In short
A journey to the Cairo, New York quarry “ghost forest” showing tree root impressions from 385 million years ago, explaining the Devonian “plant explosion,” the rise of early forests and land vertebrates, and how that same expansion may have triggered the late Devonian mass extinction in the oceans.
Guest backgrounds
Lisa Amati, New York State Museum state paleontologist who curates hundreds of thousands of fossils; Chuck Verstratton and Meredith Hottonott (host/reporter) discuss the site; Thomas Algeo, geologist who studies mass extinction events.
Key claims
Rooted forests transformed Earth’s atmosphere (CO2 down ~90%, O2 up), helped drive climate cooling/ice age, and via nutrient runoff fueled algal blooms that depleted ocean oxygen, causing widespread marine die-offs.
Notable examples
Devonian “fungzilla” (a fungus-like early land organism), Cairo Quarry tree types (broccoli-headed palm-like trees, club moss gone giant), and the “Age of Fishes” ending with oxygen-starved dead zones.
Written by AI. May contain mistakes. Listen to the episode to check what was said.
Chapters
Tap a time to open that second in VOEntering the Quarry
0:33 to 1:50
The hosts describe the journey into an old quarry and the discoveries within.
“But switching to GEICO saved me hundreds, so my bank account is safe.”
Ancient Tree Discoveries
1:50 to 4:42
Discussion about ancient tree roots and the significance of fossilized impressions.
“It's definitely nothing living inside that area.”
Paleontology and Fossils
4:42 to 6:34
Introduction to the paleontology collection and the work of professionals preserving fossils.
“It's like, yeah, it feels hard to wrap your head around, especially when it's, I don't know, when you're looking at what it is now.”
The Devonian Period
6:34 to 11:28
Exploring the evolution of life and the significance of the Devonian period in Earth's history.
“We are walking through a room that looks kind of like the warehouse at the end of Raiders of the Lost Ark.”
The Devonian Plant Explosion
11:28 to 14:03
Discussion on the transformation of Earth by early plants and their impact on biodiversity.
“What do you think is so, I don't want to say the word enchanting, I'm not sure if that's right, but just like enthralling about the Cairo site?”
Car Insurance and Geico Savings
14:03 to 14:33
A humorous take on car insurance experiences and savings with Geico.
“I've invested most of my winnings in chicken tenders, because they're bomb.”
Car Insurance and Geico Savings
14:36 to 15:08
A humorous take on car insurance experiences and savings with Geico.
“It's the only business software you'll ever need.”
Mass Extinction and Ocean Life
15:49 to 16:36
Exploring the impact of mass extinction events on ocean life during the Devonian.
“By the end of the Devonian, once teeming seas were now a graveyard.”
Triggers of Mass Extinction Events
16:42 to 17:33
Discussing the environmental changes leading to mass extinctions triggered by trees.
“Geologist Thomas Algeo studies ancient apocalypses.”
The Role of Trees in Ecosystem Change
17:44 to 19:47
Describing how the Devonian plant explosion altered ecosystems and contributed to extinction.
“But it also changed how the planet worked, how the air, the soil, and the water all interacted.”
Show all 14 chapters
Algal Blooms and Marine Dead Zones
19:51 to 20:41
How tree flourishing led to nutrient runoff and devastating algal blooms in oceans.
“Soils don't just help plants grow on land.”
Investigating Devonian Extinction Evidence
20:53 to 21:42
The challenges in determining the cause of the Devonian extinction compared to others.
“For the asteroid that killed the dinosaurs, there is clear, direct evidence.”
Fossil Records and Global Patterns
21:45 to 22:42
The need for comprehensive fossil records to understand past mass extinctions.
“Well, what's really needed is a better record of the evolution of land plants themselves.”
Reflections on Past and Present
22:47 to 24:29
Connecting past mass extinctions to current climate challenges and human impact.
“As I walk across the quarry floor, the distance to the past seems permeable.”
Transcript
Automatic transcript. May contain errors.0:00Lisa Amati:Support for this show comes from Fetch Pet Insurance. Do you have a pet? Every six seconds, a pet owner in the U.S. gets hit with a vet bill of over$1 ,000. And it's almost always an unwelcome surprise. That's where Fetch Pet Insurance comes in. Fetch is the most complete pet insurance. Get paid back up to 90 % of vet bills. You can use any vet in the U.S. and Canada. All vets are in network. Go to FetchPet.com slash save right now for your free quote. That's FetchPet.com slash save.
0:58Charles Ver Straeten:But switching to GEICO saved me hundreds, so my bank account is safe. It feels good to save some hard-earned cash. It feels good to GEICO.
1:09Lisa Amati:At the far end of town, where the back roads wind past the little diners and campgrounds closed for the season. Into the woods we go. I feel like it's just starting to be spring. I can feel it.
1:25Charles Ver Straeten:Thank God.
1:26Lisa Amati:Just when you think you've missed it, turn left into an unmarked driveway. Past the fences and the no trespassing signs. Alright, ah, another chain link fence. And a much more secure padlock. Oh my gosh. And you'll finally arrive. At a huge, empty gravel lot. It's definitely nothing living inside that area. An old quarry long out of use. A lot of gravel.
2:08Lisa Amati:Some birds, too. But look carefully at the dusty ground. You might just see the rocks that transported Chuck into the past.
2:19Thomas Algeo:Just thinking about time, like geologists think about time in millions of years, hundreds of millions of years, by looking in the sedimentary rocks. All this stuff is big scale. It's, you know, only astronomers think in a much bigger scale. I love this. They're not the oldest rocks in the world at all, but they are mighty old. Mighty old. Yeah.
2:49Thomas Algeo:And we're walking across this quarry floor, and my eye just unconsciously picked up on an odd pattern in the quarry floor. It looked like a shallow little gutter that kind of meandered back and forth a little bit while it went out, mostly in one direction. And it's like, what is that? And we started looking around and followed them, and three of these all met at one place, along with eight more of these gutter things that had gotten wider as we walked towards where they met. And it didn't take too long before we realized, all of us individually realized, wow. Wow. That is where a tree stood 385 million years ago.
3:45Lisa Amati:Holy shit. Unbelievable. So this was one tree.
3:54Charles Ver Straeten:Are we saying that this is literally two trees, like the star formations are like the basis of these two trees? Yeah.
4:04Thomas Algeo:The impressions of the roots. Well preserved.
4:08Lisa Amati:Like the footprints, almost.
4:10Thomas Algeo:Yeah, it would be like footprints, but the impressions of the roots, where they were in the ground.
4:16Lisa Amati:You know how big that tree was? Do you know what I mean? Yeah, no, I mean, literally, I think it looks like the trees that we can see on the other side of the fence. Tree-sized. Tree-sized.
4:26Thomas Algeo:We could stand where a tree stood 385 million years ago and see by the impressions of the roots where all the other trees in this forest stood.
4:41Charles Ver Straeten:It looks so magical.
4:45Lisa Amati:It's like, yeah, it feels hard to wrap your head around, especially when it's, I don't know, when you're looking at what it is now.
4:52Thomas Algeo:I mean, so many individual lives have lived on this planet. Everything died, left behind something, but most of everything decays, is broken down, dissolved. It's all about Earth, life, and a lot of time. such an awesome, awesome, awesome thing to imagine a forest from that long ago.
5:50Lisa Amati:Way back, way, way back, when these trees stood tall, Forests like this one exploded across the planet, radically transforming the earth beneath their roots, the air rippling through their leaves. You can see the aftermath of this explosion in the world all around us, but nowhere more clearly than these ghostly footprints etched into the dusty ground. I'm Meredith Hothnot, and this is Unexplainable.
6:33Lisa Amati:So this is the paleontology collection at the New York State Museum. All right.
6:40Charles Ver Straeten:We are walking through a room that looks kind of like the warehouse at the end of Raiders of the Lost Ark. The fossil collection has lots of stuff sitting in the aisles and on tables.
6:53Lisa Amati:Carts are full. Lisa Amati cares for hundreds of thousands of fossils here in her job as the state paleontologist. Lisa and geologists like Chuck Verstratton piece together fragments of an ancient past that they can't ever study directly.
7:12Charles Ver Straeten:Whenever I'm working with the fossils, I'm picturing where they lived. I'm picturing how they lived.
7:17Thomas Algeo:And it's like not just thinking about the rock and its character, not just thinking about the fossils and what they tell me.
7:26Charles Ver Straeten:It's a mystery novel. It's an adventure novel. It's a puzzle. It's everything all in one. We don't have the answers, which is what makes it fun.
7:37Lisa Amati:Our story starts in a time before trees, about 420 million years ago, at the beginning of the Devonian period. Earth's continents were bunched up in the southern hemisphere, and the land they carried would have been unrecognizable.
7:56Thomas Algeo:There really wasn't much of anything on land at all.
8:01Lisa Amati:In fact, nothing lived on land except for some tiny plants and the ancestors of things like insects. There were very few signs of life, all of them weird. This thing's 12 feet tall. So what could it possibly be? It can't be a plant. It can't be an animal. Turns out it's a fungus. Whoa, this is a fungus. Oh, and we call it fungzilla. This was a landscape of barren rock and gravel, buffeted by winds and rains. The loneliest alien planet. But underwater was a different world.
8:43Thomas Algeo:It was so much life in the oceans.
8:47Lisa Amati:The Devonian is known as the Age of Fishes because there were so many kinds of fish. All of the major groups of fish were alive during the Devonian period. There were jawless fish that looked like dune worms crossed with horseshoe crabs. There were placoderms, these fish plated in armor with huge Siberian tiger fangs. Sharks spread through the oceans at this time, as well as lobed finned fishes with bony little limbs. And the abundance of life in the ocean was just beginning to make its way onto the land.
9:29Charles Ver Straeten:Plants started to evolve from algae to be able to survive in a wet environment, but out of the water.
9:35Thomas Algeo:At the beginning of the Devonian, your tallest plants were only about the reach between your thumb, the end of your thumb and the end of your index finger, you know, four, five, maybe six inches.
9:47Lisa Amati:And once plants on land got a foothold, they started evolving faster and faster.
9:53Thomas Algeo:By 35 million years later, if we're talking about the Cairo Quarry, everything had evolved through stages of those simple little plants to things that began to become more complex, began to grow into shrubbery-sized plants, and then by the middle of the Devonian, you had trees. You had trees.
10:19Charles Ver Straeten:Big portions of New York were underwater, and the Appalachian Mountains were just forming and they were huge, really tall mountains.
10:28Thomas Algeo:Andes scale mountains perhaps out there in New England.
10:32Lisa Amati:And in the tropical floodplains between the mountains and the sea, the Cairo Quarry Forest flourished with the strangest trees. Broccoli-headed palm-like trees, draping evergreen ancestors, club moss gone giant.
10:48Charles Ver Straeten:It's like a furry telephone pole.
10:51Lisa Amati:And also smaller plants.
10:53Thomas Algeo:Little things like liverworts.
Read the full transcript
10:55Charles Ver Straeten:Liverworts are just cool. If you don't know what one is, you should look one up.
10:59Thomas Algeo:Teensy little leaflet-like things.
11:01Lisa Amati:The land now had these rich habitats, full of resources and shelter. Like an empty house, ready to be a home. And so the first lobe-finned fishes evolved little finny legs and crawled up from the water into the forests. These were our ancestors The first vertebrates on land The beginning of all the amphibians, all the birds, the dinosaurs, and us
11:37Charles Ver Straeten:And that's about where we are here in New York We had everything, vertebrates, invertebrates, and plants on land at this time
11:55Lisa Amati:So this is one of the first full forests on the planet Earth.
12:02Charles Ver Straeten:Unbelievable.
12:04Lisa Amati:Totally.
12:05Charles Ver Straeten:Crazy.
12:09Lisa Amati:What do you think is so, I don't want to say the word enchanting, I'm not sure if that's right, but just like enthralling about the Cairo site? Why do you think it, like, sparks so many people's imaginations?
12:26Thomas Algeo:It's the oldest perspective. It's the oldest sense we have of first forests, where you can actually look out across the forest floor and see where all these trees stood. But this is a big perspective. It's really the Devonian period. when life first really colonized the land to a large scale. It was that Devonian period. Yeah.
13:01Lisa Amati:The tropical floodplains of upstate New York were a perfect place for these forests to take root. Monsoons rolled off the towering Appalachian Mountains, drowning the marshes and swamplands under epic floods. It was wet, but also it was warm. Ideal for plants starting to figure out how to live on land. And then, explosion. And it's actually literally called the Devonian plant explosion. Life had found a new home on the land, and there was no stopping it. Plants raced across this barren, rocky world, an explosion of biodiversity, transforming the world from gray and blue to green and blue. into a planet we'd more or less recognize today.
13:53Lisa Amati:And in doing so, they might have caused one of the biggest mass extinctions in the history of the world.
14:02Charles Ver Straeten:When I got a new car, I thought my insurance premium would increase and empty my bank account. Like if Fatween won the lottery. I've invested most of my winnings in chicken tenders, because they're bomb. But bro, I bought a house, and it's sick, bro. I'm thinking the floor is going to be all trampoline, bro, with the helipad on the roof. The contractor said it's structurally unsound. They're just being babies. But switching to Geico saved me hundreds, so my bank account is safe. It feels good to save some hard-earned cash. It feels good to Geico. Support for this show comes from Odoo. Running a business is hard enough, so why make it harder with a dozen different apps that don't talk to each other?
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15:48Lisa Amati:The story of life exploding on the land is also the story of life dying in the oceans. By the end of the Devonian, once teeming seas were now a graveyard. The carnage of one of the biggest mass extinctions in the history of the planet. an extinction as violent as the one that killed the dinosaurs. Nearly three-quarters of the species on Earth died in this slowly unfolding catastrophe. And the oceans suffered worst of all. Corpses littered the seafloor. The age of fishes was over.
16:35Charles Ver Straeten:It takes a certain degree of imagination to see that things were different in the past. And the deeper back you go into Earth history, the more bizarre they are and the more foreign they are to what we're familiar with.
16:51Lisa Amati:Geologist Thomas Algeo studies ancient apocalypses.
16:55Charles Ver Straeten:I've effectively delved into all of the mass extinction events in Earth history.
17:01Lisa Amati:Our planet has nurtured life for billions of years. It's been a remarkably stable place to live and thrive. And in that long history, there have only been five times when the world was flung into such chaos that a majority of the species on Earth were wiped out before they had a chance to adapt.
17:24Charles Ver Straeten:And for that to happen, there has to be some kind of trigger, some kind of external trigger that upsets the system.
17:33Lisa Amati:And Thomas thinks that this mass extinction in the oceans was triggered by the trees.
17:43Lisa Amati:The Devonian plant explosion changed the face of our planet. But it also changed how the planet worked, how the air, the soil, and the water all interacted. These first forests did what forests still do today. They pulled carbon dioxide from the atmosphere and released oxygen. But this scale of photosynthesis was something totally new. Trees basically remade the atmosphere. dropping carbon dioxide levels by maybe as much as 90 % and doubling the oxygen.
18:21Charles Ver Straeten:And that is a big increase. That brings us up close to modern oxygen levels.
18:28Lisa Amati:This giant swing is one of just a few times living beings have disrupted the atmosphere so dramatically. These first forests upended the climate and plunged the Earth into an ice age that enveloped the world for tens of millions of years. But an ice age alone doesn't necessarily lead to mass extinction. There was a second punch coming for the age of fishes, a wave of death spreading out from the land. The roots of these first forests dug deep into the earth, breaking up rock and releasing minerals. The trees then died, decomposed, and formed new layers of carbon-rich soil. As the forests grew, so did the soil, which made it easier for younger plants to take root and help those forests grow, which then led to even more soil.
19:35Charles Ver Straeten:And there's a positive feedback there. But eventually, the nutrients are going to leak out into the groundwater system. They'll get flushed out of the soil, into the groundwater. The groundwater runs into a local river basin somewhere. The river carries the nutrients down to the ocean.
19:56Lisa Amati:Soils don't just help plants grow on land. They also help plants grow in the water. And so as these trees flourished, they helped fertilize huge blooms of algae, with devastating consequences for the seas.
20:13Charles Ver Straeten:As those massive algal blooms died and decayed, it robbed the waters of dissolved oxygen.
20:21Lisa Amati:Without dissolved oxygen in the water, marine life couldn't breathe. Huge dead zones spread across the world's oceans, enveloping vibrant coral reef communities in a vacuous cloud of death. Suffocating the age of fishes.
20:41Charles Ver Straeten:And that's effectively what I think happened during the late Devonian.
20:53Lisa Amati:For the asteroid that killed the dinosaurs, there is clear, direct evidence. A giant impact crater in the Gulf of Mexico and a layer of extraterrestrial dust flung across the globe.
21:07Charles Ver Straeten:It's very testable. But the Devonian planets are different because you're looking, the evidence is indirect. You see big changes in climate and environmental conditions, but you can't simply say those are due to the influence of land plants. They could be due to other triggers.
21:27Lisa Amati:So did trees pull the trigger on this mass extinction? Or did they set the world up? Did they put it in front of the gun and set the stage for some other trigger, like a volcanic eruption? Thomas is determined to find out.
21:45Charles Ver Straeten:Well, what's really needed is a better record of the evolution of land plants themselves. But if you find a fossil in one place, it doesn't necessarily tell you anything about what's going on in another place. So for some kind of global pattern, you literally have to go out and analyze the changes in dozens or maybe hundreds of different locations in order to be confident you're looking at a global signal.
22:10Lisa Amati:There are countless fossil forests around the world, like the one here in Cairo, that could shed more light on the Devonian plant explosion. But they're buried under earth and rock, still waiting to be discovered.
22:41Lisa Amati:So there was a time before forests, and then the world was never the same again. It's an insane story.
22:56Lisa Amati:As I walk across the quarry floor, the distance to the past seems permeable. Unbelievable. I can retrace the steps of my amphibian ancestors, imagine them scampering from tree to tree. This forest was their first home on land, the beginning of life as we know it, the reason I'm even here, millions of years later. In that light, the carved lines of ancient roots seem like etchings in a stone shrine, a monument commemorating these trees, these heroes that filled this fresh spring air I'm breathing with oxygen.
23:41Lisa Amati:There's also a darkness here around the edges. A somber memorial to a mass extinction that killed the majority of life on Earth. A tombstone to the Age of Fishes, marking a violent revolution that overturned the planet. Wow. Such a double-edged sword. Yeah, to think about, like, life finding new homes to be as explosive, as violent as an asteroid.
24:14Charles Ver Straeten:Yeah, yeah, absolutely. Wow.
24:18Lisa Amati:But the past feels closest when I think about the present. We are now the life transforming Earth's climate and ecosystems. We're releasing carbon into the air that these first trees and their descendants buried in the ground so long ago. We are on the brink of the sixth mass extinction in the history of the planet. Maybe the second one ever caused by living beings. And I can't help but wonder, how will we be remembered?
25:05Lisa Amati:Alright, it's hard to leave. This is such a magical place. Absolutely.
25:30Lisa Amati:This episode was reported, produced, and scored by me, Meredith Hottonott. It was edited by Jorge Just with help from Brian Resnick. Christian Ayala did the mix, and we collaborated together on the sound design. Melissa Hirsch checked the facts. Mandy Nguyen is lost in a good way. Bird Pinkerton is on the hunt. And Noam Hassenfeld got stuck in a black hole. Or maybe he was there all along. Special thanks to Bill Stein, Chris Berry, Lucas Pollock, Sarita Morris, and the town of Cairo. And a huge thank you to Brill Barajas for making this adventure so magical. And also, thank you, Milo Chestnut, for sharing your wonder and curiosity.
26:22Lisa Amati:I love you guys. I couldn't have made this story without you. You can also support us and all of Vox's journalism by joining our membership program. You can go to vox.com slash members to sign up. And if you do, you'll be helping make this place run. You also get unlimited access to all the phenomenal reporting on vox.com. You'll get exclusive newsletters and you'll get all of our podcasts ad free. Unexplainable is a part of the Vox Media Podcast Network. We will see you next week.
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From the publisher
Way back when forests first evolved on Earth... they might have triggered one of the biggest mass extinctions in the history of the planet. (Originally aired in 2024)
Guests: Charles Ver Straeten, curator of sedimentary rocks at the New York State Museum; Lisa Amati, curator of invertebrate paleontology at the New York State Museum; Thomas Algeo, professor of geochemistry at the University of Cincinnati
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