Episode 6 - What on Earth is geological time?! - Proterozoic & Paleozoic

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In this episode of What On Earth?!, we’re diving into geological time. This is Part 1.

Ever wondered how scientists make sense of 4.6 billion years of Earth history? How do you even begin to divide that into something understandable? And why do some chapters of Earth’s past end so dramatically?

We’re going all the way back to the Precambrian and the Paleozoic, a time when Earth was a very different place.

We start in the Precambrian, where life is tiny, the atmosphere is changing, and the planet is still forming into the layered, dynamic system we know today. Think rising oxygen, shifting supercontinents, and even moments where ice may have covered almost the entire globe.

Then we move into the Paleozoic, where life really starts to get interesting. Oceans fill with bizarre creatures, early fish begin to appear, and for the first time ever, life starts making the move onto land. Plants, insects, and eventually vertebrates begin exploring a completely new world.

Along the way, we touch on moving continents, changing climates, and the big events that shape life on Earth, including one of the most dramatic mass extinctions in our planet’s history.

If you like big stories, strange lifeforms, and understanding how our planet became what it is today, this episode is for you.

Transcript

SPEAKER_04 1:18

We know how to talk about how to guide you through the the basics, the the main events, or the ones I find interesting.

SPEAKER_05 1:45

So yes, this recording is very biased, just for your information at the start. I think we are first gonna explain a bit about the how time works in geology because there's there's many ways we talk about time and history that we first need to need to show. So you have time and time, just like we would explain time like this many years ago, that many years ago, and many of the like the whole earth history is divided in certain time frames or certain patterns or certain like pieces that are grouped by that are usually ending in some natural disaster or another big event on earth where it ends. And if we m talk about time in time, we call it early, middle, late of this period. If we talk about it in rocks, so you can see time in rocks as well, we call it lower, middle, upper. So the the terminology is a bit different between these two.

SPEAKER_04 2:42

Why why do we do that? Why do we say lower middle upper? Does it connect with the way uh like the rocks are found?

SPEAKER_05 2:49

Yeah, so the the general assumption is that you breathe time in rocks from low to high because sediment is put atop each other and every top layer of sediment is therefore newer than the bottom one, which is a very limited first view because obviously a lot of sediments have moved into mountains or uplifted or curled, some are even upside down, but that's the basic of how it's yeah, yeah, basic principle of how it's formed, and therefore how we call it, I would say. Um so this episode's gonna be a quick glance through plate tectonics, climate, and large changes in flora and fauna.

SPEAKER_04 3:29

Exciting, exciting, yes. So especially excited about natural disasters.

SPEAKER_05 3:35

There's there's very little about natural disasters, to be honest.

SPEAKER_04 3:38

No, like no dramatic events like you know, eating popcorns, like oh my god, what's gonna happen next?

SPEAKER_05 3:43

I mean there is, but those are the least interesting in my opinion. But I'm I'm glad you're excited at the beginning. Then there's one thing I'm also obligated to tell you about, which is the the golden pins. Geologists put in rocks to determine certain time jumps. So for example, the how do you say this? My English is getting worse by the day. If you go from one time period to another, there's m usually something distinct that you can see in many layers of rocks in many places on earth um that defines this change. Um but there's always one location or one outcrop of rocks or one thing where it is defined. It's like uh Oxford dictionary for rocks, yeah. Yeah, reference point. And they put actually put a golden pin in this rock, they hammer it in, it's a whole ceremony. Yeah, yeah, yeah.

SPEAKER_04 4:33

So you can like visit these sites and see this golden pin.

SPEAKER_05 4:36

Yeah, yeah. It's probably bronze though, or something lesser. Yeah, I don't think they put the gold there. But they call it the golden pin, and there are these sites where they define this boundaries. Um we also have to mention the assumption or the scientific evidence that the earth is 4.6 billion years old, and we count back to modern days.

SPEAKER_04 5:00

How do we know that? From where did we get the evidence that the age of the earth?

SPEAKER_05 5:05

Um, I think there are many ways to determine it. One of them by decay of certain elements, so radioactive decay. I don't think it's I mean, we're talking about billion years, it's not like on the year precise.

SPEAKER_02 5:20

Yeah.

SPEAKER_05 5:21

Because it's so long ago and we don't know much about this time. There's not much preserved as well. But yeah, I think it's mostly decay, right?

SPEAKER_04 5:26

Yeah, yeah, it's mostly, I think, zircons, or at least this is this is what I know it, that we know the age of the earth by dating zircons. I think this is really interesting science that uh we can take zircons are minerals, and then by measuring how much uranium to lead you have there, you can determine the age. Let's maybe talk about it later when we maybe will be talking about how all the methods we use for for dating. But yeah, it's it's a whole science with like within itself. So you see that it has you know, the listeners know that it's just not that simple because everything overlaps with each other, and you can be tikah who loves sediment, but in the same time you have to deal with zircons, which are something I really like because they are in magmatic and metamorphic rocks.

SPEAKER_05 6:16

Yeah, yeah, I think it's a very precise science. My interest lies more in the storytelling, so of course how and when and how precise it is. I believe it, it's cool, it's just not something my expertise has lies. So the way we talk about this billion years ago, million years ago, if you if you read in the articles, we say B A, so billion years ago, MA million years ago, and then you count back to now, so now it's like zero million years ago because we are in the present. Um, and we basically have four big divisions in we describe so it's the the ancient time, the precambrian, then we have the the or the protozoic, it depends on which order of magnitude you take. Then uh we have the Paleozoic, so it's old time, Mesozoic, middle time, Cenozoic, recent time, and recent is a very weird way of saying like 66 million years ago till now.

SPEAKER_04 7:17

I'm just gonna yesterday by by the Earth standard.

SPEAKER_05 7:21

Yeah, but if if you think about it, like 4.6 billion billion years ago, like let me emphasize the billion here.

SPEAKER_04 7:28

Yeah, 66 million years ago doesn't sound like not the same magnitude, but it's still a lot of time, you know. If you think that humans live, let's say, I don't know, up to a hundred something years ago, years, like that's it. And then like you have millions and billions. That's we are a speck in the universe of time.

SPEAKER_05 7:48

Yeah, yeah. But for this episode, we're gonna talk about the pre Cambrian or Proterozoic and then Paleozoic eras because it's just too much to cover the more recent stuff. Also, I think it's more fun to talk to someone else about these times, so we'll arrange that later. Um, so we're talking about the the time from 4.6 billion years ago to 541 million years ago first, which is called the Precambrian. And you immediately see that it's like four billion years we're talking about. It's a large chunk of time, and it's the oldest chunk of time because there was very little to measure, because either everything is gone or eroded away or gone by magma, or we just don't see it at the surface. So we don't know much about it. But there is there's little things we know. If we talk about the the first half of this chunk of time, so until 2.5 billion years ago, we talk about the Hadean and the Archean, and you hear by the name Hadean, Hades, hell, hell, yeah, hot was warm and very inhospitable on Earth at that time. The formation of the Earth, as you talked about a little bit in your formation of the solar system as well, it was all very hot, it was all very volatile because of all the impact craters as well. So there was it was very warm and the earth was still cooling down into its layers, um, which it was busy with for the first two and a half billion years of its existence. So it it differentiated based on density. So we've have create have the formation of layers with the crust, the mantle, and then the core. There are still a lot of impact creators. Uh impacts on, which is like in this book, they say the impact created the moon.

SPEAKER_04 9:33

Or started.

SPEAKER_05 9:34

I think it's debatable, right? There's a lot of theory about this.

SPEAKER_04 9:38

We will cover this more in the episode when I will be nerding out about my PhD. But uh generally the giant impact hypothesis, let's say, largely is accepted for the lack of having a better explanation, but they are alternative the theories. One of them would uh hypothesis, which I actually one of them I really it's very interesting. Uh let's say there's for sure something smashing into the earth.

SPEAKER_05 10:03

From my understanding, something smashed in the earth, some other parts segregated, form it formed the moon. Um, which has a big impact on how the earth formed as well, because the moon creates all these tides and it has its own gravity pulling on the earth.

SPEAKER_04 10:18

Yes. Definitely one of the very unique moons and satellites in the solar system, the Earth moon.

SPEAKER_05 10:25

Yeah, yeah. And then we get the early formation of atmosphere. So before the Earth was just open, bare to all radiation, and therefore no life. Life was very hard to preserve because it was like radiated away almost instantly. Um but the formation of an atmosphere of this blanket around the earth also made it more hospitable, both radiation-wise and temperature-wise, because you get the start of the greenhouse effect, the whole cushioning of the system from outer effects. So around this time, we already know and found the oldest fossil cells, which are about 3.5 billion years old, which is really old, especially if you consider that more complex life forms and actual visible, interesting life, I would say, forms only after 500 million years.

SPEAKER_04 11:14

But also like how fast, you know, like 4.6 the planet just forms. Then you have this period of cooling down, but boom, 3.5, we already have bacteria, right? So it's like it's not a long time for the evolution or like the appearing of life to happen. It's still a super very hostile environment, and then there was still like there were already bacteria.

SPEAKER_05 11:39

Yeah. For me, it's amazing. It's insane. It's insane. And so we find this oldest fossil, and there is many theories about how life formed on Earth. We still didn't figure it out. Another episode. Like there's too much.

SPEAKER_04 11:52

That's that's because that's something where I also geek out a lot about the panspermia.

SPEAKER_05 11:58

So in the book, they talk mostly about the theory that life formed around the volcanic middle ridges of the ocean, which is I think the least controversial and most accepted theory on how life formed. How that exactly works, complicated. We'll talk about it in another episode. And these cells were like single cells, nothing complicated, and it became more complicated around 2.1 billion years old when they started like ingesting each other and therefore using each other's abilities. And it sounds really gross, but yes, that really is how we think it happened. For example, you have a uh a cell that can do photosynthesis, you have a cell that cannot, so the one that cannot do it ingests the one that can and therefore has a new way of living or feeding itself. New feature unlocked. Yeah, yeah. It's sorry. It's literally like just just grabbing something like Pac-Man and then evolving bigger and bigger. Um yeah. As I said, very little of this era is preserved because of the plate tectonics being very little, the earth being still very hot to actually have large plates on Earth and very volatile, as I said. Then we enter the Proterozoic era, which is from 2.5 billion years ago to 541 million years ago. So we again take a large chunk of time.

SPEAKER_00 13:25

Yeah.

SPEAKER_05 13:27

But we get larger plates because the earth is cooling and they start congregating as well. So there are some supercontinents forming. Some names of these supercontinents are Nuna and Rhodinia, and the one the Rhodinia one you hear a lot in paleontology.

SPEAKER_04 13:42

Also, you hear this one. I would say if anyone remotely interested in Earth history, you would probably hear Rhodinia before. I have one question. Is it already because like I'm a totally noob in this, this, this sorry? Um of course, like we went through those courses during your university time, but like I diverged into very different environments. Is it already because like you say you have a large plates and then you have supercontinents? This also already implies we got water, we got oceans, right?

SPEAKER_05 14:10

Yeah, yeah, yeah. Oh, sorry. Oceans were always present, they were just quite hot in comparison to what we have today because of the active earth. Okay, the active volcanism, and yeah, okay. Yeah, yeah, yeah. Yeah, there were oceans, there's a a lot of water already. They were just warmer.

SPEAKER_04 14:27

Yeah, because you said that the earth, the sorry, that the life, the origin of life is kind of water-based, right? Because you have the hydrothermic thermal vents. And they were, but like for my understanding, they were more like ponds, but then you eventually you just create oceans, is it?

SPEAKER_05 14:43

Yeah. Yeah, yeah. It's um on Earth, it's usually either ground or water on the surface. So yeah, there would be very big oceans, but they would be a very different consistency, I think more silica-ish as well, because of the mixture of all these chemicals into the ocean, not solidified yet on the crust. Um, we'll talk about the contents of the uh ocean a little bit later. Let's see, we're starting at the Proterozoic, the pro Earth three modern times, I would say. We get larger plates because Earth is cooling, as I said. We have the supercontinents, atmospheric oxygen is also rising in this period, so we have more free oxygen on Earth to breathe or to, well, in this case, make certain iron formations solidify. So we get the banded iron formations in these times, but then the oxygen raises too much along this period of time, and therefore it rusts away basically. It oxidizes. It's oxidizes. Yeah. Yep. Yeah. So this is one of those important formations we found that made us led us to imply the oxygen content of the atmosphere, which we don't find today anymore. So it must have been very different from today. As I said, the life forms I call them lifeforms because I cannot call them like animals or bacteria anymore. It's like a little mix. I don't know, it has a strict definition, but I won't say I won't define it that definitely. I think I think lifeforms do a bit better. Um and they become more complex, but they are still very small. So you cannot see them with the naked eye, anything that lives, unless they clump together. So in this time period, we also get the first the earth is actually cooled down, so we get the first glaciers on Earth from 1.5 billion years ago to 541 million years ago. Um, and we find ice on very low latitudes, like around the equator is even caverns of ice, of this freezing and cooling structure of ice age. Um, so somehow ice became or freezing temperatures came very close to the equator, which causes all kinds of effects, right? The like we will talk about this in a in a climate episode, but that the snow reflects the albedo. Yeah, the albedo effect. So it reflects the sun, therefore it gets colder. There are all these feedback loops that make it colder. It is there for like a dermino effect. Yeah, yeah, yeah. Exactly. This is positive feedback loops, it keeps making itself bigger. So there's this theory that there was snowball Earth around this time, so the Earth covered froze itself. Yeah.

SPEAKER_04 17:22

Does it also correlate with like, you know, I guess it's very early on in the development of like also planet, maybe like instability of the planet's uh orbit, or it's just purely because of the climate of the Earth.

SPEAKER_05 17:38

Yeah, it's not mostly the climate, yes. Because I think at billion to five hundred billion years ago it was already pretty stable. The the shape of Earth, the the temperatures becoming more stable than before. Yeah. But it's not it's one of those theories that is like, do we really believe it? There needs to be more research. There always needs to be more research, it's always the answer. But it's one of the most debated ones on between scientists because they cannot agree if it really ever happened, how it happened, how we got out of it as well. Because somehow snow earth stopped existing, otherwise we would have snow.

SPEAKER_03 18:14

Yeah, exactly.

SPEAKER_05 18:16

But it does tell us that it'll cool down enough for climate to take its grip on how the earth is shaped. And the Precambrian or the Proterozoic, it's uh interchangeable name, um, ends with an explosion of animal life. So we get these complex creatures looking like animals that are becoming bigger and more complex. And it is thought that this is due to the availability of oxygen in the atmosphere and the oceans.

SPEAKER_04 18:42

So the more oxygen available, the more complex the life.

SPEAKER_05 18:46

Yeah, yeah. Yeah, we see it now as well for like animal forms that oxygen is it's always a limiting factor because you need to breathe in order to burn energy.

SPEAKER_04 18:57

It's pretty, pretty, pretty, pretty hard to exist without breathing.

SPEAKER_05 19:02

Yeah. For plants it's the other way around. We need to pump CO2 in the up in the air. For the animals, it's like Yeah, yeah, we will poison ourselves. Anyway, we enter the Paleozoic era. Um, and you can see we're making smaller steps in time now because there's so much more to tell in these steps because we know more, there's more evidence of different things, and so you'll see we'll start to make smaller steps, and we're gonna talk about the Paleozoic, so the old time, which is from 551 million years ago to 252 million years ago. Um, and it's seen as the start of more complex life on Earth. So we see mostly marine life exploding around this time, uh, and mostly species without spine, so invertebrates.

SPEAKER_04 19:51

I have a question because, like you said, mostly we see it complex life in a marine environment, but isn't it kind of biased by the record we have? Because, like, because of the plate tectonics, we don't have the record of like continental record, let's say, and the marine life anyway tends to be preserved much better. Like you mentioned in the second episode where we were talking about fossils, that the marine life is easier because the conditions of preservation are better.

SPEAKER_05 20:22

Very true, very true.

SPEAKER_04 20:23

So maybe there was a life outside, you know, like I'm right now speculating, I have no idea. Yeah. But we just don't see it because we are limited by the factor of what we can find the arc like archaeological paleontological record.

SPEAKER_05 20:38

Yeah, yeah, very true. I see where you're coming from. It is thought though that uh at this point there was not yet life on terrestrial, so on Earth above sea level, because the conditions there, even though we have this atmosphere and we have better climate, was still very harsh because there's no shelter from erosion, because there are no roots or or plants yet.

SPEAKER_04 21:00

There's no there's no shelter.

SPEAKER_05 21:01

There's no flow. There's no shelter, but there's no water because the life forms we're talking about right now, we're not even close to amphibians yet. So they're all very dependent still on water for procreation, for survival, for shelter as well. So I think we'll we'll get there, we'll get the evolution of plants on earth and then the animals following, basically, because there is opportunity created. But I think we're not there yet at this point in time. Yeah, it's still too hostile, I would say. So the Paleozoic is divided into a few subparts, and we'll talk about those one by one. And I think you're gonna I think you're gonna recognize some of these names because these are the ones we use more often, and the Paleozoic is the first era we talk about more as well. So we started the Cambrian, um, which is 541 to 485 million years ago, and at this point in time the sea level rise. Because of this ice that melts, right? After the snowball earth, all this ice and snow melts, sea level rises, oceans go from um aragonitic to calcitic, which means it's just the component that is dissolved most in the earth. And if it's dissolved more, if it's more present, these uh shell-making creatures are easily more easily preserved, right? Because they don't dissolve, because this compound is um more present. And why this is important is because calcite is way more resistant than aragonite. Aragonite's a bit more soft, so the shells we find today as well are mostly calcitic. We see also that animals start to radiate and become larger and more complex. And when I talk about radiate, I mean there is it's it's a scientific term for becoming more diverse, more abundant, more present, basically. So it's it's a radiation or uh expansion of animals here. We see the first skeletons appear with a variety of teeth and tubes. So we get these hard parts, these calcitic parts in life, which give other advantages. And we see that uh this era is dominated by trilobites. And it's I it we already talked about this mug many times, but it's one I need to mention. Again, it's uh the mug from Paleotyme NL, which my boyfriend is one of the organizers from, and says I'm a trilobit of a nerd, so if you ever get the chance to get this mug, please do, and think about the Cambrian where trilobites were very abundant.

SPEAKER_04 23:37

And these are for for the listeners, trilobots who don't who don't know. These are the crickets kind of like looking like cockroaches, right?

SPEAKER_05 23:46

Yeah, yeah. They're called the cockroaches of ancient time, yes.

SPEAKER_04 23:50

Exactly. So you will see them very often in this the pictures of Cambrian life when they just like crawl on the bottom of the ocean floor. You can buy them on like mineralogical exhibitions and stuff, they're quite popular there.

SPEAKER_05 24:05

Yeah, and because of all the hard parts, because they have all exoskeleton, just like cockroaches, for example, um, they are more easily preserved as well. Yeah. Um in this area era you also find the first vertebrates, so signed creatures or yeah, um, creatures with skeletons and larger invertebrate predators, so without hard parts.

SPEAKER_04 24:30

These are softies.

SPEAKER_05 24:32

Yeah, yeah, softies that actually start eating other softies. We end the Cambrian with a mass extinction of trilobites, which is a defining factor of this era. So we start with irradiation of life on Earth, we end it with a mass extinction, which happens often.

SPEAKER_04 24:47

Can you tell me like what is a mass extinction? Because that sounds like everyone died.

SPEAKER_05 24:51

Yeah, it depends on how you look at it and what scale you pick. Of course, you'll see later in time we have mass extinctions only in the ocean, so a lot of ocean life dying because of yeah, factors impacting the ocean, becoming less oxygenated, for example. We have mass extinctions on Earth, and I think I would have to look up the definition. Yeah, I wasn't sure about the percentage. So we will it is defined as a rapid and widespread decrease in Earth biodiversity, so species dying out, many different, and it like decrease has to be 75% or more. So the extinction has to be 75% or more species lost in less than two million.

SPEAKER_04 25:33

75% of biodiversity gone within how many years? Two million years. Two million years, that's very short time for geological skill, right? So it has to be really rapid change in the environment. Do we know why the Cambrian mass extinction happened?

SPEAKER_05 25:50

Probably a lack of oxygen in the ocean. So it is thought that oxygen declined rapidly, and there are many triggering factors for this, like tectonic shifts in the ocean and therefore creating a lot of a lot of oxygen uh sinks, mountain building, ocean stratification because of climate change, and therefore no mixing of oxygen in the ocean. There are many explanations which it's hard to choose from, I would say.

SPEAKER_04 26:14

So they're competitive theories, but there's no like one definitive answer why the decline of oxygen in the ocean caused the mass extinction.

SPEAKER_05 26:24

No, and probably that they went hand in hand.

SPEAKER_04 26:26

Hand in hand, okay, so like build-up effect.

SPEAKER_05 26:28

Yeah, like the one causes the other as well, because if you have a very active volcano creating less oxygen in the ocean, it also changes the climate, which in case can have an effect on ocean currents, which can have an effect on stratification. So usually it's not just one thing. Okay. It works together as a complex system, Earth is, right? Yeah, makes sense. So we end the Cambrian with a mass extinction and we enter the Artovician, which is uh 485 million years ago to 443 million years ago. Um, and we get to see more uh creatures like we know now. So we see some fish without jaws still, so the jawless fish, which uh how does it even look like? Uh yeah, how does it even look like? We'll have to post this on social media.

SPEAKER_04 27:18

Yeah, I'm just gonna look it up now.

SPEAKER_05 27:20

Yeah. It looks weird. It's it's like your I don't want to say this. It's like your grandma with i in fish form.

SPEAKER_04 27:25

Oh my god.

SPEAKER_05 27:26

Yeah.

SPEAKER_04 27:27

Okay, it looks like the teethless. It looks hilarious. Like we really have to post it on socials.

SPEAKER_05 27:34

Guys, it I think I think you have the hackfish or the lamprey in front of you, right?

SPEAKER_04 27:41

I put ordovician I put ortovician period jawless fish. And it looks bizarre. It looks always surprised.

SPEAKER_05 27:49

It goes like oh Yeah, there are many types of fish. We have the hagfish as well.

SPEAKER_04 27:52

I have like Arandas Peace, Arandas.

SPEAKER_05 27:56

Ah, yeah, yeah, yeah.

SPEAKER_04 27:57

Yeah. So it just looks surprised.

SPEAKER_05 28:00

Yeah. Yeah. So this is um the the jawless fish is a big um group in the Ordovician. Um, we also see coral reefs expand in the ocean. Um which creates a whole new environment for species to inhabit, right? This is also the first time where we find spores of earliest turns. Then the invertebrate fauna also starts to first fight, so the ones without the spine, like corals, all kinds of shell creatures, the echinoderms, so the urchins. Urchins, yes, that's a word. We we call them in Dutch sea hedgehogs. Sea hedgehogs. So I was trying to find this word, but it doesn't exist. It is not a thing in English. Urchins, sea urchins. It's not even close. But they look like hedgehogs, so to be fair, they have these these they they definitely do.

SPEAKER_04 28:52

But it's also, isn't it like the sea cucumbers? Are they also there?

SPEAKER_05 28:59

No, the the sea lilies.

SPEAKER_04 29:01

Ah, sea lilies.

SPEAKER_05 29:02

Yeah, it's these shell type animals like the the similar to what we now see are mussels, for example. They eat a lot of plants or the plankton, the plant material in the ocean, which is what stromatolites are mostly made of. And stromatolites are these these like spongy, wavy structures of plant material that were very common in ancient life or in ancient time, but because of the extensive grazing from these shell-like creatures and burrowing into the structures, stromatolites decline fast. We still see them today, I think, but not often. They're very rare. At the end of the Artovision, we have two mass extinctions again. It's it's like a recurring theme on our these mass extinctions. We usually define uh the biggest six, not the biggest five, and it is thought we are in the sixth one right now. But we'll talk about that later when we get there. But these are two like tiny mass extinctions. There's no way you can talk about a tiny mass extinction, but less recognized, right? First one of the warm adapted species, and then the second one of the cold adapted species. At the end of the ordovician, we also find the first signs of continental glaciation, which is an interesting shift from only oceans freezing over to continents freezing.

SPEAKER_04 30:29

Because you also mentioned about the glaciers on Earth, the ice, right? But that was the Proterozoic. So where was the glaciers?

SPEAKER_05 30:39

Yes, it was sea ice mostly.

SPEAKER_04 30:41

Sea ice, okay. So is it the okay. It's like icebergs.

SPEAKER_05 30:45

Yeah, yeah, exactly. Or at least that's how we interpret it. It could also be that there was continental glaciation and we just don't find these continents anymore with the scrapes on it.

SPEAKER_02 30:54

Okay. We have to limited record. Yeah.

SPEAKER_05 30:58

Yeah. Yeah, yeah. Yeah. There's always a chance there were already continental glaciers, then we don't find them anymore. We enter the Silurian period.

SPEAKER_04 31:08

I remember, because I was always forgetting about it.

SPEAKER_05 31:11

It's the the in-between, right?

SPEAKER_04 31:13

It's just the name is so forgettable. And then like when we had to have an exam when we were going through all the geological time periods, I was like, what was what was after Ordovian, before Devonian?

SPEAKER_05 31:28

Where is it?

SPEAKER_00 31:28

Silurian.

SPEAKER_05 31:29

Yeah, Silurian. So in this time period, it it extends till 419 million years ago, 443 to 490. Um, we see the shell type structures, snails, yeah, ammonite kind of things, like the nautiloids radiate again, and also trilobites, they have a whole new era. Yeah, they didn't die out, they just had a mass extinction. Okay. And also extinct.

SPEAKER_04 31:59

Yeah. Uh my my friend that we really need to get on this podcast, shout out to Alex Clark. He loves snails. So, like, we can just make him talk about snails for the whole episode. So, probably he right now hates me when I said, like, oh yeah, I totally forgot about the Silurian era.

SPEAKER_05 32:17

Important period for him. But yeah. It's like this is snail period. Uh, there's just too much to talk about for for it to be extensive about snails. But we'll we'll we'll talk to him about it all. So you can imagine after this glaciation period in the Ordovician, we now have rapid sea level rise because of the melt of all this happening. So the sea level rises again, which creates all new environments to get into. We also see the first land plants form, which is a very important evolutionary step, both for plants and their structures and for the opportunities and habitats on Earth that could be inhabited.

SPEAKER_04 33:00

You're getting tired to see that. I'm really trying.

SPEAKER_05 33:04

We can do this. Okay.

SPEAKER_04 33:05

We can do this.

SPEAKER_05 33:06

I wrote down a lot, so it's helpful, it's helpful. And these first plant species were like the horse tails we have now, so no vascular system to transfer water through the plant. They barely had any roots because it you don't need many roots in the ocean, like the seaweed just floats, right? Or it it attaches to a rock. It's not it doesn't have roots to grow moisture or grow into soil, and it didn't have leaves yet.

SPEAKER_04 33:31

Yeah, this is this is apparently like I went to the con you know, one of the conferences I went, I usually pick one day when I go random sessions, and then I somehow ventured into the session of paliva people, I guess. Sorry if I offended anyone. And they were having this heated debate about leaves, and I was like, man. Yeah, you know, the leaves are super important because of teeth and then seeds and whatever. Like that was a whole different universe for me. I was amazed that it's still geology, but they were debating about timing of leaves and importance of seeds.

SPEAKER_05 34:07

Yeah, yeah. Um I uh I think it's paleontology, paleobiology, paleobotany, however you would call it. Mix of these things. Yeah. So they were very primitive species still, with no paleontologists, just the plants. True, true. Good one. Then following the first land plants, there uh they formed enough shade and respite from the elements and less erosion, so critters could follow. So the the arthropods, which is a very generic group of animals and combine the scorpions, the spiders, and the insects.

SPEAKER_04 34:45

The insects were bloody fast, and they're gonna be the bloody last.

SPEAKER_05 34:49

Yeah, they're pests, right? Even then.

SPEAKER_04 34:52

It's just like imagine those I I I also heard that because of the oxygen that they could green grow quite big. Is that true?

SPEAKER_05 35:00

Yeah, we'll get there.

SPEAKER_04 35:01

Okay.

SPEAKER_05 35:02

Yeah, it's the Carboniferous and it's later in time. But they get like huge. We have um dragonflies of two meters wingspan.

unknown 35:10

Yeah.

SPEAKER_04 35:11

Okay, um Disclaimer, I love I love SmackBooks. So when you tell me wingspan, the only thing I hear in my head is like aquatar. And I'm making a promise to our listeners, I'm gonna be even more unhinged because I really want to make an episode about geology of like Prythian. Yeah. Okay, so no wingspan references, please T Cadawise. Gonna get cancelled.

SPEAKER_05 35:39

Okay, we'll get to the size of insects later, right? Insects, the size of insects. Um, still in Silurian. So we have these first land plants, we have these first critters on Earth, but plants do not get far into the continents yet because we still do not have these root systems, these vascular systems to travel or water to travel from far away into the plant. So it's all still close to sea in wet environments. This time we also see the first births without eggs in animals, which is an interesting shift because the egg was one of the first basic things after cell division.

SPEAKER_04 36:18

So what was the egg or the chicken?

SPEAKER_05 36:21

Yeah, I would say egg.

SPEAKER_04 36:24

I mean the chickens came way later, so I guess it was egg.

SPEAKER_05 36:27

Yeah, yeah. In Paleo, if you ask Pale pupil, it's always egg.

SPEAKER_04 36:31

Okay, good. Then we can always like market it as the episode. In this episode, you're gonna find out what was fast, the egg or the chick.

SPEAKER_05 36:39

At the end of the Silurian, we have another sea level drop, um, and we see the first straw of fish. So the first ones with teeth as well. And they expand to freshwater habitats as well.

SPEAKER_04 36:49

So right now what you're saying is that we have degradation between sweet water and salt water, right? And was it also created just because of we start having ice and then it was the reservoir for freshwater, and then this is reservoir, you know, the ocean is just generally reservoir of salt water.

SPEAKER_05 37:06

Yeah. Um I didn't read specifically into that. I'm guessing that's the reason, yeah. Yeah, for it ice to melt, the rivers to form, uh lakes to form, or these uh estuary type situations, delta. Yeah. Okay. They could move from salt to freshwater habitats. The same for molluscs or uh shell-like creatures, must. We entered the Devonian period, which is for 19 to 359 million years ago, and we see the first aminoids, so the ammonite family.

SPEAKER_04 37:38

Which I guess is also like a landmark of paleontology. I think if I think paleontology, I think like trulobites and ammonites, you know.

SPEAKER_05 37:46

Yeah, yeah, those are the ones that are most easily found, most widespread, easily preserved as well. So yeah, you see it a lot. If you if you go to south of England, you see them everywhere. It's really nice. They're very nice ones. Um, they first were straight, like just tubes of shells, and they become curled later on. So the more curled, the older the newer it is, probably. Generally. It's very generally speaking. The jawed fishes start to radiate, and we have sharks now, which means there's a lot of predation from these jawed fishes, right? This is also the time we see the first fish with lungs, which creates a hole new. Okay.

SPEAKER_04 38:30

That's huge.

SPEAKER_05 38:32

Uh, there's actually still a group living today, the lung fishes.

SPEAKER_04 38:35

Huh. I wanna see how they look like. Where is my mouth? I have too many screens.

SPEAKER_05 38:40

Yeah, so it's actually they still call it lungfish. They look just like fish, so they breathe a little bit differently than with the nor fish we know today.

SPEAKER_04 38:49

And they are fresh water, apparently.

SPEAKER_05 38:51

Yeah. So you can imagine this being a step towards like these life forms on land. Because this gets closer to amphibians already.

SPEAKER_04 39:00

Yeah. It kind of looks like, you know, this I know shit about fish also in English or in Polish, so both languages I'm dumb. But um it looks like this fish which is like at the bottom of lakes, and then it also has this like fins, which kind of could look like hands and toes, you know. Yeah, yeah, yeah. So it's slowly getting there. But they also look terrifying. I I'm scared of fish. So if I would see it in the lake, I would be like, nope.

SPEAKER_05 39:28

I I always find them so alien-like. They look scary for somehow.

SPEAKER_04 39:32

They look scary, and also I think it's fish are just scary because they don't blink, you know? They don't blink and creepy.

SPEAKER_05 39:41

They're so squishy and soft, but not soft at the same time. I know. Yeah, no, technically. Fish is not my favorite thing.

SPEAKER_04 39:47

No, no, no. Fish is you know, yum in the fish burger, but nah, in nature.

SPEAKER_05 39:52

So we have these lung fishes starting to show up in the fossil record, uh, radiation of the jawed fishes and sharks. And then on land we start to see more complex plant forms such as trees and forests.

SPEAKER_04 40:06

Wow. Also So finally the leaf people are like, yeah, Devonian.

SPEAKER_05 40:11

Yeah, stuff's happening at the Devonian. It's it's actually depicted mostly for its forests in paleo art as well. Um, and it has one advantage here because uh this is also the time where the first seeds start to evolve. So spores need a lot of water to transport and also grow into a plant. But the seed plants they are a package of food that is transported with the plant. Um with the seed. So therefore, it has a lot of advantage on expanding into land and being um less dependent on water.

SPEAKER_04 40:48

And also like it probably can cover longer distances, right? Because if you can create spores, there's more opportunity for it to get carried by the wind, carried with the river, it can like spread a bit more.

SPEAKER_05 41:02

Yeah, yeah. Seeds have a huge advantage over spores in this time. Um sorry, seeds. That was me. Seeds on the spores. Yeah. We also see continents that start colliding with each other, causing orogenies or the formation of mountains. We also see the first vertebrates on land, so the first spined creatures going into land because the tree, the trees provide shade for these types of animals, so the land becomes accessible to them. Because you can imagine like a very slimy, slimmery amphibian type animal going into full sun.

SPEAKER_04 41:38

Yeah, it would dry out, KO. Game over.

SPEAKER_05 41:41

So these shade, these trees provide shade, therefore opening up land for these types of animals as well. Um because like insects don't have this problem, they have this outer skeleton. Yeah. Protects them. Protects them, keeps the moisture inside. Because of the evolution of the jawed fishes, we also see the evolution of ostrachoderms in the Devonian, which is fish with an outer armor skeleton.

SPEAKER_04 42:07

What does it even look like? You tell me so many weird shit that I always want to look look up, and then I'm gonna have nightmares. Yeah, it's it's like cockroach fishes. These ones, okay, yeah. They look like frying pun but swimming.

SPEAKER_05 42:23

Yeah. Yeah, so they develop armor to protect themselves. I mean, I'm saying this wrong because evolution has no like direction. So they do not evolve to protect themselves. It's just the ones that have this armor survive more appropriate, more therefore proliferate. But you get the gist of what I'm saying. Yeah, I guess. We'll do these misconceptions later. Then we talk about evolution. Just know I understand how evolution works.

SPEAKER_00 42:49

I'm just sorting myself a bit where you're simplifying things. At the end of the Devonian, we have the proper amphibians.

SPEAKER_05 43:00

So first we had these critters going onto land, but this these are proper amphibians that can shift between water and land, and further collision of continents, causing more mountains to form. And the climate becomes colder because of the forests. The trees form roots, so the the soil is more broken up, and therefore we have a little bit more weathering in this time period. Also because the forest CO2 is taking out of the atmosphere, therefore decreasing the greenhouse effect and the earth becoming cooler, basically. We still find a lot of salt like deposits in this area because it's still dry on Earth. Forest starts to form, which contains moisture as well, but they're not widespread yet. So we still see a lot of dry areas at these deposits. Two more to go. Two more to go to handle it.

SPEAKER_03 43:48

Yes.

SPEAKER_05 43:48

Okay, good. We get to the Carboniferous, which has a very interesting name because it's what what you see is what you get. A lot of carbon. So it's um 359 to 299 million years ago. We see a lot of climate. Climate change, a lot of coal formations, coal swamps form because of the increase of plant mass. So we have these forests that break down and these swamps start to form. Um, an interesting change is that the seas change to aragonitic seas again, therefore shells becoming less preserved. Yeah, less preserved, softer as well. Um, and continents start drifting closer and closer together, which means that reefs become more abundant because we have many more warm inland shallow seas. As the oceans start to become smaller in between the continents because the continents move together, it also gets more shallow. And more shallow is warmer because there's more sunshine in there, which causes carbon deposition of the reef structures that live there. Um, amphibians start to radiate on Earth because of a lack of competition and predation, because they are still the only ones there big enough. The first ones there as well. Um and at the end of the Carboniferous reptiles start to be present there as well. So they the move from amphibians that are semi-aquatic still to reptiles becoming fully terrestrial. And the giant insects, as you saw, as you said, swarm the earth because of the high concentration of atmospheric oxygen, they could be bigger.

SPEAKER_04 45:12

More insects we get bigger.

SPEAKER_05 45:15

Yeah, because oxygen in insects is limited to atmospheric concentration because they don't have a blood system, same as we do. So the amphibians were still dependent on water for reproduction. We see the same with spores if we compare it to plants, but they still need water for their eggs and their offspring. In the meantime, reptiles started creating creating amniotic eggs. We've made the shift from semi-aquatic to terrestrial possible so they could move farther into Earth. We also see the evolution of gymnosperms.

SPEAKER_03 45:45

Oh my god, again, funny word. I'm gonna Google it and see how it looks like.

SPEAKER_05 45:49

I was gonna explain.

SPEAKER_03 45:51

Sorry.

SPEAKER_05 45:52

So a gymnosperm in it basically means a naked seed. So a seed without a microvisional thinker, I see.

SPEAKER_04 45:59

Oh man, I'm such a child sometimes. But yeah.

SPEAKER_05 46:02

But we all know a naked seeded tree. It's a Christmas tree, for example. These spine cones are the naked seeds where these seeds actually come out. Later we see the covered seeds, and then you would talk about an apple, for example.

SPEAKER_02 46:15

Yeah.

SPEAKER_05 46:16

So they have spine cone-like structures, and they become widespread in the Permian. So in this time period. Sorry. Widespread in the Permian, which is the next period we're talking about. In the mid-carboniferous, we have a large spread of ice gaps, also close to the equator again. Um, and we know this because of the layers of rock from that era, from that location, had cracks because of a freezing thawing cycle. So you see that days of they make very specific structures in the rock.

SPEAKER_04 46:42

You can also see it nowadays.

SPEAKER_05 46:44

So the continents are drier because of the ice gaps, because of the climate changing, less weathering, therefore more atmospheric CO2 present, which ends the ice age again. Classic feedback loop.

SPEAKER_04 46:57

So in the carbofinish uh so like right, you said that you have the coal and the swamps and a lot of oxygen and like this very rich flora, and then you start creating ice caps, so you you went through small ice age. Yeah. Is it happening at the same time or is it happening one after another?

SPEAKER_05 47:20

Yeah, it's in sequential. Okay, in sequence. Okay. Yeah. Yeah. And so we end with a dry continent, less weathering, more atmosphere, end of the ice age. And that's also the end. Yeah. And that's also the end of the Carboniferous. So we start the Permian with the end of an ice age, basically. That's the definition of the change. The Permian is from 299 to 252 million years ago. So really a small shot a little bit less than 50 million years. But it's an important era because especially because of its end. But it's also the last period we talk about in this episode. And it contains a further development of and spread of these naked-seeded trees, so the gymnosperms. Um, and we see the evolution of more complex vertebrates, so jaws and teeth evolve differently depending on the food source it fits. And we see that instead of swallowing prey whole, it's also possible to use these teeth on different food sources.

SPEAKER_04 48:16

It's funny because when I hear gymnosperms, I hear I see this like cone being a gym bro.

SPEAKER_05 48:22

We need to let AI make this image. It's good for social media. For social media. Ever seen gymnosperms?

SPEAKER_00 48:29

Where's my protein boy?

SPEAKER_05 48:31

Sounds gay. Oh my god. Yes, we do it. So they develop more, they spread more on Earth in the Permian period. In the last period of the Paleozoic. Um, in the late Permian, deep seas become more stagnant and depleted of oxygen because it's super warm. And when it's warm, we see that now on Earth as well, the ocean starts moving slower. Therefore, no oxygen mixes. The deep sea pump doesn't work anymore, which we will talk about in an ocean circulation episode later. Um, and the climate is warming and drying because of the formation of the supercontinent we all know quite well, I would say, which is Pangea. It's the one our current continent system is made from. Yeah, made from. Is that a good word?

SPEAKER_04 49:18

The developed from.

SPEAKER_05 49:20

Yeah. Yeah. Yeah. It's the it it's Pangaea that cracked apart and now forms northern Africa, southern Africa, the Americas, uh, Europe, everything. But in in the Permian, it all came together from some other continents and formed a supercontinent. Because of the large area, it became super dry. And because of this large land mass, no oceans, uh, sea levels drop.

SPEAKER_02 49:42

Yeah.

SPEAKER_05 49:43

We see a big difference between the air temperature between the equator and the poles, so we have a large contrast from equator to poles. And because of this dry period, we see a lot of salt depositions from this era. And the funny thing is, most salt we consume today is actually formed in the Permian. And I find it extremely funny when you have these like charts of the expiration date with an expiration date of tomorrow. Like it's 250 million years old. How is gonna be a lot of people?

SPEAKER_04 50:09

How is it gonna survive one more month?

SPEAKER_05 50:12

Yeah, yeah, yeah. Like a month on like million years skill. Yeah, but it expires, yeah. Sure. It's a mineral, it cannot expire. But okay. Um, in this period of time, we also see the first land mammals, but they're still very scarce, and they start to well also roam on Earth. And then in late Permian, we have the first therapsid, which are warm-blooded animals. So before we had the reptiles and amphibians, they were all cold-blooded um animals. But here we see the first warm-blooded animals. Um, there's a whole science on how to see if they're warm-blooded or cold-blooded. Um, I actually learned something about it using synchrotron data again. So I'm mentioning it again, I'm sorry. Synchrotron! But it has to do with bone density and structures and it it it's been a while since I dove into it, but um very interesting research as well to see from only bones, if it's warm-blooded or not. Uh in the middle of the perm, we have a mass extinction in most of the oceans, but at the end of the permian we have the largest mass extinction of all time. I think uh from the top of my head, 98 or 99% of species died out. Yeah.

SPEAKER_00 51:27

Largest extinction of all time.

SPEAKER_04 51:30

All time. Sorry, that was my impression of Canyon S.

SPEAKER_05 51:34

Nice, nice. Yeah. So at this point, many species went extinct, many species of corals, and it's called the end of an era. Basically, the end of the era of ancient life, the Paleozoic. And I think that's where we're ending the episode today because it's already been way too long. Um we arrived at 252 million years ago. Which you would say we have very little left, but there's so much more. Yeah.

SPEAKER_04 51:59

I think the closer the closer we are getting to the modern time, the more we have of a record and the more complex the life becomes because we saw that it developed from like Pac-Man swallowing cells to get different functions to literally start having land mammals and warm-blooded animals. Yeah, exactly. Which is crazy. I mean it's crazy. When you think about it, how long it's I think it's not even fathomable for human brain to understand this time chunks. Because, like, you know, how much humans changed over, you know, civilizations-wise, technology-wise, over two thousand years, six thousand years, eight thousand years, and that's just thousands, and we are talking millions and billions.

SPEAKER_05 52:54

That's a whole different skill to think on, which is the hardest thing to learn as a like aspiring geologist or paleontologist to see how these time skills interact and how how you can.

SPEAKER_04 53:05

I think there is also this part of cynicism. Like, you know, like some geologists I find very cynical because they're like, oh, you know, climate change, life on earth, been there since forever, it's gonna be there forever. You know, climate change, la la la. It was already the back then, different circulation of oxygen level and acidicity of the ocean. And I was like, but that's why we died, like mass extinctions, you know. This is why we have these things. I understand, dude, that you know, we as a life on earth we preserve, but I would like to preserve the human life, you know? Only because cockroaches are gonna survive doesn't mean that humans will survive. And like, sure, I appreciate that your knowledge about like a geological timescale, but it doesn't mean that humans operate on geological timescales. We are babies.

SPEAKER_05 54:03

We are very much alive now and not for millions of years.

SPEAKER_04 54:06

We are newborns, we just barely crawl out of the timescale.

SPEAKER_05 54:12

Yeah. Anatomically modern humans are only 55,000 years old.

SPEAKER_04 54:16

Yeah. So, like for for for the scale of being on on the earth, we literally mean nothing to what was before and what it's gonna be in the future. So maybe you know your ego should die down a little and focus on generally a good idea to dial down your ego. Yeah.

SPEAKER_05 54:36

Yeah. So I hope you enjoyed this walkthrough ancient time.

SPEAKER_04 54:40

It gives you a totally different perspective, which I think it's very important. Um, I like to, you know, like when I think about geological timescales, past life, uh, also about formation of planets and all the time scales, it just literally makes you feel very small, very it puts you in perspective. And I think certain type of people in in the planet, I'm not gonna name names, should think about it. And should think about what you know what you want from life because uh why are you a billionaire? Why are you hoarding this trillions and trillions of millions? For what?

SPEAKER_05 55:21

Yeah, yeah. You're so insignificant at the same time. You're in so impactful at the same time.

SPEAKER_04 55:26

Yeah. It's like, you know, like in a couple of hundred years, it's not even like million years, it's all gonna be gone. And like maybe you should think about impacting the current situation for everyone rather than hoarding whatever you have.

SPEAKER_05 55:42

My take. Definitely. I think this is where we're gonna end it. The next era we're gonna talk about is the dinosaur era, and um we're gonna get an expert on that because it's way more interesting than listening to me ramble about something that is not my expertise, even though a lot of people are interested in dinosaurs.

SPEAKER_04 56:00

We're gonna get for you guys, for you, my beloved listeners. We are gonna get you a dinosaur.

SPEAKER_05 56:07

But yeah, in due time.

SPEAKER_04 56:09

In due time. Stay with us.

SPEAKER_05 56:10

For now, this is it.

SPEAKER_04 56:12

Stay with us, stay alive, don't mass extinct, and do better. Do better. Always do better, always do better.