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Welcome to Science Pub, a monthly series, exploring the exciting scientific world around us.

I'm your host, Nancy Coddington, Director of Science Content for WSKG Public Media.

This season, we have a great lineup of speakers and topics ranging from mental health to exploring the science behind fire and firefighting.

Tonight's talk is "Ka-Boom!

Crash!

Shiver!

"How Paleontologists Are Unraveling "the Extinction That Killed the Dinosaurs."

Just like dinosaurs, countless ocean creatures went extinct under somewhat perplexing conditions when a giant meteorite struck the earth about 66 million years ago.

Yet excellent fossil records of their shell and remains help us to understand what happened ecologically.

Why did some organisms survive while others did not?

Doctors Myers and Pietsch lead a team of researchers investigating these mysteries using fossil records from the Gulf Coast.

Tonight we will hear about their research, why they became paleontologists, and how they came to study fossils from before and after the end of the Cretaceous extinction.

I'd like to introduce our guest tonight, Dr. Carlie Pietsch, uses knowledge of paleontology in geo sciences to advocate for the earth through teaching, science communication, and innovation.

She searches for common patterns of extinction and recovery in response to ancient extreme climate events to explain the processes that have repeatedly redirected the evolutionary path of life on earth.

Today, our ability to monitor and intervene in bio geo feedback loops carry implications for the progression of the sixth human induced mass extinction.

Carlie holds a BA in Ecology and Evolutionary Biology from Cornell University, and a PhD from the University of Southern California.

She has been an Assistant Professor in the Geology Department at San Jose State since 2017.

Welcome Dr. Pietsch.

- Thanks for having us.

- Dr. Corinne Myers is a paleobiologist working as an Assistant Professor at the University of New Mexico in the Department of Earth and Planetary Sciences.

Broadly, her work investigates the influence of environmental factors such as climate or sea level change versus biological factors such as competition or predation on patterns of macro evolution in marine invertebrates.

Her specialty is mollusks that live in a shallow ocean, covered the middle of North America 70 million years ago during the Cretaceous period.

Cori uses statistically modeling to hypothesis of survivorship in these critters on evolutionary timescale, particularly across major environmental changes such as the asteroid impact that wiped out the dinosaurs.

Welcome, Dr. Myers.

- Hello, thanks for having us.

- Thank you.

And you are both joining us from the west coast where I think the sun is still up, correct?

- Barely.

- Barely (laughing).

- It's dark, it's very dark here in Upstate New York.

Dr. Myers, do you wanna go ahead and start sharing your screen?

Dr. Pietsch and Dr. Myers are going to do their presentation this evening.

Please continue to ask questions in the chat, and we will get to those questions throughout the talk and also at the end.

- So, let me know when that is shared.

- Okay.

Ready.

- Thank you so much.

- Well, thanks, everybody for coming to hear Carlie and I talk about some of our research looking at the end of the Cretaceous when there was a giant asteroid impact, and we don't look at the dinosaurs particularly, but we do look at all the other marine invertebrates that kind of hung out in the ocean during that time.

So, I like to start off any discussion of mass extinction with making sure we're all on the same page when we talk about diversity and how diversity might go up or down.

So, we've had complex, very large bodied life since the Cambrian explosion, that was about 541 million years ago.

If you can see my cursor, this is a picture of what that earliest Cambrian fauna might've looked like.

I always tell people, if you're looking for aliens, you should really look back in the history of life on earth.

So, at this time we had a big increase in diversity, the number of things that were alive on earth, but also in disparity, which is the differences in shapes or morphology of what that life looked like.

And diversity then is something that we can measure as kind of the number of things that might exist on earth.

So, we might count species, we might count populations, we might count individuals, we might count groups of species and clades.

And we can count those things through the fossil record and up through today to get a sense of how much life has existed through time and what sort of wiggles and waggles and the amount of life there has been.

So, how do we make diversity?

Two ways, we add species by origination or speciation, and we subtract diversity through extinction.

And this talk, as you have I'm sure guessed by now, is going to be about the extinction parts.

One little segue.

It blew my mind when I finally learned that extinction was actually not an idea that existed in the way that scientists thought until the mid 1700s to early 1800s.

And that was originally codified and observed by this guy, Cuvier, who was a French naturalist and the father of paleontology.

And he studied vertebrate fossils, particularly things like giant ground sloths, mosasaurs, woolly rhinos, and mammoths, and really demonstrated that as opposed to the previous thinking that these were all just sort of modern animals that we hadn't found yet, he showed that actually these things are fundamentally different from the life that exists today.

And therefore demonstrate that this historical life has sort of left us by some kind of cataclysm or catastrophe.

Okay, so, if we're interested in looking at extinction, how do we actually recognize that it exists?

There are differences in scale.

So, if we are modern biologists, then we identify extinction as essentially not seeing any of the critters from that particular species for a really long time after we've looked for it a whole heck of a lot.

In the fossil record, we use stratigraphic data.

We go to fossil sections like this, and we look for the occurrence of a particular species.

This is an example of a compendium of the times during which different species survived.

And we can use these data then to make what's called spindle diagrams here, because they sort of look like the spindle on a spinning wheel.

And essentially, on the Y axis, you're looking at times.

So, you're going from that Cambrian explosion 541 million years ago up to the present in each of these columns.

And then the width of each of the spindles tells you how many things were in that particular group.

So, some of these groups might be clams, or they might be brachiopods, or they might be ammonites or species of dinosaurs.

So, you can see how the diversity of these different groups really waxes and wanes throughout the Phanerozoic, the last 540 million years or so.

And then we might wanna know why that is.

If you take all of those mostly marine critters and put them in one diagram, you get what's called the Sepkoski curve of marine biodiversity.

This is Jack Sepkoski up here with his adorable little dog.

He basically spent 15 years going through every paper that had ever been written about fossils in the Phanerozoic and made one of these plots at the family level.

So, groups of species, and then groups of those, he then spent another 10 years to bring this down to numbers of genera.

So, groups of species that are related to each other.

And if you just look at this in sort of a squinty eyed way, you can see that there are a lot of wiggles and waggles here, right?

Here's the Cambrian explosion.

We had this massive increase in diversity.

We had another one here in the early Ordovician, but then we had some pretty big drops of biodiversity through time.

And certainly, there is this sort of intriguing pattern of rapid increase diversity moving to the present.

So, this is 541 million years ago, and on the right hand side, the present.

Okay, so, using this data, we can start thinking about how extinction happens and at what rates.

And so, we identify two different types of extinction.

One is called background extinction.

And background extinction just describes the rate that species go extinct under sort of normal or average times.

Nothing wacky is happening.

No asteroids are hitting the earth.

What's the sort of average rate at which species go extinct?

In this paper down here on the bottom, Raup and Sepkoski put these things together and found out that our rate of background extinction is essentially somewhere between 5 and 15% of species that go extinct every million years.

And that's all of these little dots that are down here at the bottom.

But they also recognize then that there are several intervals here that are much higher in their extinction rates than this sort of average.

So, that's our average down there.

And several of them that are much higher in the rate of extinction.

And these are what we call mass extinction.

So, periods of time when we have very elevated levels of extinction, okay.

And not just very high extinction rates, but also relative to the number of things that we're adding, right?

So, if we want to make diversity go down, we can really subtract a lot by extinction.

We can also just turn down how many things that we produce by speciation.

So, this plot is showing you the big five mass extinctions that I'm gonna go through in just a second, that happened at the end-Ordovician, the end-Devonian, the end-Permian, the end-Triassic, and the end-Cretaceous, and approximately the number of things that went extinct at each of those time intervals.

The criteria then to be called a mass extinction is actually quite loose.

The definition basically says a lot of things over a short amount of time and a lot of places.

And we sort of apply that very abstract definition of mass extinction to say that essentially, you have to have about 70% or more of species that go extinct.

The extinction has to happen over a very short geological interval, typically less than 2 million years.

it needs to be global in extent.

So, it can't just affect North America, for example.

It needs to affect animals and plants all over the world, and it has to affect a variety of habitats.

So, we do a lot of work, Carlie and I looking at marine invertebrates, things like clams and marine snails.

And if it's only killing off things in the ocean, that still doesn't cut it as a mass extinction, it has to also affect things on land, things in deep ocean habitats, shallow, up mountains, down mountains, et cetera.

And finally, the recovery period has to be quite substantial.

So, if we think of a population today that gets covered over in lava, let's say, and everything dies, it actually takes about a hundred to 300 years before that population can actually grow back to the nice, beautiful forest that was there before.

With a mass extinction, that recovery period is millions of years.

Minimally, it is hundreds of thousands of years, and often it takes millions.

So, essentially we're talking about background extinction as something like this, this poor ichthysoaur is dead on the bottom of the ocean.

And it's just one ichthysoaur, and this ammonite might want to chew on him compared to something like this.

Obviously, when an asteroid hits the earth, that is a pretty catastrophic event that does a lot to change climate and the earth system, and then therefore can create high extinction rates.

Okay, so, what's the big 5?

In this little picture here on the top right, you're looking at geological time.

So, the very bottom is when the earth formed 4.6 billion years ago.

When you see this blue rectangle that says Paleozoic, that's the beginning of the Phanerozoic, so 541 million years ago, and then going all the way up to the present at the top where these geologists are excavating fossils.

Here in the big white box, you're looking at the amount of extinction that's happening again through time.

So, here's the Cambrian on the left, 541 million years ago.

And the edge of this is going to be the present.

So, our first mass extinction is the end-Ordovician.

This happened about 443 million years ago.

86% of things went extinct over a very short period of time.

These are things like trilobites, which I sort of think about as marine cockroaches, rugose corals, these are little solitary corals, and conodonts, which the mouth parts for funny little fishes that sort of look like hagfish.

And we think that this end-Ordovician mass extinction was actually triggered by rapid glaciation on the earth.

You have this pulse of things getting very cold and you killed everything off.

And then you had radiation of things that like the cold, and then it got warm again.

And all of those cold preferring animals then died off.

Okay, next, we have the end-Devonian, which happened about 359 million years ago.

About 75% of species went extinct.

Things like these brachiopods which look like clams, but they're a little different.

Things like stromatoporoids, which are a reef building sponge.

Things like placoderms, our first fish that had jaws, big, great predators, but their jaws were actually on the outside of their bodies with these weird plates.

Things like my favorite, the ammonites or ammonoids, and then more of our trilobite friends here.

And we think that the end-Devonian was actually caused by the emplacement of a large igneous province, which is basically a giant volcano that erupts for thousands to hundreds of thousands of years and outputs tons of lava, and also tons of greenhouse gases and other nasty gases into the atmosphere that can cause things like anoxia and acid rain.

Okay then, Permian is by far the worst of the extinctions that we can observe in the Phanerozoic.

It happened 252 million years or so ago.

And upwards of 90 to 96% of species went extinct.

So, that, let's take a minute to just really visualize what that means in your head, right?

Only 4% or so of all life made it through the end-Permian mass extinction.

So, some of these animals, fenestrae bryozoans, the sea scorpions, the eurypterids, trilobites go extinct completely forever, as well as these bizarre tabulate corals.

A lot of these things went extinct forever and never came back, but a lot of everything went extinct at this time and barely anything was left then to start the Mesozoic and actually rebuild diversity into something that's more similar to what we might see in ecosystems today.

We are pretty certain that the end-Permian was triggered by another large igneous province called the Siberian Traps that erupted across Siberia, 3 million cubic kilometers of lava over maybe a hundred to 200,000 years.

Okay, the end-Triassic is our fourth of the big five mass extinctions that happened about 200 million years ago, just after all the animals on the earth and plants were rebuilding themselves after the end-Permian, they got hit again with another mass extinction, 80% or so of things went extinct.

This ended up causing extinction in a lot of terrestrial reptiles, more brachiopods, the conodonts go extinct forever.

Sponges that were made out of calcite.

And then my poor ammonoids were hit pretty hard again also.

And then finally, the one we're gonna focus more on today is the end-Cretaceous.

That extinction occurred about 66 million years ago with about 76% extinction, most likely caused by an asteroid impact that hit in the Yucatan Peninsula.

My favorite bivalves, my favorite clams, the rudist, this guy is like an ice cream cone looking clam, went extincts at this time, all of my beautiful ammonites went extinct at this time and we actually lost all of the marine reptiles.

So, prior to the Cretaceous, the oceans were quite dangerous.

They weren't just filled with things that would eat you like sharks, but they were also filled with giant marine lizards in the form of mosasaurs here, or plesiosaurs here that would also eat you happily.

Okay, now, do we see these mass extinctions beyond the water, right?

Not just with marine data, and the answer is for the most part yes.

So, if this top left graph is showing us our marine invertebrates, the top right is showing you vascular plants, and you can see the end-Devonian mass extinction and the end-Permian mass extinction here.

If we're looking at non marine tetrapods, which is to say vertebrates that live on land and have four limbs, we can see the end-Permian, the end-Triassic, and the end-Cretaceous mass extinctions in those records.

And insects, we can also see the end-Triassic, sorry, the end-Permian, end-Triassic, and the end-Cretaceous.

So, these mass extinctions do in fact impact life beyond just in the ocean.

Okay, so, who cares?

Why are you coming to this lecture to sort of hear us talk about things that happened so many million years ago?

Well, I would argue that understanding how extinction happens and why it happens and what are the particulars of how extinction happens is important because a healthy and diverse biosphere actually provides us with goods and services that we need to survive.

So, extinction matters because it produces, or it affects the ability to have food, raw materials, textiles, building materials, plants, bring oxygen, or increase the oxygen in our atmosphere.

The biosphere actually moves nutrients around, and we also use things like plant material and algae for fuel.

And of course, fossil fuels, which are the fossilized remains of plants for the most part.

Okay.

The biosphere also provides us with medicines.

And a very large percentage of medicines are actually derived from natural products.

Plants are a particular common one, Medications for leukemia, for cancer, to combat inflammation and pain, often come from plants.

Animals also provide medicines for things like blood pressure regulation, thyroid, AIDS, and HIV treatments.

And again, pain.

I have this little cone snail down here, which you should never pick up on a beach and put anywhere near your head, because it has a little stinger that it will inject you with a neurotoxin and you will die very quickly.

However, upon studying this neurotoxin a little better, scientists have actually discovered that it may be a very useful and non-addictive pain reliever.

And pharmaceutical companies are working on that to this day.

And fungus, fungus is a great, great producer of medicines.

Almost all antibiotics are based out of fungal species and also things like cholesterol medications.

Okay.

And finally, the biosphere gives us quite a lot of services.

Plants regulate climate, waste is decomposed here by these cute little fungus mushrooms.

The biosphere provides pest control to help us to make our crops do better and clean our water and our air.

As an example down here on the right, mangroves actually clean nitrates and phosphates, which are often present in fertilizers out of the water, which makes the water able to host sort of the natural biota without being polluted.

And of course, we had no soil on the earth until plants moved up onto the land and they turned up the soil, which of course is how we get nutrients to do perform agriculture.

Okay, I would also argue as an academic, as a scientist, that extinction matters because every time an extinction occurs, we lose information about evolution.

99.9999999% of all things that have ever been alive are now extinct.

And so, if we want to understand the history of life over that 541 million years, then we really need to consider extinction.

So, as an example, this is a family tree or a phylogenetic tree of giraffes and okapis.

Here's the ancestor a really long time ago that evolved into okapis here on the left, and giraffes on the right.

And if we didn't actually study the fossil record and think about extinction, we would completely miss that there was this little group of half giraffe, half okapis that went extinct much earlier than what we find alive today.

Okay, and finally, finally, we need to understand extinction over geological timescales, because this is the laboratory for us to understand what types of conditions lead to large extinctions that might be important for how we think about what's happening on the earth today.

So, we are staring some amount of global warming in the face.

We're also staring down quite a bit of habitat landscape modification.

We are looking at about a million species facing extinction in the next several decades.

And we're really, we are really increasing extinction rates today about a thousand times faster than backgrounds.

So, this plot here on the right is showing you the number of species that have gone extinct since the sort of 15, 1600s to about 2010.

And there is this big uptick in extinction, kind of right around the Industrial Revolution.

And this has led some people to say, "Are we in the midst or are we about to begin "a sixth mass extinction?"

And I think it's important then for us to understand the history of extinction in order to answer that question appropriately.

- Dr. Myers, I have a question here.

What was included in the 4% of organisms that survived the Permian mass extinction?

- So, a lot of things.

So, a lot of things like brachiopods and clams made it through, more clams and brachiopods.

Ammonoids made it through, not all of them, but just a couple of them.

Same for some of our terrestrial tetrapods, or reptiles that kind of then lead in the Triassic and Jurassic into our dinosaurs.

So, the ancestors of dinosaurs kind of made it through.

Mammal-like reptiles made it through, which paved the way for mammals to evolve quite a bit later.

Carlie, what else made it through?

- Amphibians.

- Amphibians.

- Fish.

- Yes.

- Like representatives of each of those groups.

But very few of them, you can kind of think of like a, just a couple of species of each one making it across the boundary.

- Okay.

Cori, there's been also a request.

I don't know if your menu bar can disappear or not at the bottom of the screen.

- Oh, how about that?

- Perfect.

- Okay.

- Great.

So, now that we've had this awesome introduction to the context for mass extinctions and why people like Cori and I decide to study them, I'm gonna fill in some of the details about the end-Cretaceous mass extinction, what caused it, and why we are studying it.

So, this event occurred 66 million years ago and resulted in about 76% of all species on the planet becoming extinct.

And everybody, of course, knows this mass extinction as the one that killed the dinosaurs, as you can see on the screen.

But the first hint that we had as to what was the cause of this mass extinction actually came from chemistry that we can see in the rocks.

So, on the next slide, we have this idea that we didn't just kill the dinosaurs, we also lost things like the marine reptiles, pterosaurs, which are flying reptiles, the ammonites that Cori loves, lots of different kinds of plankton that were living in the ocean, and different coral and clam groups.

The foraminifera, yeah, that Cori circling there.

All of these different groups were also going extinct.

So, if you take away one thing from this talk today, it's that it's not just the dinosaurs, all these other important creatures also met their end.

And yeah, so, the most likely trigger is this impact event, which many people are familiar with, that there was an asteroid about 10 kilometers across that hit the earth 66 million years ago.

And the first piece of evidence came from two scientists, Walter and Louis Alvarez who were looking at iridium.

So, iridium is an element and we don't have a lot of it at the earth surface.

There's very little.

And they were actually interested in using iridium to study how rocks accumulate at the earth surface.

How long does it take for sedimentary rocks to get deposited?

And they were looking at different columns of rocks.

And here is a picture of a column of rock in Gubio, it's a town in Italy.

And as they were measuring the amount of iridium in the rock, they saw that there was a seven times increase in the amount of iridium.

So, that's indicated by the red dots on the graph in the bottom left.

There's very little iridium in the rock, and all of a sudden you see it jump up and then decrease.

And they had a question.

Where would all this iridium have come from?

Well, we don't tend to find it at the earth surface, so it must've come from outer space.

Well, what would have brought such a large amount of iridium suddenly to be at the earth surface?

The idea that they had here was that it would come from some kind of large impact event, because all of the iridium that would have been originally at the earth surface has now gone to the core.

So, there has to be an extra terrestrial reason for this spike in iridium.

But we didn't have a crater for a few years.

It took a little bit of time before people were able to find the actual impact site.

So, later in the 70s, some geologists who were looking for oil were using the Earth's gravity to look for places they might be able to sample oil deposits.

And what they discovered off the coast of Mexico on the Yucatan Peninsula was this weird circular anomaly, this round structure.

And they realized that this was the result of an impact crater.

So, the figure in the center shows you the idea that when an impact hits in the top frame, it results in the melting of the rock that is impacted as well as the melting and vaporization of the asteroid itself.

And then you can see ejecta spewing out from the sides of the crater.

Then you have sort of like when a drop of water, if you've ever seen a drop of water in slow motion.

You have a bunch of material that rebounds in the space where the impact occurred, and then you have the crater sort of filling back in, faulting back in to fill in this circular space.

So, this crater has now been extensively studied, the rocks have been sampled through drill ships, and we're able to know a lot more about how it formed.

But this was able to tie back to that iridium spike that change in the earth surface chemistry, to indicate that there was this extraterrestrial impact at the time that the dinosaurs and other creatures went extinct.

The other thing that's really important to realize is that after the impact, we have a huge vapor plume.

All of this vaporized rock, the asteroid itself is vaporized, goes up into the stratosphere and we're able to see a worldwide distribution of material that's been generated from this crater and is now redistributed around the earth.

That includes the iridium from the initial impact, as well as changes in sulfur and carbon content of the rocks that have moved all around the world.

So, on the next slide, we're able to see indicators at the center, the Gulf of Mexico, with red and orange and purple dots, and spread around the globe with the yellow dots, we're able to see examples of changes in the earth surface chemistry.

So, increases in iridium, and also changes in other chemical elements, things like sulfur and carbon, that were at the Yucatan Peninsula, but became vapor and got redistributed around the earth as those rocks were vaporized and sent up into the atmosphere.

So, we have shocked quartz, shocked quartz is a piece of quartz mineral, and it's been deformed.

So, you can see these lines that are running at angles to one another, which represents the pressure that these materials experienced when the impact occurred.

And then they get blasted into the atmosphere and redistributed all over the earth.

So, we can find them in rocks spread far away from the actual impact site.

We also see tektites and spherules.

So, these represent a really chemically and physically unique pieces of glass that have chemistry similar to the rocks that were at the Yucatan Peninsula, but have been melted, sent up into the atmosphere, and then redeposited as cool cold little balls of glass.

And we actually found some during our field work, which we'll talk about, these little circles that you see in the rock actually represent these little balls of glass that were from the impact and have been shot up into the atmosphere and then fell back to earth and deposited as rocks in the ocean.

And then the last piece of evidence we have for this asteroid impact are tsunami deposits.

Especially close to the impact crater, we see these really disturbed rock units that represent the tsunami wave that would have rushed out from the asteroid impacting the ocean in the Gulf of Mexico across the Atlantic and across the Gulf up into the present Gulf Coast today.

Okay.

- Dr. Pietsch, I have a question.

So, what was the approximate diameter of the crater?

- Oh, great question.

- About 200 kilometers is the diameter of the crater.

It's big.

- And yet so hard to find.

- And yet so hard to find.

- Cool, okay.

So, the question here is what actually killed 76% of life on earth?

It wasn't the asteroid itself.

Of course, anything that would have been nearby that impactor would have experienced vaporization, debris being ejected, the tsunami, and magnitude 11 earthquakes just totally off the charts.

But what really matters is what happened globally.

And that's what went into the atmosphere.

So, when we impacted the sulfur and carbon rich rocks at the Yucatan Peninsula, the vaporized sulfur goes up into the atmosphere and it actually blocks sunlight, which results in a cooler climate, and that disrupts photosynthesis.

So, we have less sunlight, and now we don't have the primary production, the plants that are the basis of the food chain.

All the carbon that gets added to the atmosphere causes there to be acid rain.

And that acid rain is killing plants on the earth surface and acidifying the shallow ocean.

So, any creatures that are living at the surface of the ocean are gonna experience that change in the ocean chemistry.

So, when we lose primary production, when we lose plants and the bottom of the food chain, all of the animals also suffer.

Anything that was living at the surface of the earth is experiencing these cooling temperature changes and anything that is stress intolerant is going to literally bite the dust, 'cause that's about all that's gonna be left.

There's been some really recent work that is doing modeling.

So, trying to experiment, let's take the way that our atmosphere moves and the way that our oceans move and add this volume of sulfur into the atmosphere to see how cold would it have actually gotten.

And what their studies show is that it would have been like a nuclear winter, about 26°C, which is an 85°F decrease in temperature.

So, imagine being at the beach, it's 85, you're sunning yourself, and suddenly it is literally 0°F below freezing.

That's what these animals would have been experiencing once all of that dust was distributed around the atmosphere.

This event happened quickly over about 10 years, which is geologically very fast.

And it took about 30 years before the climate came back to normal.

And then hundreds of thousands of years before the atmosphere, the ocean, the land surface, and all life started to return to the levels of diversity that were abundant before the event took place.

So, what we want to know when we're looking at ocean animals that lived during this time, we wanna be able to study animals from before and after the extinction and figure out which animals survived this event and which ones were able to recover following this mass extinction.

And we're really focused in on mollusks, which are the clams, the snails, the ammonoids, the animals that are living in the shallow ocean at this time.

And we wanna figure out how the available habitat impacts organism's ability to survive extinction.

If habitat is changing across this extinction boundary because of all those devastating consequences I just laid out for you, is that affecting organism's ability to survive the event and to thrive in the aftermath?

And so, we wanna document whether species are able to actually change.

Do the survivors that make it across the boundary, actually evolve new preferences for different habitats or different ways of making a living.

And then finally, we want to understand what other ways organisms may have changed in response to this event.

Did they change their body size?

Did they get smaller or larger in order to survive?

And did they change anything about their ecology, the ways that they eat or move around.

And so, we're gonna do this by looking at these different sites in Mississippi, Alabama, and Arkansas, which are indicated with these red stars.

And we have data from some additional sites, but why are we going to Mississippi, Alabama, and Arkansas?

Well, on this map, all the areas that are colored in yellow actually represent ancient ocean sediments.

So, during the Cretaceous, when this event occurred, sea level was higher and our modern coastline wasn't present.

Instead, the coastline was much farther inland, which is indicated by the blue line on the map.

And so, we can find rocks that were deposited at the bottom of the ocean far inland from where the ocean is today.

And so, all of our clams and snails and squid that were living in the ocean when they died, they settled to the bottom and we're able to collect them.

And the white line here actually indicates where our Cretaceous and Paleogene rocks occur.

So, yeah, go ahead.

So, you might kind of look at a map and think, "Wow, there's Cretaceous and Paleogene rocks everywhere."

But you can't just kind of walk around and find the rock.

We have to find places where it's exposed.

So, we find ourselves in riverbeds like the photo of myself and Cori here, along roadsides.

And in some other unusual places, looking for places where rocks are visible at the surface.

So, next time you're out for a drive and you see stacks of rocks as you drive along the road, you might wanna go back and look those up and see what time periods they represent, and figure out maybe there's some fossils in them.

So, for us, we're using the fossils themselves to figure out where we are in time.

So, in this picture, Cori and I are measuring the rocks so we can compare it to other scientists' works.

And we're looking for specific fossils, like ammonites that live for really short periods of time.

So, the colorful columns here represent stacks of ocean rock that have piled up over time.

And we wanna know how old these rocks are and figure out if they contain the end-Cretaceous mass extinction or not.

So, we're gonna go out and look for ammonoids.

So, if you click, one click will pop up a picture of this ammonoid.

This ammonoid is representing, it's called discursive by these conradae.

And it lived pretty far back in the Cretaceous.

And so, you'll see some red lines next to these columns, that represents the time that that ammonoid lived.

It tells us those rocks are too old.

They don't represent the mass extinction.

Now, there's an ammonoid on green, which represents discursive by these ammonoidea.

We're getting a little bit warmer.

We're getting closer to the boundary, all of these places where the rocks have a green line next to them are getting closer to the end-Cretaceous mass extinction.

And finally, we find the ammonoid discursive over these iris, this lived during the latest Cretaceous.

So, if we find this ammonoid, we know that we're getting really close to the end-Cretaceous mass extinction.

So, that's how we're using the fossils to tell time, these short-lived ammonoid groups.

So, we find ourselves in riverbeds, along roadsides, and other usual places looking for fossils.

So, here we are actually in a famous landfill in Mississippi, we're taking careful notes here on the details of the rocks so we can figure out where we are in time.

In the next slide, we climbed cliffs along creek beds, and we're taking samples every half meter.

So, you can see people in this photo taking samples from many levels of the cliff, so we can understand how the fossils were changing through time.

And finally, we were also sampling along some scenic roads in the countryside.

And you can see photos here of Cori and some of our students taking samples at various intervals.

So, when we take samples, we sometimes have to dig trenches because the rocks aren't exposed.

So, we dig holes in the ground to be able to find the rocks of the right age.

And we try to take samples of the same size, about a gallon of rocks and fossils.

And we wrap them carefully so we can transport them back home.

And it takes a really big team as sometimes we had up to 15 people actually in the field with us at any given time from many different institutions in order to be able to collect all these fossils, dig all the trenches, make all the observations.

And we had a really great time.

You can see some other photos of us getting quite dirty and all of our gear piled into the back of the van.

When it would rain, that'd be a great opportunity for us to clean off our gear and get a look at what we've been finding and also pack up some boxes.

So, we have some images of us shipping our samples.

It takes a lot of crumpled up newspaper to make sure that all of our fossils, which are really delicate, don't get banged up when we ship them back to our universities to study them.

And when we get them back, we fill a whole lab room with boxes and boxes of fossils that now we get to unpack and start to look at.

We use all sorts of different tools, things like hammers and chisels, microscopes, and even tiny little miniature jackhammers to remove the rock from around the fossils really carefully.

We use dental tools and other really tiny picks to carefully remove bits of clay and bits of sand to reveal all of our fossils so that we can identify them.

- [Cori] Okay, well, so how do we then use this information to really get at those four areas of science that we're particularly interested in?

Who survives?

Do they adapt?

How does their ecology change through time?

So, the first thing we try to do is look at survivorship.

And this includes looking at what types of animals survive and the traits, the ecological traits that they might have.

This particular site along a creek in Mississippi is extremely important because it not only includes surviving clams and surviving marine snails, but it also includes surviving ammonites, which the ammonites were supposed to go extinct at the end of the Cretaceous.

So, this is a very special site.

So, here's the end-Cretaceous mass extinction event in the red dotted line.

Above that is our tsunami deposit, we call that the event deposit.

Below this is Cretaceous chalk, and above this is Danian sediments and we've found several, I'm just showing you two spots, but we found several ammonites above this tsunami deposit, which suggests that maybe some of these ammonites are actually surviving for at least a little bit of time, maybe thousands, tens of thousands to a hundred thousand years after the impact.

We also use the fossils and the sediment that we find to try to reconstruct what the environment was like just before the mass extinction and then right after the mass extinction.

If we wanna know how species are changing in response to environmental change, we need to first know how the environment is changing.

So, we can do this geochemically using stable isotopes things like oxygen stable isotopes, carbon stable isotopes, strontium, and even sulfur.

And we sample little pieces of the calcite or carbonate shell on our marine critters, like our snails and our clams.

And then we can measure these elements and see what they can tell us about the environment.

So, for example, oxygen isotopes can tell us something about the temperature in this case.

We are right up in here.

There's all these little gray points are the data.

So, a ton of people have measured this, and the farther you go in the left direction is warmer, and the farther you go in the right direction is colder.

We also look at carbon isotopes and that tells us about the carbon cycle.

Are we burying a lot of carbon?

Do we have a lot of carbon moving through the atmosphere and the biosphere.

We can look at strontium isotopes here, that will show us or tell us something about continental weathering.

So, how, if there's a lot of weathering, our strontium ratios will be higher.

And then we can use sulfur isotopes.

Oh, I think I had, yeah.

Oh, carbon, strontium, okay.

And then we can look at sulfur isotopes as well, which will tell us about the sulfur cycle.

And we geochemists are actually now developing sulfur isotopes as a potential tool to try to understand where that sulfur is actually coming from.

Is it coming out of a volcano or is it coming from the rocks that were vaporized when the asteroid hit the Yucatan?

Okay, when we collect then all of this biological data of where species existed, and then this information about paleo environments, one of my jobs in this project then is to put these data into a statistical model called Ecological Niche Modeling.

And to try to get a sense for how species preferences and environment have changed over time.

So, what you're looking at here is a little map of where there are cone snails that live in the Caribbean, and behind that are environmental parameters.

You could think about this blue line as being changes in sea surface temperature.

Maybe this pink one is changes in sea surface salinity, and maybe this red one is oxygenation at the surface.

We can use Ecological Niche Modeling algorithms, so, different ways of doing these niche models, to essentially correlate where these species are with the combinations of environments that exist at those places.

And then the model says those are good because the species can live there.

The model then also samples other places where your species are not.

And those combinations of environments the model says are bad.

And so, what you get at the end of this exercise is a map that looks like this, the continents are in white.

Anything red is predicted to be good or suitable habitat for these species.

And anything in blue is predicted to be bad.

Okay?

So, this allows us then to say, what happens to this little cone snails' preferred environment on the other side of the mass extinction event?

Do all of these red spaces actually go away?

Is that the reason then that those little cone snails maybe when extinct?

Do the red areas actually expand?

Do the cone snails move into different areas?

That brings us to another type of ecological modeling that we can apply.

And this one is actually asking whether species can adapt to changing environmental conditions.

So, what we can do is we can run a niche model for say the Maastrichtian, let's say the Maastrichtian is in green here.

And we can look at where our scaffite exists within this environment right before the end-Cretaceous mass extinction.

And that's what this green blob might be.

And then we can look at this surviving scaffite right across the boundary in the early Danian, right after the end-Cretaceous mass extinction.

And maybe this is what the environment looks like at that time.

And then the red blob might be where our little scaffite is living at that end-Danian.

Importantly, these axes here are kind of summarizing different aspects of the environment.

So, for example, it could be sort of temperature and salinity space here.

Okay, so, then we can use a particular type of model, for example, the Ecospat model to test for overlap between the preferred environments of the same species through time.

So, if you have a lot of overlap, that's this blue area, then you can feel pretty good that that species is liking the same types of environments across this boundary.

So, they're showing a stable environmental preferences or niche.

If these were not overlapping, then that would suggest that this species is actually adapting to live in new environmental conditions across the boundary.

We can also apply this, not just to looking at a single species through time, but we can also ask, does this sort of offspring of this species or do this sister species show similarities as well?

- [Carlie] So, one of the other things we wanna do is to look at our fossils and say something about how they were living.

So, in order to model their ecology, we have to have an understanding of how they behaved in the past.

So, we might have the idea that Tyrannosaurus rex was a carnivore because of the teeth that it has in its jaw.

So, we can also look at clams and snails and squid, and look at what we know about modern representatives of similar groups, and figure out how were animals moving?

Were they really mobile and were crawling all over the place, or swimming all over the place.

Or were they stationary like these mussels, which you may have seen out adhered to the rocks in a tide pool.

Were they buried into the sediment?

Which is a word we use to describe that infaunal.

Or were they living out on the surface like this snail, which is epifaunal.

Or again, are they kind of gluing themselves to the rock, like an oyster or a mussel?

The other thing we're really interested in is what were they eating?

Were they eating other animals?

So, where they carnivores, like these snails are actually carnivores.

Were they grabbing food from the water column, we call that suspension feeding, or were they sifting through the mud of the sea floor, which we call deposit feeding.

Some of them even use chemosymbiosis.

So, they have organisms living inside of their shells that are actually doing chemical reactions that produce food for them.

So, we can look at those changes across the boundary and the amount of feeding types and mobility types to understand how those niches may have changed in response to this mass extinction.

So, we're able to put together information from the geology, the paleontology, the evolution, and ecology, the chemistry and the statistical models, all to get a really better and complex picture of how the end-Cretaceous mass extinction was actually taking place, and how life recovered from this catastrophic event.

And that's all we really wanna understand.

We wanna understand if we're causing an extinction today, what is that recovery gonna be like?

And what could we be doing to maybe help life return from a mass extinction event?

So, this is a clue for how species and ecosystems are gonna respond to the really rapid environmental change we have today, and give us an idea of which things might make it across the boundary in the future.

And I think at this point, maybe we'll take any questions that you all have.

Thanks for coming tonight.

- This was great, thank you.

And we have several questions that have come in.

Ms. Gentler wants to know, can you tell when you're looking at this data, which organism might have recovered first from the mass extinction?

- You wanna take that?

- I think it can be tricky because it's hard sometimes for us to exactly constrain time at each of these different sites.

So, we're studying this mass extinction through time and through space, and figuring out exactly where we are in terms of how much time has transpired at each site can be really difficult.

We use the chemical signals, the shifts in the chemistry to figure out where we are in time, we use the fossils to figure out where we are in time.

So, if we can put that complex picture together, then yeah.

We would be able to say which animals were the first ones that appear in the rock record, but sometimes there are issues of preservation.

So, just because a fossil is the first thing to reappear doesn't mean that it's really the first thing to maybe evolve in the aftermath.

It may just be the first thing that actually got preserved in the aftermath.

So, you have to think that we're only able to look at hard-shelled critters, like clams and snails, but there could be all sorts of soft bodied animals like worms and other things that don't leave as good of a fossil record.

Think about jellyfish, anemones, that may have been around and we're not able to actually count them in our study.

So, there's a lot of complexity there.

Figuring out exactly where we are in time is difficult.

And even if we do, we're missing some data that's not preserved in the fossil record, we're really reliant on having hard-shelled animals left behind.

So, kind of yes, kind of no.

- In a simple way, what we're looking for, is like Carlie is saying, what are those first things that arrive, right?

Right after that extinction event.

You have the clay layer with the iridium, you have the tsunami layer of just a bunch of shells that have been broken up.

And then all of a sudden, you start depositing sediment again in a normal way, and you look at who's there.

You're not totally sure exactly when they evolved, but you can at least say, here's kind of the early things that we find.

And then we ask not just who's there, but also how many of them are there.

So, in sort of thinking about how recovery works, we don't just wanna know who's there, but we also wanna know how quickly they increase the number of individuals, increase their abundance through time, right?

- Thank you, that was great.

Jadah has a question.

When you are showing some of your examples and everything, there are some colors and textures.

So, how do scientists figure out what color and texture an organism was?

- That's hard.

Okay, so, most of the time we don't have any idea, which is actually why I absolutely love artistic reconstructions of fossil life, because a lot of it is in fact, artistic.

We don't actually have a record of color most often and especially things that are as old as the animals that we're talking about.

If you study things that are not quite as old, maybe things that have been dead for, I don't know, even maybe a million years or so, sometimes the chemical properties of the color in that animal can get preserved.

Not usually all of it, not like all of the chemical signal of the color blue, for example, but maybe just enough of the chunk of that, of that chemical record to say this was probably a blue color that is being preserved here.

And so, usually we can find that type of information not very often, you have to have really exceptional levels of preservation.

So, we call these Fossil-Lagerstätten, which in German means kind of like the motherload type of fossilization, where we're actually also preserving things like skin, stomach contents, sometimes even hair, right?

If you have that level of preservation, then sometimes you can also preserve these little bits of like the proteins that make different colors.

So, you have to be studying things that are not very old, and then you need to be studying things that are really well-preserved.

Mostly, we make it up.

(Nancy laughing) - It's good science.

I love that.

Dr. Pietsch, did you always know that you wanted to go into a science career?

- Yeah, I have always wanted to be a paleontologist since I was a little kid.

And I had some doubts along the way and thought about some other opportunities.

I also thought about fashion design, I also thought about being a vet, but I got to take geology classes and biology classes and start to actually work as a paleontologist, as a volunteer at a museum.

And that's what really sealed the deal for me when I was able to have that experience and go from there to go on and get degrees and be able to teach.

- Thank you, I'm gonna toss that same question to you, Dr. Myers.

- I had no idea what I wanted to be when I grew up.

I was the kid running around with chaos and bull in a China closet.

I was interested in everything.

And so, I actually was lucky enough to have a field studies class in high school that took me outside.

And at that point I said, I wanna do some kind of work that is outside.

And so, it sounded like geology would be the best thing that would give me the opportunity to work outdoors.

So, I started a geology degree, and then I waffled for another four years.

Maybe I'll do anthropology, maybe I'll do English.

Made it through my degree program thanks to some key people at the Paleontological Research Institution.

And then I decided I wanted to go study volcanoes.

And so, I did a Master's degree looking at the chemistry of volcanoes in the ocean.

And as I was doing that, I realized I wanted to study life again.

So, I switched gears and ended up going to school for a PhD in Paleontology.

So, my path was very windy, but I think what kind of kept me on the road was wanting to understand environments and how life lives in those environments.

So, when I finally found out that there was a thing called biogeography, which is how life lives in space, I was suddenly like, "That's what I wanna do."

I wanna be outside and study life.

- I think the takeaway is you have to try things to find out what you like.

You have to, you gotta experiment.

Yeah.

- I love that, and not to be afraid to take a crooked path to get there.

- It's never too late to sort of start a new thing and be successful at it.

- Dr. Pietsch, I know that you have to leave us soon.

So, I wanna ask you another question.

What is the coolest thing that you have found in the field?

- Oh man.

That's so hard.

I don't know.

Man, Cori, do you have, I don't have an answer.

What's the coolest thing?

- It is a really hard question.

Probably my favorite things are some of the, I mean, I love ammonites.

I imagine that came through pretty loud and clear.

Some of the really beautiful iridescent, kind of mother of pearl colored ammonites that you can get out of Cretaceous sediments in South Dakota.

And even in some places along the Gulf coastal plain, they just have incredible iridescence and they're beautiful.

That's probably my favorite.

- I thought of mine.

I found once a tiny coccolithophore, which is a piece of shell that plankton make, caught in between the layers of a snail shell when I was looking at it underneath the microscope.

So, it wasn't in the field, it was actually the lab, but that blew my mind and it was very exciting.

- That is super exciting.

Well, thank you Dr. Pietsch.

I know that you need to go, but Dr. Myers is gonna stay with us for a few more questions and we actually did have a question of somebody asking, why do you have such a love of ammonites?

- That's probably an even better question than what's my favorite fossil, right?

Because they're weird, is the short answer.

They're basically squids that lived in a shell, kind of like a modern nautilus, except their shells got really bizarre.

So, instead of just being a nice little coiled shell, they actually started uncoiling and they made all kinds of weird shapes.

There's ones that look like paperclips, there's ones that look like ice cream cones that are unraveling.

There's one called nipponites that I think looks like a pile of dog poop.

And you just wonder what the heck is going on.

How do you be an animal that is alive and eats, and very is sort of floats or swims around and have so many bizarre coils that you look like a pile of dog poop.

They're just weird.

And I love that.

And they're beautiful.

- Well, I love that you're bringing that into science.

So, it doesn't have to always be this super serious thing, it's that you can have some really funny and interesting things that either attract you in your field or that (indistinct) over.

We had a question from Jedo.

What did scientists think caused the Cretaceous mass extinction before the asteroid theory of 1980?

- I don't know.

Do you know?

- Yeah, I don't think I know either.

I'm gonna guess probably volcanoes because that's what killed everything else.

Or I guess they would've noticed climate change, but they wouldn't have known why, yeah.

- So, early on in the 1950s and '60s, the going rate on what caused extinctions was actually sea level change.

So, Norman Newell at the American Museum was kind of the first guy to say mass extinctions are important and we should be studying them, and actually counting how many things died instead of just making things up.

And so, his theory was that mass extinctions were caused by decreases in sea level.

And he's looking again at these shallow marine animals.

So, if you decrease sea level, you're gonna kill a bunch of things off.

And then there were a bunch of other weird theories that were being thrown around like large igneous provinces, big volcanoes, oceans that are anoxic in the bottom, but have oxygen on the top.

And then they overturned for some weird reason.

And all of a sudden you took all the oxygen out of the shallow water was one.

Some people thought that you would melt the methane that was frozen at the bottom of the ocean.

So, kind of like how methane is frozen in peat in the polar regions, you have ice basically made out of methane at the bottom of the ocean.

If you heat up the ocean, that'll melt, and then you have this "methane burp" where you're just throwing a bunch of methane which is toxic up into the shallow water and then also the land.

What were the other ones?

Those are kind of the big ones.

- Yeah, especially the sea level thing.

That was used to explain so many different things.

- And the asteroid impact hypothesis, I mean, that was a game changer, right?

I mean, people were kind of just sort of saying, should we care about these mass extinctions?

Maybe it's part of the record is sort of messing up our ability to see a mass extinction or not, you know?

And then when the Alvarez folks came out with this, it's actually an asteroid and then they found the crater, all of a sudden everything was caused by asteroids.

- Yeah, because we've got asteroidal fever where people are just looking for that evidence in rocks everywhere now, yeah.

- And then that has given way to volcano fever.

And now we think everything is caused by volcanoes except this one.

- And we actually have a question from Cindy, were there other meteorite impacts that caused some extinctions, but not as large as this one?

- That's so interesting too, 'cause there are impacts that are as big as this one or of a similar size that cause very little or no extinction also.

So, it really kind of depends on the rock that the asteroid hits.

So, this rock is vaporizing these sediments that are really carbon and sulfur rich, and that's changing the atmosphere and changing the oceans, but there's another really big impact crater called Manicouagan in Canada that hits granite.

And that doesn't really change the Earth's atmosphere as much 'cause it's mostly silica.

And so, that's not gonna interact with the oxygen and cause all of this atmospheric and climate devastation, I don't know, Cori, do you know of any other ones?

- Yeah, can I share my screen again real quick?

- Yeah, absolutely, sure.

- I have a graph that I can show you.

- Oh, cool.

- Tell me when you can see this.

- Yeah, we can see it.

- Go into present mode so we can see it a little bit larger.

- Okay.

- Present mode.

Okay, so, what you're looking at is time on the bottom.

So, 400 million years ago, and then zero on the right.

And then these peaks are extinction rates.

So, there's the end-Permian.

There's the end-Triassic, there's the end-Cretaceous.

This next one is volume of lava extruded by a large igneous province.

So, a big volcano.

And then on top of you're looking at crater diameter of different asteroids.

So, you can see that there are asteroids that have hit, the Manicouagan that Carlie was just talking about and a bunch of others, right?

But only in this one case does it seem like an asteroid impact actually triggered this mass extinction.

In this case, right?

We think it's this large igneous province, the Siberian Traps.

In the end-Triassic case, we think it's this Central Atlantic Magmatic Province or CAMP.

Same here, there's sort of a large igneous province, couple of them happening right at the end of the Devonian.

So, the end-Cretaceous really is actually a unique period where an asteroid seems to have caused a mass extinction.

But we also have extinctions where we have a lot of volcanism and we still don't have an extinction, right?

So, there's more to the story than sort of simply picking one or the other.

And that's what it's turning to.

- Dr. Pietsch, what do you find most rewarding about being a paleontologist?

- I have like two answers to that.

One is I really enjoy outreach to young kids who want to be paleontologist.

A lot of people find out that I'm paleontologist and they connect their children to me.

And it's actually really fun to like answer their questions.

And otherwise, I really love just a really complex, like interdisciplinary nature of paleontology, where you have to do the geology, you have to do the biology, you have to the chemistry, you have to understand a little bit of all of that and be able to work with other scientists to reconstruct this entire story.

It's really exciting in a field that is sort of always expanding to include other disciplines.

And I really love that about paleontology.

- And how about you, Dr. Myers?

- Like Pietsch you're thinking, right?

What do I love about paleontology?

For me, what gets me going is the questions.

I wanna know...

The big question is I wanna know how the environment impacts evolution.

How does changing environment cause speciation or contribute to speciation?

How does it contribute to extinction in contrast to the sort of biotic interactions, things like mutualism, symbiosis, competition, predation, that seemed to really impact populations, especially ones that we can observe today.

So, I'm really into some of these big questions.

How does evolution work?

How does it work at the level of species, and how is that different than how it works at the level of an individual organism or of a population of organisms.

And I wanna know that in the context of where they live and how does that environmental or biotic regime impact where they can live.

So, that biogeography component.

I also love teaching.

I'm a big fan of collaborative work and that includes students.

So, I love mentoring graduate students.

I love mentoring undergraduate students.

And to be honest, my biggest goal as an educator is to produce undergraduates who graduate college, who can be critical thinkers about science and who can be engaged citizen scientists, and view the world kind of through an evidence-based lens.

- And that's so important, that critical thinking.

I have one last question for you.

Either of you aware of an organism that has been accidentally claimed to be extinct, but wasn't?

- This happens all the time.

- Yeah.

- In modern biology, it happens all the time, right?

And we can all sort of think back to the ivory-billed woodpecker, and someone thought they saw one about 20 years ago.

Maybe they did, maybe they didn't.

But a lot of people were looking for it to try to see if that was real and whether they were really extinct or not.

Same thing with the thylacine, the marsupial wolf.

There was, "Oh, we thought we saw one."

So, maybe that wasn't quite extinct, but maybe it was.

In the fossil record, we call those guys Lazarus taxa, and their fossils that you'll see in one horizon of sediment.

And then they disappear for a while and then they come back, and we call them Lazarus taxa.

And they're a problem for us when we're trying to measure diversity, because clearly, they weren't extinct in that middle interval, we just didn't find them there.

- That is interesting 'cause where'd they go?

- Somewhere else.

- Well, like Carlie was saying, the preservation regime wasn't good for them.

Anybody that was there just got bashed to bits by waves or whatever.

- That's great, thank you.

Don Haas wanted to know if the snail, which I think was near the end of your presentation, was from "Doctor Who."

- It wasn't (laughing).

- So, what is next for you, Dr. Pietsch?

- Well, we're gonna continue to work on this project.

So, I showed you that room full of boxes of fossils, and we have lots of boxes to unpack and figure out the ecology and the size of all of the marine inverts that we collected in the field over the summer.

So, lots of work with myself and all of my students who are here trained and starting to excavate all that material.

- Well, that's really exciting.

That definitely will keep you busy, there was a lot there.

And how about you, Dr. Myers?

- Sort of similar.

So, Carlie's gonna send me some information about the species that she finds.

So, we're definitely kind of keeping each other up-to-date.

I'm also working with the geochemist on our team to provide her.

Her name is Dr. Sierra Petersen, at the University of Michigan.

We're providing her with samples of shell, of that carbonate shell, to try to look at stable isotopes of oxygen and carbon and get a sense for the temperature regime in our study sites.

And all of this information, what Carlie finds and also what Sierra finds, and then taking the sort of sedimentological information that we got from fieldwork, those go into my models.

And I have a graduate student, Yonei Noyaketite who is in charge of kind of putting all that information together as it comes in.

- That's great, thank you so much.

I really wanna thank you Dr. Corrine Myers and Dr. Carlie Pietsch and our friends over at the Paleontological Research Institution for connecting us.

This has been a great presentation.

So, thank you so much to both of you.

- Thank you.

- Thanks so much for organizing this, great.

- It's a pleasure.

- Don't love your jokes and your questions, thank you.

- To find more information about Dr. Pietsch and Myers' work, there are links that are in the chat.

You can follow those to find more about them.

Our next Science Pub is on Tuesday, December 14th, with Assistant Fire Chief, Rick Allen, on exploring the science behind fire and firefighting.

So, join us for "Sounding the Alarm: Milestones in Fire Science."

Rick will share why today's house fires are so dangerous.

They burn hotter and faster than they did decades ago and producing smoke that's highly toxic to firefighters, basically, because of all the stuff that we keep in our houses.

The link to RSVP is in the chat.

So, please sign up for that now so you don't forget to do that.

You can watch past Science Pubs through the WSKG app on demand on your smart device and on WSKG's website.

Be sure to like our Facebook page for future events and science updates, and those links are also going to pop into the chat.

I wanna thank Dr. Pietsch and Dr. Myers.

This was a fascinating talk and I really appreciated all of the great data slides and how you shared them in a way it was easy for all of us to understand.

I wanna thank WSKG team, Jackie Stapleton-Durham and Patrick Holmes, who were our chat moderators for tonight.

Andrew Pioch is our director and producer.

Julia Diana for live tweeting, and Kristine Keswer, also the co-founder of Science Pub.

I'm your host, Nancy Coddington.

Thank you for joining us.

(bright music)