When it comes to preserving fossils,  we know that the ideal way to keep them safe is to cover them with  new sediment really, really gently.

Like packing up your glassware when you move. You want to be careful and put down lots of cushiony layers to keep everything protected.

And you know what that doesn’t  make me think of? Volcanoes. But, it turns out, in the right circumstances, volcanic activity can actually be the key  to preserving some incredible fossils.

So here are a few times a cataclysmic volcanoes managed to preserve picture-perfect fossils. [♪ INTRO] We’ll start off at one of the most  incredible fossil sites in North America, the Ashfall Fossil Beds in Nebraska. The site is about 12 million years old,  and excavations here have uncovered hundreds of fossil skeletons  of rhinos, camels, tortoises, and other animals, all preserved in  a massive deposit of volcanic ash. And funny enough, that volcanic ash  wasn’t even from anywhere in Nebraska.

It came from a volcanic eruption 1,600  kilometers away in what’s now Idaho. It’s called the Bruneau-Jarbidge eruption  center, and it’s part of the same volcanic system as the supervolcano  that’s underneath Yellowstone today. When this volcano erupted  around 12 million years ago, it spewed out a ton of ash that was  then blown all across the continent.

All the way to a thriving  waterhole full of animals just minding their own business, until  that ash began to fall from the sky. The ash was falling, Ashfall Fossil beds, eh? Anyway, this ash didn’t just bury the animals.

The ash is what killed them. See, volcanic ash isn’t like a little snow flurry. The particles are fine enough  that animals can easily end up breathing the ash into their lungs,  and that’s about as bad as it sounds.

Many of the fossilized bones have  these kinda frothy-looking growths that are associated with respiratory  issues, so these fossils show us that the animals died as a consequence  of breathing in all this toxic gunk. But we can even tell what order the animals  died in, just by looking at the layers. The lower down they are in the  ash layers, the earlier they died.

Small animals like birds and  turtles are buried deepest, meaning they died first, as ash continued to fall. Then we start finding medium-sized animals  like the ancestors of modern horses and camels, which survived for longer  because of their larger lung capacity. And finally, at the top of the deposit are  the site’s biggest animals, the rhinos.

And yes, there were rhinos and camels  living in North America back in the day! More than a hundred rhino skeletons  have been found at Ashfall. Although the ash was deadly to living  animals, it provided a nice soft bed for their remains, allowing their fossils to  be preserved in truly stunning detail.

Some skeletons are preserved in three-dimensions, exactly as they’d have been  when the animals were alive. And we even have impressions of some  of the birds’ feathers in the ashes. So this 12-million-year-old natural  disaster is now an incredible resource for scientists studying ancient  ecosystems in North America.

Volcanic ash can be great for preserving bodies, but it’s also awesome at preserving  other stuff, like footprints. In fact, some of the most famous  fossil footprints in the world only exist thanks to volcanic ash. We’re talking about the Laetoli Footprints, which were discovered in Tanzania in the 1970’s.

Paleontologists have found  thousands of footprints at Laetoli, preserved in 3.6 million year old ash deposits. These tracks were left by a variety of animals, including elephants, giraffes,  birds, and even some insects. But by far the most famous  feature of the Laetoli ash beds are footprints that look  a lot like yours and mine.

Amid the many animal footprints at  Laetoli, researchers discovered about 70 footprints left by human ancestors. The footprints were most likely  made by Australopithecus afarensis, which is the same species as the  famous Ethiopian fossil called Lucy. And the footprints aren’t  just from one individual.

We’ve got footprints from at  least three of these guys. Two of the trackways are side by  side, and a third individual followed. And what’s funny is that the third one  stepped directly into the larger footprints that were already there, but we have  no way to know why they did that.

To be clear, it’s impossible to know  whether these three were walking as a group or just all walked in  the same place at similar times. But we can learn a lot about how they walked. See, at the time these footprints were  found, we weren’t all that sure whether our earlier ancestors were walking upright on two legs or using their knuckles for  support, like chimpanzees.

So finding a bunch of footprints with no  knuckle-prints really was a smoking gun and helped answer a fundamental  question in human origins research. The Laetoli footprint site is like  a layer cake of preserved trackways. The Sadiman volcano, which is located  about 20 kilometers away from the site of the footprints, had a habit of  belching ash in bursts around this time.

An eruption would blanket the  area in ash, and later rainfall would turn that ash into  a sticky, cement-like mud. Our ancestors, along with other  animals, walked across that mud and left behind footprints that were quite  literally set in stone as the ash hardened. Then, the next eruption laid down more ash that covered and protected those footprints.

Millions of years later, erosion exposed the  footprint layers, and the rest is history. These ash beds are a treasure  trove of ancient information, but unlike other types of rocks,  these are really delicate. Anything from rain, plant roots, or even  the stomping feet of modern animals runs the risk of damaging these fragile pieces  of history, so when researchers aren’t actively studying the footprints,  they cover them with in layers of soil and sand for extra protection.

So at least in this case, erosion  giveth, and erosion taketh away. Now we’ve talked about what happens  when volcanic ash reaches areas pretty far away from an eruption, but now  let’s look at fossils that formed a little closer to volcanic ground zero. When you’re closer to an eruption, you’re  in danger of more than just falling ash.

You’ve got to worry about  things like pyroclastic flows. A pyroclastic flow is essentially an  avalanche of superheated ash, gas, and rock that cascades down  the slope of a volcano. These flows can reach temperatures  over 800 degrees Celsius, and they move fast, meaning you really don’t want to find yourself getting in the way of one.

And you’d think a pyroclastic flow would  just destroy everything in its path. And you’d be right, most of the time. But on some rare occasions, it can  also preserve really cool fossils.

When they cool down, these pyroclastic  flows form deposits called ignimbrites, which are kinda like pumice stone. One extraordinary ignimbrite  deposit comes from Rome, where scientists CT-scanned rocks from a 29,000-year-old ignimbrite and  found something unexpected. Staring back at them from the  scan was a vulture’s head.

Or rather, the space where  a vulture’s head had been. That pyroclastic flow had enveloped the vulture, and even though the actual bird  has long since decayed away, the ignimbrite ended up preserving  a perfect impression of its head. And this impression is stunningly detailed.

It preserved the shape of the  bird’s tongue and eyeballs, and even an impression of  its transparent third eyelid. And If this sort of pyroclastic  preservation sounds a little familiar, it might be because it’s similar  to what happened at Pompeii. But this vulture head is preserved with  way more detail than anything we’ve found at Pompeii, and that might be  because the pyroclastic flow that hit this vulture wasn’t as  hot as a typical flow would be.

Scientists estimated that this  pyroclastic flow had cooled to under 100 degrees Celsius by the time  it buried our little vulture friend. And while I wouldn’t exactly call  near-boiling temperatures cold, that ash flow wasn’t hot enough  to burn everything on contact, so soft tissues were able to  be preserved within the ash. Now, fossils in ash and rocks are one thing.

But surely there can’t be any  fossils preserved in lava, right? Any plant or animal remains caught in a lava flow would certainly be instantly destroyed. Well, let me introduce you to the Blue Lake Rhino.

Blue Lake is located in the state of Washington, alongside cliffs of basalt rock formed  from the cooled lava of ancient eruptions. And within those cliffs is an unusual cave. When people first found this  tiny cave in the early 1900s, they noticed that there were  some fossil rhino bones inside.

And when they went back to study the bones, the researchers noticed something  weird about the cave itself. It seemed suspiciously…. rhino-shaped. And it turns out that yes, the “cave” is  really an impression of a rhino’s body, preserved thanks to flowing lava.

Of course, something like  this doesn’t happen every day. The rock in this site is called pillow basalt, which forms when lava touches  water and cools really quickly. Around 15 million years ago,  lava flowed into the water, enveloped the rhino, and cooled into solid basalt.

Eventually, the rhino’s soft tissue rotted  away, leaving behind a rhino-shaped hole. Fortunately for the rhino, researchers  think that it was already dead when it became engulfed in  lava, and might have just been bobbing in the water until  that lava flow came along. And there are other log-shaped caves  nearby, leading researchers to think they were made when that lava  hit trees floating on the water.

In any case, this rhino’s death cave is probably one of the coolest ways to  be entombed, like, ever. Now so far, we’ve seen body fossils  preserved in ash and even lava, and we’ve seen footprints in ash. But now get ready for dinosaur  footprints preserved in magma!

At the Jindong Formation in South  Korea, there’s a layer of igneous rock from the Cretaceous Period that contains  footprints belonging to sauropods. That’s the Brontosaurus-type of dinosaur. And some of the footprints  are up to three feet long.

There are also some footprints  preserved in ash here too, but the magma footprints are the real prize. And yes, footprints in magma might sound  strange for a couple different reasons. For one thing, animals can’t  walk across molten rock.

They’d burn their little feetsies. Or their big feetsies, in this case. And the other problem is  that I said magma, not lava.

You might remember from  geology lessons that lava is molten rock on the surface and  magma is molten rock underground. Because of these different environments, lava and magma form different types of  solid rock formations when they cool. And well, these dinosaur  footprints are preserved in a sill, which is a horizontal band of igneous  rock that forms from the underground flow of magma, meaning that these  rocks formed underground!

And no, we don’t think these dinosaurs  were spelunking in magma flows. So here’s what we think happened  based on the geology of the site. The animals walked across mud and  left behind all their footprints, which then got covered up  and filled in by fresher mud, quick enough to preserve a ton of detail.

And with enough time, those muddy  layers solidified into rock. The lower rock layer has the actual  footprints in its upper surface, and the upper layer has the natural molds of those footprints sticking off the lower surface. And over time, magma seeped in  between these mudstone layers, and conformed around the casts of the footprints.

The magma eventually cooled and hardened, preserving the shape of the original  footprints on the upper surface of the sill. Eventually, the mudstone eroded away, but  the sill was more resistant to erosion and stuck around, exposing these  impossible magma-footprints! Now even though these are magma  copies of the original footprints, they’re preserved in immaculate detail, and we can even see details of the  toes and claws of the dinosaur’s feet.

So voila! Magma tracks! So these are just a few of the times  where the destructive power of volcanoes has ended up saving stuff that would  have otherwise been lost to time.

Which is super exciting to researchers,  even if it was kind of a bummer for the animals who had to go through it all. At least, except for that Blue  Lake rhino, which was already dead. [♪ OUTRO]