can drink its own butt water. I like that. I'm also going to go with the thorn lizard. Sorry, Sari. That's okay. It's so cute and cool. It could be a Pokemon.

Thornizard. His move is butt water. I feel like Thornizard is better than Buttwaterizard. It's only one Pokemon that ends with a zard. But it's a lizard. Yeah, I guess so. Even though Charizard appears to not be a lizard. He's a Wovern.

Charizard has hands. Yeah, Woverns have two legs and little arms. No, dragons have arms and wings. Wivrens have no front arms. Don't dragons walk on all fours, though? Yeah. Not Charizard. Well, they don Don't dragons walk on all fours, though? Yeah. Not Charizard. Well, they don't have to walk on all fours.

They just have... Wyverns only have four limbs. Dragons have six. Oh, okay. He does have six. I think we need to... I think we should back up on that. He's an insect, too.

Oh, yeah. Sam for bringing up the Wyvern thing. Yeah, this was not the place for Wyvern discussions. That's fine. We had a whole episode on dragons. Yeah. Why didn't we lose a point when we were talking about Pokemon earlier?

I almost did it, but then it came back again. All right. So I guess now it's time to ask the science couch. We've got some listener questions for our couch of finely honed scientific minds. And this is going to be read for us by Sam. At the Canadian Giant asks, how deep can sand get in the desert? How deep can sand get in the desert? How deep can sand get? All the way down.

Oh, boy. Well, I bet there's a certain point at which the sand compresses itself and it no longer becomes sandstone. But not into glass. No, not into glass. Because you need heat. Because that would be amazing. We really just live on a glass orb. Surprise.

Surprise. We live on glass, Paul. How deep would it get? I don't know. Sarah worked so hard to try and figure out the answer to this question. And I think that we don't know. They say that we're running out of sand, but no one's ever tried to dig to the bottom of the desert.

Yep. And no scientist cares. No scientist has ever gone out to the desert with a shovel and been like, well, let's start digging and see how deep this baby goes it seems like the kind of question that people like me would be like oh important science yeah and scientists are like who cares it doesn't matter so i did learn a new word an erg erg is what they call like any sort of sandy desert. It's also a dune sea or a sand sheet, I think are all variations on this. But it's basically like a big desert area that contains sand that gets blown around by wind. And they can form big dunes or just be flat layers. And so I think they can extend

anywhere from like a meter deep and then bedrock is right beneath it. So it's just like a very thin layer of sand to, I don't know, really tall dunes. So those are hundreds of meters high down to sandstone or bedrock or whatever's beneath it. But it seems like scientists are more interested in how sand moves. So I don't know, we've studied, for example, singing sand. That's when sand gets blown across it and creates sounds. And so scientists are interested in that phenomenon. That sounds very cool. So, yeah, so scientists are more interested in questions about sand as like an ecosystem, like how plants interact with sand or animals interact with sand or how sand interacts with itself and moves around,

how wind interacts with sand and moves around, how wind interacts with sand and causes different formations or erosion. And no one's just measuring how deep it is. There's also some indication that in previous times we've had far deeper dunes than we have now based on sandstone deposits. Yeah, I was reading about that too. So in Utah, the Arches National Park, for example, is known for its big sandstone formations full of layered rock and all that had to be sand. Covered in sand at one point. At some point, yeah, and be compressed.

And so all of that was once sand at some point before it was sandstone. And now it is once again returning to sand. I feel like I ignored geology for a really long time because I was there was some like piece of me that had placed it into like the less interesting science category. And I deeply regret it now. I feel like when you live in Montana, like when you grew up in Montana, you look at the sides of rocks like dug into the highway or like the mountains or huge weird boulders just in the middle of the like prairie for no reason. So I don't know anything about any of it but i think about it a lot you think about it all the time cool rock yeah

i grew up in florida where there's no rock everything's just yeah wet swampy you got river rocks you got other kind of rocks no no river rocks in florida yeah here the bottom of the river is like beautiful clean rock in florida bottom of the river is just like soft alligators. And a snake. A snake coming out to get you. Is the desert still spreading? Because I remember when I was younger, people talked about that all the time. Oh, like the desert was expanding and cutting down stuff and there was desert encroachment?

I remember that, too. I did read a little bit about desertification. So that is a word to describe when you take like fertile land and it becomes a desert. So I don't know how that happens exactly. This is an agricultural science question. Hank might know more, but there's soil on top,

like kind of like what we were talking about with how deserts form in the first place, like soil is nutrient rich. And then if you sap all the nutrients out of that by replanting the same crop in the same place over and over and over again you suck it all dry sand and then it becomes more sand like right that's a problem is overusing soil until it becomes more desert like and i'm guessing that the encroachment thing is just human civilization we built cities and

like the sand moves around and the sand blows. And so I can imagine people clearing out a space, building buildings, and then the sand just naturally progressing. If you want to ask the Science Couch your questions, follow us on Twitter at SciShowTangents. We will tweet out topics for new upcoming episodes. Thank you at MisplacedVulcan,

at LilVonWink, and everybody else who tweeted us your questions. Final scores! Sarah, you got one. I got two. Sam, because you made too many Pokemon references, you have zero points. And Stefan ties me with two. You're winning now, officially.

I'm officially winning. Take that. Shouldn't talk about Pokemon so much. Congratulations. How about that? I appreciate you appreciating me. Take that. Congratulations. How about that? I appreciate you appreciating me. Take that. Wow.

If you liked this episode and you want to help us out, it's easy to do that. You can leave us a review wherever you listen. Helps us know what you like about the show and it shows people,

other people who might be interested in listening to it, more data about what the show is like. Also, we will be looking there for ideas for future episodes if you want to leave topic ideas. Second, tweet out your favorite moment from this episode so that I can like that tweet

and also remember, ha, that was fun with my friends. That was great. And finally, if you want to show your love for SciShow Tangents, you can just tell people about us. If you want to read more about any of the topics today, you can check out SciShowTangents.org to find links to our sources.

Thank you for joining us. I have been Hank Green. I've been Sari Reilly. I've been Stefan Chin. I've been Sam Schultz. SciShowTangents.org to find links to our sources. Thank you for joining us. I have been Hank Green. I've been Sari Reilly. I've been Stefan Schinn. I've been Sam Schultz. SciShow Tangents is a co-production of Complexly and the awesome team at WNYC Studios. It's created by all of us and produced by Caitlin Hoffmeister and Sam Schultz, who also edits a lot of these episodes, along with Hiroko Matsushima. Our sound design is by Joseph Tuna-Medish.

Our social media organizer is Victoria Bongiorno. And we couldn't make any of this without our patrons on Patreon. Thank you. And remember, the mind is not a vessel to be filled, but a fire to be lighted. But one more thing. Dung beetles are known for rolling balls of poop around,

and the ones that live in the desert have to step all over hot sand. So researchers experimented with one South African species and noticed that when the ground is hotter than 50 degrees Celsius, 122 degrees Fahrenheit, they hop up on their poop balls and preen their legs to cool down. Oh, yeah. I do that on the beach sometimes when I get real hot.

A poop raft? You hop up on your poop ball? No, I just lick my feet. Oh, whoa! You are just foul.