The Ends of the World: Volcanic Apocalypses, Lethal Oceans, and Our Quest to Understand Earth’s Past Mass Extinctions
(c) 2017 by the author
When one reads essays in the right places, one finds mention of how we are in the sixth great “mass extinction”. Humans seem to be wiping out species left and right, through habitat destruction even in cases where we aren’t really trying. Brannen takes a look at the other five, and extracts lessons for today.
For the record, the “Big Five” are the Late Ordovician, Late Devonian, End Permian, Late Triassic, and the Cretaceous-Tertiary Event. In comparatively short time frames, the vast majority of species – both plant and animal, on land and in the water – were erased from the planet.
You might think that you’d have to go to the ends of the world to find the fossil evidence. After all, isn’t the famous Burgess “Cambrian Explosion” Shale in remote Canada, aren’t those big dinosaur digs all out in the badlands of the American west, and to find dinosaur eggs you need to be out in the Gobi Desert? Well, if that’s what you want, sure. But Cincinnati sits atop a half-billion year old sea bed. Fossils from the Devonian (400 million years ago) practically fall out of highway cuts around Cleveland. And the Palisades of New Jersey? Those are the lava flows from the end of the Triassic (200 million years ago).
Brennan travels around those parts of the United States, talking to geologists, paleontologists, and fossil hunters to discover – and explain in a clear and friendly manner – just what the heck happened to wipe out so much life.
You’ve all seen those “clocks” or even “calendars” that condense all of Earth’s history into one day or one year. They’re intended to show just how little of Time is taken up by recorded history. Those are OK, I suppose, but it’s kind of hard to get a real sense of the scope of geologic time. We’re not that good when it comes to visualizing Time.
One of the scientists that Brannen meets has a different idea. Let one step equal 100 years. We’re better at visualizing distances, so why not?
You can easily shake hands with George Washington, Thomas Jefferson, and all the other Founders. You can wave to Jesus and Julius Caesar across the street. Heck, all of recorded history is within easy shouting distance.
How about geologic time?
Let’s start in midtown Manhattan. Doesn’t really matter where. Start walking. By the time you reach the Hudson River, you’re surrounded by Neanderthals. Newark is filled with Australopithecines. Want to see dinosaurs? Keep walking until you reach Washington DC. The Great Permian-Triassic Extinction happens around the Indiana-Illinois border. LIfe’s first tentative steps onto land appear when you reach Colorado….
It’s never as simple as a killer asteroid from space. Even the one that “killed off” the dinosaurs at the end of the Cretaceous had help. And the extinctions occurred over hundreds of thousands of years – at least. Brennan does his best to tease out those factors relevant to the modern era. Climate change. Carbon dioxide in the atmosphere and ocean acidification. Invasive species even get a passing nod.
The tone is generally light. No “doom and gloom” here. The people he meets and talks with all come across as being happy and excited about their work. And we are introduced to so many amazing creatures. Like the crocodilians of the Triassic. And the terror of the Devonian seas, the Dunkleosteus. It flourished at the same time fish were creeping up onto land, leading Brennan to speculate that the reason for their getting out of the water was that they were desperately fleeing one of the scariest predators ever….
Brennan is careful to note in his last chapter, on the Modern Era and the sixth “great extinction”, that even as bad as things look today, we’re nowhere near as disastrous as with the earlier ones. The Earth is past the era of massive vulcanism of the sort that created the Siberian Traps, and we are taking the threat of asteroid impact seriously. Those earlier extinctions saw something like 50%-90% of all species get wiped out. Today, we’re seeing less than one percent. The Earth will be fine. Life will be fine.
Humans, on the other hand….
(More on the Big Five here.)