From the Vault: Mud, Part 1

Published Jul 20, 2024, 10:00 AM

What exactly is mud? Where does it occur and how does it factor into animal behaviors and human activities? In this classic four-part Stuff to Blow Your Mind exploration, Rob and Joe immerse themselves in the mysteries of mud. (originally published 07/06/2023)

Hey, welcome to Stuff to Blow Your Mind. My name is Robert Lamb. It's Saturday. We're venturing back into the vault. This is going to be part one of our let's see, this was a four part series that we did on mud. You know, if you listened recently, you may have heard our series on dust. Well, similar we're talking about mud and there so we get into all sorts of different angles here in these four episodes. So it might seem mundane on the surface, but once you sync into it, I think you'll find it as fascinating as we did. This episode originally published on seven six, twenty twenty three. Here we go.

Welcome to Stuff to Blow Your Mind, a production of iHeartRadio.

Hey, welcome to Stuff to Blow your Mind. My name is Robert.

Lamb, and I am Joe McCormack. And today we are going to be starting a series of episodes on mud, a topic that I promise is more interesting than you might think. And to get us started today, I wanted to talk about a section from an English epic poem that endorses the belief that mud just happens to give rise to monsters or monstrous creatures of various shapes. So the poem in question is a late sixteenth century epic poem by the English poet Edmund Spencer called The Fairy Queen. I took a class in college where we read this, or we read part of it. To be honest, there's a lot that I forget about it. But it's very much your classic epic poem, with heroic knights, the Red Cross Knight, and damsels in distress and witches and ogres and all that. And there's an interesting passage toward the beginning of The Fairy Queen. I think it's in book one, Canto one, where Spencer implies a belief about the way nature works, a belief that the mud, specifically the mud of the Nie River, spawns monsters, and Spencer writes quote as when old father Nilus gins to swell with timely pride above the Egyptian veil, his fatty waves do fertile slime out well and overflow each plane and lowly dale. But when his later spring gins to a veil, huge heaps of mud he leaves wherein their breed ten thousand kinds of creatures, partly male and partly female, of his fruitful seed, such ugly, monstrous shapes elsewhere may no man read. And then Spencer later cites the same belief again as a kind of illustration of a general principle. He writes, but reason teacheth that the fruitful seeds of all things living through impression of the sunbeams in moist complexion, do life conceive and quickened are by kind. So after Nilus inundation, infinite shapes of creatures men do find inform in the mud on which the sun hath shined. So I think he seems to be saying like mud plus sunshine equals monsters, or at least creatures of infinite shapes, which in some passages he seems to think might be monsters. Maybe among infinite variation there will necessarily be some monsters. And I'm interested in this belief because, on one hand, it just sort of reflects some ancient beliefs that are carried over into the Medieval and Renaissance period about where life comes from, ideas now obsolete theories like spontaneous generation that you know that life forms, which is sort of like arise in the mud or in like a wet bag of flower or something. But I also like it because it imagines the mud in the floodplain of a great river like the Nile as a source of both like sort of mystery and danger but also great possibility. And this does correspond to the kind of the double nature of mud and of a river like the Nile. So you think of the Nile River delta, it is a place of incredibly fertile soil that you know, that supplies food and crops for all of the areas around. But also if you know, you get stuck in the mud, that's a place you don't want to be. And it is a place where you will find lots of life that is maybe life that's kind of strange to you. You don't usually go wading into the mud, and if you do, I don't know, all kinds of weird little mollusks and creepy crawleys and critters are in there, and you don't know what you might find.

Yeah, yeah, this is really interesting. We should also note, you know, it does accurately, though monstrously refer to the the the inundation of the Nile, which is a topic we did an entire episode at least one episode on in the past. I mean, the Nile overflows its banks and it brings life and has this this very prominent role in especially in ancient Egyptian belief and mythology. But yeah, this dual nature of mud is quite interesting and something that that we're going to be talking about quite a bit in these episodes because it at once it is like you want to build something, well, you're gonna need something like mud or mud itself. But of course it's also the place where you know, many a famous military campaign has perished in the mud, so you know, it's the thing from which monsters emerge, but it's all you know, it's the thing where you might find a pig, but you also will find gleaming butterflies, you know, cascading and swirling around something some stinking pile of mud. So yeah, it does seem to have this dual nature, at least from the human vantage point.

So our goal is after we're done with this series, you will never think about mud the same way. And when it gets stuck to your shoes, you might still be mad, but there will also be a part of you that that's kind of reflective and stops to be amazed at what it is. Your dog has just gotten all over your couch.

Yeah, and if you're like me too. Just even thinking about this topic, it means that you've had the Primus song my Name is Mud just flipped on in your brain. I haven't even listened to it to encourage or extinguish it, but it's just there as I read these various papers about mud or mummama mud, Right, I guess that's the way.

It's said, and so I'll take your word for it.

It's a solid jam. It's got some colossal bass and drums on there.

Oh yeah, that's primus. They rattle the furniture. But anyway, we should go straight to the question what is mud? What is it made of? In general, mud seems to have a kind of loose definition. We all know it when we see it, but there may not be strict scientific criteria about what counts, except maybe in certain contexts, like when you're talking when you get to some things we'll get to in a minute about like particle size and what solidifies into certain kinds of rock. But just generally, I mean, mud is some sort of wet soil, but exactly how wet, Exactly what are the properties of the soil for it to count as mud versus just being kind of like I don't know, damp, gross stuff that might be in the eye of the beholder, of the beat or of the bee treader.

Yeah, I would. I would. I think that sometimes we know it when we see it, but we definitely know it when we step on it or step in it. I guess that's the thing, right. If I'm able to step on it, well maybe it's not fully mud. But if I'm in it, well I am in mud now. But I think the other Yeah. The other interesting thing about mud is a lot of it does depend on where you're coming from, you know, like if you were a domesticated hog, well, mud is just simply good. There's not much else to say about that, though. We will get into how various animals use mud later on in a subsequent episode, but just from the human perspective, it's kind of interesting. One of the books I was looking at, and we'll come back to later when we get more in depth on this is a book titled Mud, a Military History by ce Wood, which, if you haven't thought about it much before, or you haven't you're not like a military history enthusiast, you might not realize that, oh yeah, mud. Mud is the sort of thing that you could write an entire book about just from the perspective of war and military operations. But that's what this book is.

When I think of mud and armed conflict. Obviously, you know, terrain and especially mud have played a big role in worse throughout history, but I think especially of Eastern Europe for some reason.

Yeah, big big war machines, big tanks stuck in the mud, or as as Wood mentions a time or two, the idea of one of these colossal tanks just going down a muddy hill, as if it were like a sled on a snowfield or something, you know, just out of control. Things like that. Occurring mud changes what you can and can't do in many instances with any with things ranging from infantry to horses to modern industrial war machines. But like I said, we'll get back to that more in the future. But I thought it was interesting that Wood opens just dealing with his basic ambiguity concerning mud and writes that, Okay, if we're going to be just very broad about it, it comes down to soil consisting of mineral and organic matter combined with moisture at such a level relative to the exact compositions of the soil to make it unstable and likely to move and flow underfoot or underhoof or under wheeler track, etc. Wood points out that while many military minds have considered mud and other soil issues beneath their strategic consideration, but they have always done so at their peril, because mud, as we'll get into later, does make a difference in war has come to very famously define certain war zones. He points out that not everyone has certainly ignored this fact, and in nineteen forty four, the US Army conducted a series of tests regarding mud. They're like, all right, let's get down to it. Let's classify some mud. Because we have only so many resources for our rubber tires, so we needed to decide where we need to send them, where we need to prioritize our best tires. And so this is a situation where we're dealing with sort of a narrowed perspective concerning mud. This is just mud concerning like, let me roll some vehicles across it. But they classified mud into two types and two subtypes. Okay, Type one bottomless mud. Now, this just means that the MUD's consistency cannot support a vehicle with tires that have twenty pounds of pressure, or that the underlying hard layer of earth beneath the mud beneath the layer of mud is too far beneath the vehicle's ground clearance.

Okay, so this sounds like dangerous mud.

Yeah, this is the mud that your vehicle is going to get stuck in and or sink into. And then type two is just all other types of mud. But this does feature two subtypes, Type A and type B. Type A has a quote unquote cleaning quality, meaning that it contains enough moisture to work as a liquid. So like this, like type A mud gets on your vehicle and you know, it kind of flows off. I mean it's I don't think cleaning quality means that your tank or your truck is going to be clean after the mud has a rent stock a little bit. Yeah, it flows away, but it's it's this a cleaning quality. Type B is adhesive or sticky. So this is the the mudd in type of mud. This is the type of mud that the the big pickup pickup truck driver seeks out when they go out into the wilderness to make sure that they return to city life with a vehicle completely encased in mud. Okay, So more on the military angle later on. So this is not necessarily a helpful way to understand mud as a whole, but rather to a way to underline that the meaning of mud kind of depends on what you're trying to do in it or through it, and mud therefore could be your threat or your treasure, depending on what you're looking to get out of the situation.

Very true. Now, I found an article that I thought was helpful. It was from two thousand and three in the Washington Post, and being in the Washington Post, I would say a little overly concerned with these specific types of mud found around the Washington d C. Metro area. But I'm mostly ignoring those parts because it does helpfully consult a bunch of soil scientists on the definitions and categories of mud. So it was called a World Gone Mud by Joel Aikenbach from June fifteenth, two thousand and three. First of all, it consults a researcher named Trish Steinhilbert from the University of Maryland Agricultural Nutrient Management Program, who says, you know, we would just call it wet soil. So that's one perspective. It's just wet soil, But then the article cites another soil physicist, or sorry, another soil researcher, this time a soil physicist also from the University of Maryland named Robert Hill, who says mud should be differentiated from merely wet soil because it has different physical properties. As commonly understood, like we've been saying, mud is sticky in a way that not all wet soils are, and this stickiness is due to the presence of a higher proportion of smaller particles, especially clay particles. So, as you probably know, soil is made from a mixture of different materials. Some of those materials are organic, so they can be you know, decaying organic matter or decaying bits of plants and animals and all that, but also inorganic matter, and we're going to focus on the inorganic matter for the moment. The inorganic solid particles that make up soil are generally produced by the erosion and breakdown of larger rocks over time, which can happen due to physical forces like wind, rain, and ice, or it can be due to break down by organisms like fungi and bacteria. And we all know soil can have different consistencies you stick your hands into the soil in one place, it just feels different than the soil in another place. One of the major factors that you can use to sort soil into different categories is the average particle size in the soil. So if particles are bigger than two millimeters, that's gravel. You know that's going to pop under your car tire. Particles of less than two millimeters in diameter but more than zero point zero five millimeters are sand. Then smaller than sand, you've got silt, which is made of particles less than zero point zero five million meters in diameter. And then at the very bottom, the finest grain soil is clay, which means particles smaller than zero point zero zero two millimeters in diameter. Now, apart from particle size, there are also some at least common chemical properties you'll find at these different areas, like they tend to derive from different types of minerals, like clay typically features a standard mineral constituent, which is hydrous aluminum philosilicates. But for the moment, we can just think about these as particles of different sizes. So by one definition, any sufficiently wet soil made of any mixture of these particles could be mud. But if you're going with the definition of mud as sticky slop that kind of sucks to the bottom of your shoes and you might get stuck in it usually means it's made up of mostly silt and clay sized particles. Silt sized and clay sized particles, and things get especially sticky if it has a lot of clay.

And again there's this fine line, Like I know, I instantly think back to some cave environments that I've been in, and mud at just the right consistency, it's like it's sticky, but you're not slipping in it. It's almost something you want to walk on. But that line is very thin between between that and like the treacherous mud that you will slip in. So it's fascinating when you start getting into the way this breaks down.

Yeah, is the mud grippy like maybe rubber? Or will it fly out from under you like a banana peel? And that does, I think come down to something having to do with the water content as well as the particle size. So if mud is wet soil or sticky wet soil, we've explained the soil part. It tends to be the smaller particle sizes clay sized and silt sized particles that make mud. But there's also the wetness angle. How wet does soil have to be for it to be mud. Here we get to the concept of cohesive soil and what are called Aderberg limits. So cohesive soils are soils that tend to stick or clump together as opposed to crumbling. Cohesive soils tend to have again more clay sized particles. Smaller particles stick together better, and cohesive soils can be in three states, depending on how wet they are. These states are non plastic, plastic, and viscous. Non Plastic means hard, you know, difficult to mold or deform. This is usually when they're dry. Cohesive soils dry up kind of hard like bricks, and they form tough earth, so you can think about like hard clay ground, you know what that's like. When cohesive soils get wet, though, they can cross one of these Aderberg limits, that the plastic limit and become plastic, so this means they become soft or moldable, think about wet clay, and then beyond that limit there's another limit, another limit which is the liquid limit, and this is the viscous stage where there's sort of like a liquid goop. So you can add water to non plastic soil until it crosses the plastic limit, becomes soft and mouldable, you can add more water until it crosses the liquid limit. Where the liquid limit is explained in this Washington Post article as if you cut a groove in the mud, the mud will flow back in to fill it. That's the liquid limit, which actually has some analogies in the culinary world, like if you ever did the back of the spoon test for the thickness of a sauce in the kitchen. The French term for that is nape, where if you like wipe your the tip of your finger along the back of a spoon coated in the sauce, it should leave a trail rather than having the sauce flow back in to fill the gap. That's nape.

One of the many culinary techniques in you just like jab your finger into things like.

Yeah, stick, yeah, stick your finger in the food.

Yeah, let the meat touch your face, and that will determine if it is the right temperature.

But so the definition of the liquid limit is that it does not pass the back of the spoon test if you cut a groove in it, it will flow back in to fill the gap. So it sounds to me like the definitional sweet spot for mud is a wet cohesive soil. It's made primarily of silt or clay sized particles, especially if there's a lot of clay sized particles that is above the plastic limit and below the liquid limit. Somewhere in there, though, I was thinking that even sort of fully liquid glop we do sometimes call mud, don't we, But that's not usually the first kind of substance I think of.

Right, right, Like, I come back to the example of mud pies. You know, I think a lot of us did this as a kid. If you're allowed to play in the mud, do you get some little like pie crust or little whatever, you know, cups and pans pour the mud up, slap the mud together, and then you set it in the sun too dry into mud cakes. But yeah, it's like if you're pouring it, if you're just complete all you know it is completely pouring it into the pan, that doesn't really feel like mud. That's just like mud water or something that's like on the way to mud. But not mud quite yet. The moisture still level is too high. And I guess in baking you have variations of that as well. Right like you said, the sauce is too runny, the batter is too runny, et cetera.

Oh, I think the mudpie test is a good one. And you know what, that actually brings me to the next thing I want to talk about, which is this might be something you've never considered before. Was there a time on Earth when it would have been really difficult to make a mud pie? I would argue, based on some research I've been reading about that, Yes, if you go back before five hundred million years ago, go to the pre Cambrian period, and you walk around on Earth's continents trying to find a place to make a mud pie, you're gonna probably strike out. You're gonna be out of luck, because there was a time basically before there was mud on land on Earth, or before there was very much mud to be found on land. So here I want to go to an article I was reading in the journal Science in the year twenty eighteen by Woodward Fisher, who is a Caltech geobiologist. The article is called Early Plants and the Rise of mud, and this article is primarily summarizing and contextualizing a study that was published by a couple of different authors in the same issue of the journal Science in twenty eighteen. This article is very good in putting these findings in context. So Fisher mentions that you know, life on Earth has several times that we know about reshaped fundamental geophysical features and processes at the Earth's surface. There are ways in which you could say that life has fundamentally changed the planet itself, at least what's happening on the surface and in the atmosphere. So perhaps the first example that will likely come to your mind is the oxygenation of the oceans in the atmosphere. It was the evolution of photosynthesis in cyanobacteria and other life forms that triggered this shift. You know, we didn't always have an oxygen atmosphere. Another major geophysical change triggered by life that Fisher mentions is the evolution of mineral skeletons by life forms, again, particularly algae, and the presence of those skeletons change the way that ocean floors are formed, and then subsequently the kinds of rock lay that would form when they solidified. Over the eons. But this article is focused on another discovery of this sort, how the evolution of land based plants changed the Earth by affecting mud. So the citation for the study here is William J. McMahon and Neil S. Davies. The article is called evolution of alluvial mud rock forced by early land plants again Journal Science, twenty eighteen. So when soil made mostly out of clay or silt sized particles gets compacted in the ground and lithifies into rock, the resulting rock layer is called mud rock, and there are many kinds of mud rock. When geologists look for layers of mud rock from the past, they notice something interesting. There is extremely little mud rock from river bottoms and floodplains before a geologic period in the history of the Earth. So if you look in the pre Cambrian era or the early Paleozoic era, there's very little mud rock on the continents. And I'll do a little refresher on the basic geologic timeline of the early to mid Palaeozoic, So you've got the Cambrian period. This is roughly five hundred million years ago. Before the Cambrian period, most life on Earth is small soft and unicellular, and then the Cambrian period represents a sort of explosion of life, a massive proliferation in the diversity of life forms. Life Forms get bigger, more complex, with hard body parts that get fossilized. So think of the age of trilobytes and anomalicaras. That's a period of like forty or fifty million years, roughly five hundred million years ago. And then you've got after that the Ordovician period, which is about four hundred and eighty five to four hundred and forty four million years ago, more diversification of life forms, primarily in the ocean, arthropods, molluscs, so forth, and the appearance of the very first primitive land plants. Then you've got the Silurian period, which is like four forty four to four nineteen million years ago. Note that this is separated from the previous era by the Ordovisian Silurian extinction event. There's often an extinction event separating these periods. This period shows diversification in fish and other marine fauna, but it's also important because of sort of a terrestrial revolution, the terrestrialization of many branches of life. Suddenly a lot more is happening on land instead of just in the ocean. So you have the evolution of vascular plants and terrestrial fungi, and these lead to changes in land ecosystems, including the ones we're talking about now. Also, land based arthropods diversify, so you get the ancestors of animals like spiders and insects and so forth. After that, from like four nineteen to three hundred and fifty nine million years ago, you've got the Devonian Period, sometimes called the Age of Fishes. Obviously there's a lot of fish diversification here, the terrestrial revolution continues, and then later in the Devonian period, this is the first time that you have the continents covered in forests of plants of the kind of things we would recognize as trees. But coming back to how this geologic timeline relates to mud, So in the Precambrian in continuing into the early Paleozoic, there is very little river mud rock showing up in the geologic strata. Instead, lithified river beds seem to contain sand and gravel, and as the Paleozoic era progresses, there is a rise in the formation of mud rocks in river deposits, which seems to indicate a global change in how sediment gets pushed and pulled around by rivers, and this change is associated with the colonization of the continents by plant life. There's an interesting analogy which is Mars. Mars we believe once had flowing rivers, but presumably did not have plants. And it also appears that Mars has very little mud rock in its river deposits.

Though we will come back to the topic of mud on Mars. Is there mud on Mars? You might ask, how we'll tune in to a future episode.

Mars needs goloshes. Yeah. So the authors of this twenty eighteen paper, McMahon and Davies, they wanted to zero in on this change in mud rock deposition in Earth's history and understand it better. So they were looking at samples of rock strata from ancient river beds before and after the land plant revolution all throughout this time period to measure the relative amount of mud rock corresponding to the different eras, and after crunching the numbers, they concluded that the fractional portion of mud rock the geologic strata rose by more than an order of magnitude an order of magnitude is ten times, so more than ten times increase in the proportion of mud rock I think in their abstract they actually say it was one point four orders of magnitude. This is after land plants evolved, so when plants colonized land, it made a huge profound change in what was happening with sediment, meaning mud, primarily in river bottoms and floodplains. The increase in these rocks made out of mud began in the late Ordovisian and continuing to the beginning of the Silurian, and this does implicate early land plants, but it's also interestingly it's earlier than the researchers expected to find it, perhaps in part because or perhaps their expectations for finding increases in mud rock in this period were low, because the earliest land plants here were they're really, I think mostly like bryophytes. They're these kind of little patchy green things that would resemble mosses or liver warts, so you know, we're not talking about jungles yet. Vascular plants meaning plants that have tissues that allow them to grow tall because they can conduct water and mineral nutrients up their stems. They start to appear in the late Silurian and early Devonian, but the earliest of these plants would only be a few centimeters off the ground and could only survive in wet environments. It isn't until again the Late Devonian, maybe like three hundred and seventy million years ago or so, that you first get what we would think of as forests, landscapes thick with relatively tall, vascular plants. But according to this research, even these earlier phases of puny, little baby plants, little mossy, liver warty type things, made a pretty big difference in how mud was distributed on the earth. But when you get to the later div and then into the Carboniferous period, there is an even bigger shift. This is the phase where there would again be forests of like impressive woody trees with deep root structures, like the things we think of as forests today. Rob I'm including an illustrated graph with a timeline from this article for you to look at. You can see that the amount of mud rock starts to go up during the period of like the bryophytes, these little primitive land plants, and then it really reaches its peak in the era of vascular plants, and especially like woody trees and later vascular plants, it seems like those deep root systems played a big role in that later period. However, I think, to come back on this, it's really worth noting that the Earth was not without mud as a planet before the proliferation of land plants. It looks like land plants played a huge role in forming these continental mud rock But there was mud before the plants. A sediment of clay and silt sized particles has been produced by erosion of surface rocks for billions of years. So what appears to have changed with the evolution of land plants is that mud started to stay on land, to stay on the continents, as opposed to just being blown or washed out to sea and settling on the seafloor. So the question is why did the evolution of plants lead to the retention of mud on land? And the article mentions a few ideas. One thing, first of all is that the authors say that the presence of land plants may actually have helped produce more mud particles to begin with, lead to erosion processes that would produce more mud. Now, how would plants help produce more mud well. For one thing, I was reading this in another article that plants with strong root structures actually break and crumble large pieces of rock. Those roots can break up the rocks physically, crack and break them, but can also lead to changes in the chemical composition of soil that break down rocks even further into smaller pieces. But again, we don't need plants for mud to exist. There's always been these mud sized the soil particles. So what other changes did plants introduce? Fissure rites quote. It is therefore likely that early plants affected the mechanics of flood plain construction. For example, the presence of plants on the landscape decreases erosion rates, and thus it was long hypothesized that erosion, in particular by wind, removed sediment from pre vegetated landscapes. Even if mud was deposited on pre vegetated floodplains, its removal by erosion might have been efficient. So before there were plants on land, it was just too easy for small particles of soil to get washed out to the sea one way or another. They could get by wind, they could get carried along by the flow of water after storms and rain, and they would all just end up on the floor of the ocean. So it seems like plants and their root structures helped prevent small soil particles that form mud from escaping into the sea. But it doesn't stop there. Plants and the mud that the plants retained changed how rivers form, Fisher writes quote. In addition to an inhibiting erosion, plants also interact with river flows and promote the deposition of fine grained sediment. This can help armor river banks and slow their lateral migration. Such process might also aid in preserving muddy floodplain deposits, so plants might sort of help stabilize the structure of rivers and keep the banks from drifting all over the place and changing too rapidly, especially during floods, which helps protect the mud that gathers in floodplains and keeps it there.

Fascinating. Fascinating that the plant's kind of corralling the mud in many cases. And I think if you've ever been in a like especially I'm thinking of like estuary type environments that I've visited, Like you see these elaborate root systems, You see the mud and the sediment. So that's what I'm picturing during all of this.

Oh yeah, yeah, yeah. And so actually, to help us better picture it, I found another great article that's on the same subject, that's on this type of research, but it includes a lot more context and imagery to help us understand it. So this other article was called the Origin of Mud from a magazine called Knowable, written by a writer named Laura Poppic, published in August twenty twenty, and I thought this was interesting. This article starts with this anecdote about one of the two authors of that twenty eighteen study, the geologist Neil Davies. It starts with this anecdote about him picking through a large fossil formation from about four hundred and sixty million years ago in Bolivia containing just tons of smothered fish fish that all seemed to die at the same time. And apparently this is not uncommon for marine fossil formations from this period. You'd have large numbers of fossil fish living near an ancient shoreline that appear to have all died around the same time by being choked by mud. So the explanation for this is probably that there's all this muddy sediment that is suddenly washed into the water into the ocean along the shore, possibly by a storm, and then the fish underwent death by mud. So this was four hundred and sixty million years ago before the proliferation of land plants Poppic writes quote magnified this effect globally, and the impacts would have been substantial, not just on coastal life, but on the landscape of the entire planet. Before plants, rivers would have stripped continents of silt and clay key constituents of mud, and sent these sediments to the seafloor. This would have left continents full of barren rock and seas with smothered fish.

So primordial muddy oceans.

Yes, especially at least around like where the rivers would drain into them, and landscapes with very little mud at all, you know, I mean, you can just let your dog run all over it and then come inside the house. There's no problem.

Yeah. I keep wondering if a wellsy and time traveler would have to bring his Victorian galoshes in visiting this time period.

But of course plants change all of this. Vegetation, especially along river banks, gave mud sized particles something to cling to, and so the mud stayed on land rather than getting washed or blown out to sea. And in the words of Neil Davies, this retention of mud on land quote fundamentally changed the way the world operates.

Wow.

And so there are some examples of how this mud revolution changed the continents, changed the world. Essentially, one thing is that the geological record reveals that before the evolution of plants, earth rivers probably would have looked more like the comparison that Poppuic uses is the rivers found around the Gravelly Coast of Alaska today, And she describes these I'm trying to say, so like, imagine if you've ever seen the kinds of branching, braided channels you see as a stream flows into the ocean across a sandy beach. So not mud, but you've seen like a stream flowing over a sandy beach.

Yeah.

Yeah. What you'll usually notice is there is not a very strong, unified channel. Instead, there's just lots of little threads of channels crisscrossing and always changing. This is referred to in several sos as I looked at as a braided structure of alluvial flow. The introduction of plants seems to have changed this by holding mud in place, and the mud being sticky would solidify the form of river banks, and this led to stable single channel rivers with fixed banks and boundaries, rather than these little shrubs of different rivulets changing all the time, so you end up with the curving, defined s shaped rivers that we see today. These rivers are made possible by the presence of mud, which is held on land by plants. Now, these changes in rivers had all kinds of interesting biological consequences. For example, the bins in a river can alter things like the temperature and chemistry and the water compared to a straight flowing river, which can create different micro environments along the river's length, so that gives all kinds of different little tiny eco systems and habitats that organisms would have to adapt to. But the presence of mud itself is also biologically relevant because mud is a habitat, so it takes special skills and evolutionary adaptations to live in mud and move around and navigate your way through it. For example, it takes different types of adaptations for movement for a small animal to get through mud than it does to get through sand or some other type of surface. And Poppy's article consults a geologist at the University of Oxford named Anthony Shalito on this subject. I thought this was so interesting, so Shaldo says, here, I'm quoting from popic quote. To get through mud, and animals such as a worm, creates cracks to shuffle through by contracting its body, extending it, squeezing water out of the way, and moving forward. This is mechanically different from traveling through sand, which requires an animal to excavate material out of the way. Chiledo says, so early land worms and insects would have had to evolve body parts equipped to deal with muckier movements, but then in turn the animals that adapt to those muddy environments change them because Poppic then sites a paleobiologist from Yale named Lydia Tehran who says that you know, like these animals living in the muddy soil around river banks, they dig in the mud, they excavate the mud, and this for one thing, it affects the chemistry of the mud, but it also sort of like breaks and loosens it up, which allows the mud to further disperse throughout the rivers and then also across flood plains, so you know, the valleys where rivers form between the higher areas of the land. So because you get these single channel s shaped rivers with more defined banks, you get these downstream processes that lead to the build up of muddy flood plains around them, which don't form as easy along the kind of rivers you see forming in sand or gravel.

This is fascinating. I'm looking forward to getting back to some of this in our episode that's going to deal more with the specifics of some of the animals in the world today that make their home on the mud.

Oh yeah, absolutely. But I love this story because it's just one of these amazing examples of how much, you know, sometimes we don't stop to appreciate the inner play between like earth and water and life, and the way that they all are constantly changing each other. That there's this like massive, you know, process like the mud revolution caused by the evolution of plants on land further gives rise to all of these these changes in land based life, which helps give give rise to more changes in like how mud accumulates and how sediment is distributed in floodplains and so forth. So I guess by way of research, we have once again and arrived at cliche. But sometimes that's how it is. I mean, it's the life and the inorganic systems that support life, the surface of the earth. It's a web of interactions.

Yeah, And I think it is easy to sort of fall back on just sort of the school textbook mental image of fish flops onto a beach, fish flops onto some rocks, and now life on earth has begun, you know, like sort of not considering mud is this vital realm of evolution and transference.

And human culture and technology, Because this is another thing that Poppic gets into in her article, like she quotes Woodward Fisher talking about how there are still things that we don't fully understand about mud and the way that riverbanks work and stuff, and this research could help contribute to that, for example, by giving us better ideas of how to do river engineering projects like dam construction. You know, if you have a better idea of the way that vegetation controls the flow of rivers and how the banks of the rivers change and respond to flood conditions, you could better anticipate and prevent, for example, river engineering failures. The example given in the article here is like flooding along the Mississippi River. But you know, this is of concern to societies all around the world.

All of this reminds me of that great quote from T. S. Eliot from four Quartets quote. I do not know much about gods, but I think that the river is a strong brown god, sullen, untamed and intractable.

Well, that's beautiful. And to know that that god may have been formed out of many other lesser gods over time by the accumulation of mud by plants. Oh, this is just a random thing I remembered, but I wanted to throw it in quickly. Another interesting thing mentioned in that popic article is the idea that once forests are formed on land, they can also help contribute to the accumulation of mud on the continents because they act as a sort of filter for dust and sediment that is blown by the wind. So the wind, you know, you can imagine it picking up fine grain particles of soil, clay, and silt, blowing them around when they're dry, and normally they just get blown out to sea. But if there are forests, they get stopped by the forests, they get stuck in the sort of the sieve of the trees they fall to the earth, and then they can accumulate and become mud on the forest floor, flow down into a river over time with the wash of the rains and so forth, and then become new muddy banks.

It's amazing. Yeah, it's so easy to take mud for granted, because, like I say, if you're just coming at it from the perspective of someone who wants to go on a walk in the woods, and then mud is what happens when when something has failed or or conditions are not optimal. But this, this look at the MUD's roll in the emergence of life and the sort of the construction of the world as we know it, Yeah, really really casts it in.

A different But we're by no means done with this topic. I think we should wrap it up for today. But when we come back, we will be talking about mud and warfare, Mud in human civilization, Mud on Mars, mud and animal behavior and more mud, monsters. There's all kinds of stuff. Yeah.

Yeah, So this is one of those where we definitely don't know how many episodes it'll be, so we can't give you a heads up that this is going to be two episodes, three episodes, We're just going to have to listen to the mud and follow the mud and let it take us. Like someone's stepping in it on a muddy path. We just got to let it see where we go, how far we're going to slide into mud? All right, Well, on that note, we're going to go ahead and close it out, but we'll be back next time with more mud. So just remember that. Our core episodes of Stuff to Blow Your Mind publishing the Stuff to Blow Your Mind podcast feed on Tuesdays and Thursdays. Mondays we do listener mail, Wednesdays we do a short form artifact or monster Effect, and on Fridays we do Weird House Cinema. That's our time to set aside most serious concerns and just talk about a weird film.

Huge thanks to our excellent audio producer JJ Posway. If you would like to get in touch with us with feedback on this episode or any other, to suggest a topic for the future, or just to say hello, you can email us at contact at stuff to Blow your Mind dot com.

Stuff to Blow Your Mind is production of iHeartRadio. For more podcasts from iHeartRadio, visit the iHeartRadio app Apple Podcasts or Wherever you're listening to your favorite shows,

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