ExtinctZoo - The Ice Age That Killed Over 80% Of All Life

Episode Date: May 3, 2025

We’ve all heard of the Dinosaurs extinction, and if you're a slight nerd like me, then maybe the Permian’s great dying too, however do you know about the first mass extinction, which was a super mega ice age on steroids? Didn’t think so!

No one goes to Hank's for his spreadsheets. They go for a darn good pizza. Lately, though, the shop's been quiet. So Hank decides to bring back the $1 slice. He asks Copilot in Microsoft Excel to look at his sales and costs to help him see if he can afford it. Co-pilot shows Hank where the money's going and which little extras make the dollar slice work.

Now, Hank has a line out the door. Hank makes the pizza. Co-Pilot handles the spreadsheets. Learn more at M365Copilot.com slash work. Scientists believe that extinction events occur roughly once every 30 million years or so. In like the life they eradicate, each one can take many shapes and forms, and widely vary in how much damage they cause. Sometimes life gets lucky, and carnage is restricted to a local area. While in other situations, everything ends up feeling some pain.

Thankfully, though, most extinctions, even global ones, aren't bad enough to have long-term dire effects, and nature usually recovers remarkably fast, sometimes within a few generations. However, this isn't always the case, and a certain percent of life has had the distinctest pleasure of living, or more likely dying, through what we call major extinctions, which simply put, are bad enough that they usually make the Earth look like a different planet, and formally are classified as calamities where 75% or more of all species die out. And in the last half-billion years, about five have been identified which matched this criteria. And this collective group has earned the nickname the Big Five.

Of the bunch, the deadliest to have taken place so far, was the Permian-Triassic extinction, which due to its severity has picked up popularity as of late. But the most infamous one is definitely still the KT extinction, which is when a giant asteroid smacked Earth and obliterated the non-avian dinosaurs. And thanks to its icon's status, many erroneously view it as the worst extinction ever. And yet it wasn't, nor was it even the second, as that title goes to a forgotten catastrophe that not only was way worse than the dinosaur-ending one, but is also, the only extinction to have given the great Permian die-off a run for its money, and in some

areas even has it beat. Not to mention that it also happens to be the first of the big five to have taken place. This was the late Ordovician mass extinction. To witness this event, you would have to go way back, like way, way, way back, before the dinosaurs, the Permian, or even the Carboniferous, to a time when even trees had yet to evolve, the Ordovician, a period which began some 486 million years ago. At the time, the earth was a true water world, with much of the land being marooned islands, while massive seas and oceans rose up higher than anything seen today. At certain times, possibly rising up to 2,000 feet or 600 meters higher compared to current levels, which have happened now

would create something like this. Even the land completely safe from flooding still got wet, as the climate was typically hot, humid and moist. And so with numerous tropical islands, plus humidity, you typically get a lot of life. But the lands of the Ordovician weren't actually that interesting, and the only thing you may have really seen were early plants that resembled liverworts or mosses, so not that cool. But if you ventured out into the waters, you'd soon realize that the story cannot be farther from how it was on land, as under the sea, life was absolutely thriving. And it was the kind of life that looked more like aliens than animals of today, with endless oddities being found here, which was largely thanks to something we still have, coral. These

invertebrates had already been alive for quite some time at this point, but it was in the Ordovician that they started to reef build, leading to expansive reefs across the world, which helped support the likes of animals not seen before, including the endocerids, a group of extinct cephalopods who were very diverse, and in some cases, giant, with the biggest, Cameroceras and Endoceras, possibly growing to 9.14 meters or 30 feet long, and that was just their shells, so in reality, they were possibly 10% longer. And some reckon that the biggest specimens might have cracked one ton, which, if true, would make them the first known animals to do so. and equipped with powerful tentacles, in a mean old sharp beak that could tear and crush through most animals,

they were probably the dominant apex predators, likely sticking to the sea floor where they could scour the bottom for any unfortunate victim, including one that was a very common face at the time, trilobites. You might not know these guys, but you should, because while not terrifying, they were extremely successful, being in fact one of the most accomplished animals of all time. And though they lived hundreds and millions of years ago, they are still known by over 22,000 species. so you can bet that they came in endless shapes and sizes and filled many niches, with some even learning to venture onto land from time to time. They were also found globally and virtually in every environment, which sadly also meant that a lot of predators, besides several pods ate them, including the brand-new Euripterids, more commonly known as Sea Scorpions.

These guys generally had body plans that made their lethality evident, but overall they were still diverse and differed quite a bit. Some had appendages to scoop, others to grab, or in certain cases, rip things apart. And their tails could differ too, as a few opted for more paddle-like tails aiding in locomotion, while a handful developed non-venomous stingers that could shank prey repeatedly. Now, back then, while they were successful, they hadn't quite yet reached their peak, as that would come later on during the Silurian, and this translated into many actually being rather small. Although, like usual, there are always exceptions, and large human-sized eryptorids weren't unheard of, and were probably apex predators as well, evidenced by copy. operolites, or fossilized herds, which showed the presence of jawless fish, trilobites, and even

other sea scorpions in their diet, and thus making them among the first-known cannibals. Talk about being a trendsetter. And if this wasn't freaky enough, you also had the enigmatic conodonts, who frankly can only be described as eel-like creatures that had big bug eyes and the freakiest mouths imaginable, filled with what scientists have concluded are the sharpest teeth of any animal ever, being just one-twentieth the width of a human hair. It might have been used like how modern hagfish and lampreys used their teeth. So the stuff of nightmares, to say the least. Plus, it didn't help that they were essentially found in every level of the oceans and seas, not just the bottom. So avoidance

was off the table. And to finish this bizarre world off, you also had the Radio Dantes, who straight-uped looked like something out of a sci-fi movie, and were exceptionally diverse, to the point where if you can think of a way to kill something, chances are one of them did it. And across the In the board, species were known to be raptorial predators, sediment sifters, suspension feeders, and filter feeders. Perhaps the most exceptional Ordovician genus was the Agirocassus, a giant radiodont that outsized most humans and lived off the coast of what is today Morocco. So evidently, this truly was an alien earth, and the weirdness did not stop at life, because

on land, during the night, or perhaps even during the day as well, if you glanced up, you might have seen rings, yes rings, like those of Saturn. Back in the day, researchers noticed that Ordovician formations had an abundance of el-condrite meteorites stuck in them, enough to assume that a massive celestial body had been torn apart by Earth's gravity half a billion years ago, and thus leading to the formation of a ring around Earth and spawning the late Ordovician meteor event, a period of 40 million years where meteors rained down a hundred times more often than presently, creating some really metal sights, with countless shooting stars and rings hovering above you while expansive oceans were laid out all around. But sadly, these sites would not remain, as approximately 445 million years ago, Earth encountered the first of the Big Five, the late Ordovician mass extinction, or loam, for short. This doomsday, even for mass extinction, is highly debated, and no one can really agree on what caused it. However, the mainstream hypothesis is that things essentially got really, really cold, with a massive

ice age having plunged Earth into total darkness. It's formally referred to as the Hernatian Glaciation, and was characterized by the Harnatian by ice caps forming across much of the world, with sites from most of Africa, South America, and parts of North America, all showing signs of extensive glaciation, which at its peak could have held 250 million cubic kilometers of ice, 10 times greater than the volume seen in the current Antarctic ice sheet, which, by the way, holds about 61% of Earth's total freshwater. And scientists reckon that this prehistoric ice age was unlike anything seen during the one humans and woolly mammoths lived through, and temperatures could have dropped by over

8 degrees Celsius or 14.4 degrees Fahrenheit. In other words, if you live in New York, it would suddenly be like living in Iceland, but worse. And this rapid cooling froze a lot of animals, you could say, and caused massive fluctuations in the climate, wreaking havoc in every environment. And nature was especially cooked, no pun intended, given their aquatic preferences, because as the ice sheets expanded, the sea levels retracted, resulting in huge habitat losses, including the destruction of the majority of coral reefs and their inhabitants. And at its worse, waters may have fallen by over 125 meters or 410 feet, which if happened now would result in something like this.

And to add insult to injury, the retreating waters exposed large amounts of seafloor, which contained rocks and minerals that drew in carbon dioxide as they weathered, leading to yet colder temperatures and more extinctions. And all this pain and suffering would not have been like gripping off a band-aid, but rather slowly pulling it, reapplying it, and then pulling it again, because this ice age potentially lasted for 35 million years, longer than the complete entirety of certain periods. And it was around this point that the late Ordovician mass extinction saw its first wave, or pulse, of major die-offs.

Animals extremely impacted by this first stage included the brachio-pods, echinoderms, trilobites, and bryozoans. And strangely, while many shallow waters were basically turned into land, it was actually deep sea species that seemed to be especially heavily impacted by this pulse, with some paleontologists explaining this through a global anoxic event, wherein the amount of oxygen in the water lower to toxic levels, and thus killing many animals as cells cannot function without adequate amounts. Furthermore, some hypothesized that counterintuitively, warming periods sprinkled in before and during the actual ice age, may have played a hand too. Now, while it was mainly the smaller animals

who were bomb blasted by the destruction, larger ones did not remain unscathed, as multiple species of euryptorids and cephalopods disappeared, while radiodons took a hammering too. But as Ian Malcolm so eloquently put it, life finds a way, because animals didn't just survive, but rather expanded into whole new groups, who were better adapted for a cold water world, and are collectively referred to as the Hernantian fauna. Despite this small win, we still ultimately struggled in these bitter times, and things might have been even worse than simple bad weather. As a few studies have stated that as the oxygen was depleted, toxic metals started to seep into the sea floors, namely high concentrations

of mercury, which decimated lower trophic levels in the food chain, eventually causing or aiding in its entire collapse. For any animal, the end of this nightmare could not have come quicker. And yet ironically, when the Ice Age finally did give in, it somehow led to a whole second round of hurt, distinct from the first one, and has been categorized as a second pulse. Because Because as it turns out, if you get used to something, even something bad, it can still be hard when it leaves. And like the first wave of death, a lot of mystery surrounds this, too. However, the general idea is that around 420 million years ago, the cold times abruptly

stopped, leading to a collapse of the Ice Age, possibly spurred on by its own success. Because as mentioned, the extent of the ice was almost incomprehensible and much greater than anything since the Mesozoic. And because the sheer size of it was so expansive and heavy, almost like a giant, tests of cards, it eventually came crashing down under its own weight, and then spilling into the sea, leading to a rapid increase in sea levels, and then promoting global warming, leading to a rather rude wake-up call for all those who had grown accustomed to the cold and shallower waters.

What's more is that as the sheets vanished, they possibly released large amounts of nutrients back in a circulation, while simultaneously increasing the amount of sunlight, resulting in massive algal blooms, which covered huge chunks of the oceans and seas, that tragically killed many of the few animals left standing. In between the rise and collapse of the Hernantian glaciation, Earth had taken quite a beating, and when the dust finally settled, very little of what was remained. In the end, between 49 and 60% of all Marine genera was eradicated. In seeing that most life was aquatic, this basically meant that half of all life was gone.

And included among the fallen was one-third of all brachio-pod and brazoan families, and many groups of conodonts, corals, and trilobites, the latter of which, lost 50% of all their families, and despite their tremendous resilience, would never recover. The endocerids, who have been the rulers of Earth, also did not come out on the other side in one piece, with this event having been their curtain call and marked the last time the world ever saw cephalopod as the top dog. However, as a whole, they still remained strong all things considered. A group that managed to do even better than them were the sea scorpions, retaining most of their biodiversity and very quickly expanding into this empty world,

becoming one of the most dominant animals during the Silurian. And another comeback story was seen in theankanoderms. Unlike the sea scorpions, they had actually been almost wiped out by the last Ordovician mass extinction, losing about 70% of all the genera. And yet, against the odds, they bounced back very quickly, finding success in the new tropical shallows that formed during the early Silurian. And within a not-so-long time, they were back to normal. Unfortunately, though, not everyone could brag about such a miraculous comeback.

I mean, just asked the brachio pods. To say this group got swindled by the extinction would be an understatement. Beforehand, their level of diversity and abundance was off the charts. And then afterwards, well, very much on the charts, with the vast majority having perished while the survivors who were left were far and few in between. And of those that did survive, many displayed the Liliput effect, which is when an animal becomes smaller after mass extinction. And as a testament to the hardship they faced, it turns out that many groups of brachio pods

that are still alive have not yet recovered, even nearly half a billion years later. Talk about bad luck. Others, like the conodonts, found themselves a bit in the middle in that they eventually recovered, but it took a substantial amount of time, in their case an entire geological period, not peaking in diversity again until the Devonian. In a similar case was also seen in Fish, who, while not super dominant nor diverse, still took a hit, and would also not really pop off again until the Devonian, which coincidentally is nicknamed to the Age of Fish. So clearly, this mass extinction left the earth in a rather poor state, and is the only one of the Big Five who has the Permian extinction beat in an important area. With that being, the number

of marine families lost, as up to 87% were erased, while during the Great Dying, this number was only around 81%. Additionally, studies have found that it might have felt worse too, in that during its peak lethalness, animals were dropping like flies faster than what was seen in the Great Dying, and ultimately it would take at least 5 million years later for nature to recover from this night Maybe 20, meaning that entire species, genera, and families born and died in a post-apocalyptic world. Which thus leads us to our final question. Where did this massive ice age even come from?

Well, no one can be sure, but multiple ideas have been put forth, the most straightforward of which is that Earth had set up its own failure through geography. You see, during the Ordovician much of the world's land was further south than today, and the tectonic plates kept pushing it all, especially Gondwana, closer and closer to the South Pole. eventually resulting in a freezeover and therefore the ice age. However, given how quick the ice age sprung up and how slow titanic plates move, it's now thought that geography alone can't explain what happened, leading to other potential factors,

the scariest of which is also the most colorful, the collapse of a star. In other words, a hypernova, and more specific to Earth, a gamma ray burst. In the early 2000s, it was proposed that a gamma ray originating from 6,000 light years away have been the true culprit behind Earth's first mass extinction. It smacked the planet in a 10-second burst, causing rapid glaciation, as disassociated oxygen from the ozone might have reacted with nitrogen. Not to mention that a 10-second gamma burst alone would do serious damage, stripping away half of the ozone and exposing organisms to extreme levels of UV radiation, only exacerbated

by the unusual clarity of Ordovician waters. Now, I will say this is not a heavily supported idea, and in recent years, equally interesting ones have risen to replace it, including an asteroid impact like the one that took out the dinosaurs. Only this proposed one makes the Dinoender look like a pebble. In 2023, researchers located a buried structure in Australia that resembled something an asteroid would make. However, because it's buried so deep, it's hard to tell what it exactly is. For now, though, it's been dubbed the Denoquin Multiple Ring feature.

And if it was truly asteroid made, then its measurements indicate a crater greater than anything else known on Earth. having a diameter of 520 kilometers or 320 miles. So, uh, nearly three times larger than the KT asteroid. Rendering it big enough to not only decimate to life upon impact, but also to easily usher in a full ice age as well. However, the founders of this site have clearly stated that more studies are needed to verify their findings.

So for now, it's just another daunting possibility to add to the list. And while all these ideas are no doubt captivating and terrifying, the one that has gained the most steam is something extinct activists are all too familiar with. Volcanism. Volcanoes have a tendency to cause problems when they blow, and according to some, this is exactly what happened back then. Typically, we think of volcanic eruptions causing extinction through global warming. I'm looking at you, great dying. But this time around, it seems that volcanic activity, possibly stemming from present-day Iran, may have caused a cold spell by emitting massive amounts of sulfur. Although, a subset of the subset,

who support volcanic eruption, I actually think that a quick heat burst is what actually did the heavy killing. But who knows? And somehow even this doesn't exhaust the list of possibilities. As the rings that circled Earth, two have gotten blame via their giant shadows, while even life has experienced finger pointing, as some suggest that plants colonizing the land cause a sharp drop in carbon dioxide and thus leading to an ice age. Regardless, though, while the debate will likely continue to rage for years to come, one thing is certain. You did not want to be an animal, or really anything, during it.