July 6, 2023 • 46 mins
What exactly is mud? Where does it occur and how does it factor into animal behaviors and human activities? In this multi-episode Stuff to Blow Your Mind exploration, Rob and Joe immerse themselves in the mysteries of mud.
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Speaker 1 (00:03):
Welcome to Stuff to Blow Your Mind, a production of iHeartRadio.
Speaker 2 (00:12):
Hey, welcome to Stuff to Blow your Mind. My name
is Robert.
Speaker 3 (00:15):
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
(00:37):
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
(00:58):
much your classic poem with you know, 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
(01:19):
the mud of the Nile River, spawns monsters, and Spencer
writes quote as when old Father Nihilis 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
(01:40):
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.
(02:01):
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
Nihilus inundation, infinite shapes of creatures men do find informed
in the mud on which the sun hath shined. So
(02:24):
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,
(02:46):
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 flour or something. But I also like it
because it imagines the mud in the floodplain of a
(03:10):
great river like the Nile as a 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
(03:31):
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,
(03:53):
and you don't know what you might find.
Speaker 2 (03:55):
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
(04:17):
role in especially an ancient Egyptian belief and mythology. But yeah, this,
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
(04:37):
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. Yeah, it
(05:00):
does seem to have this dual nature, at least from
the human vantage point.
Speaker 3 (05:04):
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.
Speaker 2 (05:20):
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 mmama mud, Right, I guess that's the
(05:40):
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.
Speaker 3 (05:48):
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,
(06:08):
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
(06:32):
might be in the eye of the beholder of the
beat or of the bee treader.
Speaker 2 (06:36):
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
(06:56):
where you're coming from, you know, like if you were
a domestic 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
(07:18):
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
(07:40):
and military operations. But that's what this book is.
Speaker 3 (07:43):
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.
Speaker 2 (07:54):
Yeah, big big war machines, big tanks stuck in the mud,
or has a 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
(08:17):
can't do in many instances 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 this basic ambiguity concerning mud and writes that, Okay,
(08:37):
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
(09:02):
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
(09:22):
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
(09:45):
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
(10:06):
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.
Speaker 3 (10:17):
Okay, so this sounds like dangerous mud.
Speaker 2 (10:20):
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
(10:42):
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 sofa 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 mud
(11:04):
in type of mud. This is the type of mud
that 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
(11:25):
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.
Speaker 3 (11:38):
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
(12:03):
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 Steinhilber
from the University of Maryland Agricultural Nutrient Management Program, who says,
you know, we would just call it wet soil, So
(12:23):
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
(12:47):
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
(13:09):
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,
(13:32):
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
(13:56):
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
(14:19):
zero point zero five millimeters 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
(14:40):
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
(15:03):
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.
Speaker 2 (15:23):
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
(15:46):
will slip in. So it's fascinating when you start getting
into the way this breaks down.
Speaker 3 (15:52):
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
(16:12):
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 adderberg limits. So Cohesive soils
are soils that tend to stick or clump together as
(16:34):
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 difficult to mold or deform. This
(16:58):
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 Adderberg limits, that the plastic limit,
and become plastic. So this means they become soft or moldable,
(17:20):
So 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
(17:40):
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 back of the spoon test for the thickness of
(18:02):
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 that's nape.
Speaker 2 (18:17):
One of the many culinary techniques in Abo. You just
like jab your fingers into things like.
Speaker 3 (18:21):
Yeah, stick, yeah, stick your finger in the food.
Speaker 2 (18:24):
Yeah, let the meat touch your face, and that will
determine if it is the right temperature.
Speaker 3 (18:29):
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
(18:49):
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.
Speaker 2 (19:07):
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, you get some little like pie
crusts or just 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.
(19:30):
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 levels 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,
(19:51):
et cetera.
Speaker 3 (20:01):
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'd never considered before. Was there a time
on Earth when it would have been really difficult to
make a mudpie? I would argue, based on some research
I've been reading about that, Yes, if you go back
(20:23):
before or 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 mudpie, You're
gonna probably strike out. You're going to be out of luck,
because there was a time basically before there was mud
on land on Earth, or before there was very much
(20:46):
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
(21:10):
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
(21:33):
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
(21:56):
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
(22:18):
formed and then subsequently the kinds of rock layers 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
(22:40):
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 the resulting rock layer
(23:02):
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
certain geologic period in the history of the Earth. So
(23:23):
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,
(23:47):
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 trilobites and anomalo icaris. That's a period of
(24:07):
like forty or fifty million years, roughly five hundred million
years ago. And then you've got after that the Ortavician 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.
(24:29):
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 Ordovician
Silurian extinction event. There's often an extinction event separating these periods.
This period shows diversification in fish and other marine fauna.
(24:50):
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
(25:11):
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. And then 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
(25:32):
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 Palaeozoic, there is very little river
(25:55):
mud rock showing up in the geologic strata. Instead, lithified
riverbeds see 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
(26:17):
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.
Speaker 2 (26:38):
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.
Speaker 3 (26:48):
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
(27:09):
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 in 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
(27:32):
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
(27:54):
out of mud began in the late Ordovician 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
(28:15):
in this period were low because the earliest land plants
here they're really puny, 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
(28:38):
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
(28:59):
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 wardy type things, made a pretty big difference in
how mud was distributed on the earth. But when you
(29:19):
get to the later Devonian, 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
(29:43):
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 the those deep root systems played a big
role in that later period. However, I think to come
(30:06):
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 rocks, but there
was mud before the plants. A sediment of clay and
silt sized particles has been produced by erosion of surface
(30:29):
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
(30:52):
of mud on land? And the article mentions a few ideas.
One thing, first of all, is that the authors say
the presents 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
(31:14):
this in another article that plants with strong root structures
actually break and crumble larger 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.
(31:37):
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, remove sediment from
(32:01):
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 blown by wind, they could get carried along by
(32:23):
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
(32:47):
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
(33:08):
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.
Speaker 2 (33:21):
Fascinating, fascinating that the plants 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.
Speaker 3 (33:42):
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 like 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,
(34:05):
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
(34:27):
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
(34:50):
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,
(35:12):
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.
Speaker 2 (35:30):
So primordial muddy oceans.
Speaker 3 (35:32):
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.
Speaker 2 (35:43):
Yeah. I keep wondering if a wellsy and time traveler
would have to bring his Victorian galoshes in visiting this
time period.
Speaker 3 (35:52):
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.
Speaker 2 (36:14):
Wow.
Speaker 3 (36:24):
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's rivers probably would have looked more like
the comparison that poppyic uses is the rivers found around
the Gravelly Coast of Alaska today, and she describes these
(36:49):
I'm trying to think 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.
Speaker 2 (37:05):
Yeah, yeah.
Speaker 3 (37:06):
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 sources. I looked at as a braided structure of
alluvial flow. The introduction of plants seems to have changed
(37:28):
this by holding mud in place, and the mud being
sticky would solidify the form of riverbanks, 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
(37:49):
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
(38:09):
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 ecosystems
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
(38:33):
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 Poppix article consults
a geologist at the University of Oxford named Anthony Shalito
(38:56):
on this subject. I thought this was so interesting, so
Shlido 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
(39:18):
to excavate material out of the way. Chiliedo 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 cites a palaeobiologist from Yale
(39:38):
named Lydia Taran who says that you know, like these
animals living in the in the muddy soil around riverbanks,
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
(39:59):
and also across floodplains. 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 easily along the kind of rivers
(40:22):
you see forming in sand or gravel.
Speaker 2 (40:25):
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.
Speaker 3 (40:38):
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 us like the mud revolution
(41:01):
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 arrived at cliche. But sometimes that's
(41:23):
how it is. I mean, it's the life and the
inorganic systems that support life, the surface of the earth.
It's a it's a web of interactions.
Speaker 2 (41:31):
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
onto some rocks, and now life on earth has begun,
you know, like sort of not not considering mud. Is
this vital realm of evolution and transference.
Speaker 3 (41:52):
And human culture and technology, because this is another thing
that Poppic gets into in her article, like she quotes
would 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
(42:13):
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.
(42:33):
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.
Speaker 2 (42:42):
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.
Speaker 3 (42:56):
Well, that's beautiful. And to know that that god may
have been formed 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
(43:20):
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 salt, 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
(43:40):
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.
Speaker 2 (43:55):
It's amazing. Yeah, it's so easy to take mud for granted, because,
like as 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 our conditions are not optimal.
But but this this this look at the MUD's role
in the emergence of life and sort of the construction
(44:17):
of the world as we know it. Yeah, it really
really casts it in a different light.
Speaker 3 (44:21):
But we are 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 and human civilization, Mud on Mars, Mud
and animal behavior and more mud, monsters. There's all kinds
of stuff. Yeah.
Speaker 2 (44:37):
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 stepping in it on
a on a on a muddy path. We's got to
let it see where we go, how far we're going
(44:57):
to slide in the 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
(45:19):
a weird film.
Speaker 3 (45:21):
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 Stuff to Blow Your Mind
dot com.
Speaker 1 (45:42):
Stuff to Blow Your Mind is production of iHeartRadio. For
more podcasts from my Heart Radio, visit the iHeartRadio app,
Apple Podcasts, or wherever you listening to your favorite shows.
Speaker 2 (46:00):
Fred is Fras with Ratatatata
Welcome to Stuff to Blow Your Mind, a production of iHeartRadio.
Speaker 2 (00:12):
Hey, welcome to Stuff to Blow your Mind. My name
is Robert.
Speaker 3 (00:15):
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
(00:37):
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
(00:58):
much your classic poem with you know, 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
(01:19):
the mud of the Nile River, spawns monsters, and Spencer
writes quote as when old Father Nihilis 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
(01:40):
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.
(02:01):
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
Nihilus inundation, infinite shapes of creatures men do find informed
in the mud on which the sun hath shined. So
(02:24):
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,
(02:46):
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 flour or something. But I also like it
because it imagines the mud in the floodplain of a
(03:10):
great river like the Nile as a 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
(03:31):
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,
(03:53):
and you don't know what you might find.
Speaker 2 (03:55):
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
(04:17):
role in especially an ancient Egyptian belief and mythology. But yeah, this,
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
(04:37):
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. Yeah, it
(05:00):
does seem to have this dual nature, at least from
the human vantage point.
Speaker 3 (05:04):
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.
Speaker 2 (05:20):
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 mmama mud, Right, I guess that's the
(05:40):
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.
Speaker 3 (05:48):
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,
(06:08):
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
(06:32):
might be in the eye of the beholder of the
beat or of the bee treader.
Speaker 2 (06:36):
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
(06:56):
where you're coming from, you know, like if you were
a domestic 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
(07:18):
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
(07:40):
and military operations. But that's what this book is.
Speaker 3 (07:43):
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.
Speaker 2 (07:54):
Yeah, big big war machines, big tanks stuck in the mud,
or has a 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
(08:17):
can't do in many instances 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 this basic ambiguity concerning mud and writes that, Okay,
(08:37):
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
(09:02):
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
(09:22):
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
(09:45):
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
(10:06):
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.
Speaker 3 (10:17):
Okay, so this sounds like dangerous mud.
Speaker 2 (10:20):
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
(10:42):
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 sofa 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 mud
(11:04):
in type of mud. This is the type of mud
that 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
(11:25):
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.
Speaker 3 (11:38):
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
(12:03):
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 Steinhilber
from the University of Maryland Agricultural Nutrient Management Program, who says,
you know, we would just call it wet soil, So
(12:23):
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
(12:47):
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
(13:09):
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,
(13:32):
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
(13:56):
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
(14:19):
zero point zero five millimeters 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
(14:40):
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
(15:03):
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.
Speaker 2 (15:23):
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
(15:46):
will slip in. So it's fascinating when you start getting
into the way this breaks down.
Speaker 3 (15:52):
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
(16:12):
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 adderberg limits. So Cohesive soils
are soils that tend to stick or clump together as
(16:34):
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 difficult to mold or deform. This
(16:58):
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 Adderberg limits, that the plastic limit,
and become plastic. So this means they become soft or moldable,
(17:20):
So 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
(17:40):
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 back of the spoon test for the thickness of
(18:02):
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 that's nape.
Speaker 2 (18:17):
One of the many culinary techniques in Abo. You just
like jab your fingers into things like.
Speaker 3 (18:21):
Yeah, stick, yeah, stick your finger in the food.
Speaker 2 (18:24):
Yeah, let the meat touch your face, and that will
determine if it is the right temperature.
Speaker 3 (18:29):
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
(18:49):
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.
Speaker 2 (19:07):
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, you get some little like pie
crusts or just 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.
(19:30):
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 levels 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,
(19:51):
et cetera.
Speaker 3 (20:01):
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'd never considered before. Was there a time
on Earth when it would have been really difficult to
make a mudpie? I would argue, based on some research
I've been reading about that, Yes, if you go back
(20:23):
before or 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 mudpie, You're
gonna probably strike out. You're going to be out of luck,
because there was a time basically before there was mud
on land on Earth, or before there was very much
(20:46):
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
(21:10):
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
(21:33):
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
(21:56):
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
(22:18):
formed and then subsequently the kinds of rock layers 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
(22:40):
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 the resulting rock layer
(23:02):
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
certain geologic period in the history of the Earth. So
(23:23):
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,
(23:47):
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 trilobites and anomalo icaris. That's a period of
(24:07):
like forty or fifty million years, roughly five hundred million
years ago. And then you've got after that the Ortavician 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.
(24:29):
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 Ordovician
Silurian extinction event. There's often an extinction event separating these periods.
This period shows diversification in fish and other marine fauna.
(24:50):
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
(25:11):
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. And then 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
(25:32):
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 Palaeozoic, there is very little river
(25:55):
mud rock showing up in the geologic strata. Instead, lithified
riverbeds see 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
(26:17):
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.
Speaker 2 (26:38):
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.
Speaker 3 (26:48):
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
(27:09):
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 in 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
(27:32):
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
(27:54):
out of mud began in the late Ordovician 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
(28:15):
in this period were low because the earliest land plants
here they're really puny, 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
(28:38):
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
(28:59):
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 wardy type things, made a pretty big difference in
how mud was distributed on the earth. But when you
(29:19):
get to the later Devonian, 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
(29:43):
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 the those deep root systems played a big
role in that later period. However, I think to come
(30:06):
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 rocks, but there
was mud before the plants. A sediment of clay and
silt sized particles has been produced by erosion of surface
(30:29):
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
(30:52):
of mud on land? And the article mentions a few ideas.
One thing, first of all, is that the authors say
the presents 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
(31:14):
this in another article that plants with strong root structures
actually break and crumble larger 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.
(31:37):
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, remove sediment from
(32:01):
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 blown by wind, they could get carried along by
(32:23):
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
(32:47):
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
(33:08):
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.
Speaker 2 (33:21):
Fascinating, fascinating that the plants 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.
Speaker 3 (33:42):
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 like 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,
(34:05):
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
(34:27):
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
(34:50):
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,
(35:12):
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.
Speaker 2 (35:30):
So primordial muddy oceans.
Speaker 3 (35:32):
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.
Speaker 2 (35:43):
Yeah. I keep wondering if a wellsy and time traveler
would have to bring his Victorian galoshes in visiting this
time period.
Speaker 3 (35:52):
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.
Speaker 2 (36:14):
Wow.
Speaker 3 (36:24):
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's rivers probably would have looked more like
the comparison that poppyic uses is the rivers found around
the Gravelly Coast of Alaska today, and she describes these
(36:49):
I'm trying to think 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.
Speaker 2 (37:05):
Yeah, yeah.
Speaker 3 (37:06):
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 sources. I looked at as a braided structure of
alluvial flow. The introduction of plants seems to have changed
(37:28):
this by holding mud in place, and the mud being
sticky would solidify the form of riverbanks, 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
(37:49):
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
(38:09):
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 ecosystems
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
(38:33):
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 Poppix article consults
a geologist at the University of Oxford named Anthony Shalito
(38:56):
on this subject. I thought this was so interesting, so
Shlido 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
(39:18):
to excavate material out of the way. Chiliedo 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 cites a palaeobiologist from Yale
(39:38):
named Lydia Taran who says that you know, like these
animals living in the in the muddy soil around riverbanks,
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
(39:59):
and also across floodplains. 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 easily along the kind of rivers
(40:22):
you see forming in sand or gravel.
Speaker 2 (40:25):
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.
Speaker 3 (40:38):
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 us like the mud revolution
(41:01):
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 arrived at cliche. But sometimes that's
(41:23):
how it is. I mean, it's the life and the
inorganic systems that support life, the surface of the earth.
It's a it's a web of interactions.
Speaker 2 (41:31):
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
onto some rocks, and now life on earth has begun,
you know, like sort of not not considering mud. Is
this vital realm of evolution and transference.
Speaker 3 (41:52):
And human culture and technology, because this is another thing
that Poppic gets into in her article, like she quotes
would 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
(42:13):
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.
(42:33):
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.
Speaker 2 (42:42):
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.
Speaker 3 (42:56):
Well, that's beautiful. And to know that that god may
have been formed 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
(43:20):
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 salt, 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
(43:40):
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.
Speaker 2 (43:55):
It's amazing. Yeah, it's so easy to take mud for granted, because,
like as 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 our conditions are not optimal.
But but this this this look at the MUD's role
in the emergence of life and sort of the construction
(44:17):
of the world as we know it. Yeah, it really
really casts it in a different light.
Speaker 3 (44:21):
But we are 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 and human civilization, Mud on Mars, Mud
and animal behavior and more mud, monsters. There's all kinds
of stuff. Yeah.
Speaker 2 (44:37):
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 stepping in it on
a on a on a muddy path. We's got to
let it see where we go, how far we're going
(44:57):
to slide in the 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
(45:19):
a weird film.
Speaker 3 (45:21):
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 Stuff to Blow Your Mind
dot com.
Speaker 1 (45:42):
Stuff to Blow Your Mind is production of iHeartRadio. For
more podcasts from my Heart Radio, visit the iHeartRadio app,
Apple Podcasts, or wherever you listening to your favorite shows.
Speaker 2 (46:00):
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