The worst day in Earth’s history: The dinosaur extinction event.

kt event

Though they’ve been dead for 65 million years, dinosaurs are really hot right now, thanks mostly to the release of the popular movie Jurassic World. But then again dinosaurs have never gone out of style. Every few years they crop up again in popular culture, and as every new generation of 7-year-olds becomes fascinated by these real-life monsters their memory lives on. It’s very rare for me to do a post on pre-human history, but due to research I’m conducting on a class I’ll be teaching this summer on the history of climate change, I recently read some material on the great dinosaur extinction event–often referred to, in bloodless scientific terms, as the “K-T event”–and I was moved, disturbed and even horrified to a degree I did not expect. In thinking about what happened on one terrible day 65 million years ago, it seemed to me that a lot of the meaning and power of this event is usually lost in the antiseptic scientific way it’s retold. In this article, therefore, I thought it was worth putting up a few thoughts on one of the most dramatic and sad events in the history of the world.

You probably know the general outlines of the story. At the very end of what geologists call the Cretaceous Period, some large object from space–most likely a small asteroid–struck the Earth with incredible force. Various sudden changes related to the impact altered the world’s climate in a fairly short period of time, and very few of the millions of dinosaur species then existent on the Earth were able to adapt. All but the airborne dinosaurs–the ancestors of modern birds–went extinct. Small mammals, mostly rodents, were able to survive and adapt, and their evolution eventually began the age of mammals that resulted, fairly recently, in the development of humans. The remains of dinosaurs became coal beds, puddles of oil under the ground or fossils that now grace natural history museums. And the world moves on.

k-t boundary

The “K-T Boundary,” the geologic evidence of the great extinction, is plainly visible in layers of rocks like this one. It’s the same all over the world.

This shorthand explanation is fundamentally correct, but there’s a lot more to the extinction event than that. What struck me when I read about the extinction event is how sudden it was. The asteroid impact hypothesis was first proposed in 1980 by geologist Luis Alvarez, who noticed that in layers of rocks from that time there was a very thin dark layer of clay sediment, called the K-T Boundary. All dinosaur fossils are found below the K-T boundary, which is how we know they all went extinct (excepting the avian ones). Alvarez discovered that the K-T Boundary itself had high levels of iridium, an element usually associated in modern times with nuclear weapons, but which probably got there from some kind of astral impact. In 1990 researchers identified the likely place of impact: an old eroded crater off the coast of Mexico, called Chicxulub. Evidence discovered since 1990 has greatly bolstered Alvarez’s theory to the point where most experts now accept some version of it. Interestingly, scientists have begun identifying other large craters about the same age in various places around the world, suggesting that perhaps it wasn’t one asteroid that hit us, but a “shower” of debris from the skies.

Reading about the effects of the impact is absolutely chilling. Whatever day this happened, 65 million years ago, has every right to be called the worst day in the history of the world. Scientists estimate that the energy released by the asteroid impact was 7 billion times the destructive force of the nuclear weapon that destroyed Hiroshima. Just imagine that–7 billion Hiroshimas, in one place, in one instant, on one day. A gigantic volume of rock and water–the asteroid struck what was then a shallow sea–rose into the atmosphere in the wake of the impact, causing a colossal fireball that literally set a large part of Earth’s atmosphere on fire. Forests burst into flames instantly. Much of the rock fell back to earth in molten form, a rain of fire. About 20% of it vaporized and remained in the upper atmosphere, circling the Earth in a shroud of darkness and toxic doom. Global temperatures would have fallen immediately and stayed low for thousands of years. Whatever the high temperature was on the day the asteroid hit, it set a thousand-year record. Forget “Ten Years of Winter.” Imagine a thousand years of winter.

dinosaur extinction

Though the dinosaurs in this artist’s depiction are evidently fanciful, this painting comes close to communicating what the hell of the K-T Event must have looked like.

Here is something I didn’t know before: the asteroid impact and the strange particulates it threw into the sky caused a series of chemical reactions in the higher levels of the atmosphere. Various unusual chemical compounds were formed, most of them poisonous, falling to Earth as acid rain. With so much particulate in the air it would’ve rained a lot in the days after the disaster. The rain poisoned the surface waters of the world’s oceans, where most plankton live. Plankton is the foundation of the marine food chain. As plankton died, probably pretty quickly, the entire aquatic food chain collapsed, which explains why most aquatic species on Earth, including all swimming dinosaurs, also went extinct. The oceans became vast pools of poison lapping on shores of sizzling mud, under skies hazy and blackened with poisonous smog.

This all happened very fast. In fact, one recent hypothesis, popularized by the wonderful scientific performance art show Radiolab, suggests that this all could have happened in two hours. In two hours. I’m not sure I believe that all the dinosaurs on Earth were dead that quickly, but certainly many of them died that day the asteroid hit, and the death kept coming in the days afterward. We know from the fossil records that dinosaurs were thriving right up until that day. They had never been more successful, biologically or in terms of evolution, than they were at the very end. The asteroid annihilated them at the height of their glory.

In early 2014 “Radiolab” did a fascinating show on the dinosaur extinction. Here’s a portion of it.

I can’t help thinking about what Earth must have been like a few days or weeks after the asteroid strike. Imagine an entire planet shrouded in blackish dust, where the dawn, if it comes at all, is hazy and blood-red. The air smells foul like sulfur and smoke. Forests are long ranges of blackened stumps, some still burning. It’s cold, perhaps raining or snowing in many places, and the precipitation is toxic and burns everything it touches. Plants are wilted, mushy stumps. Everywhere are the carcasses of dead giants, rotting into moldering lumps, melting into the earth. The oceans are filled with floating corpses of animals, bobbing in waves of poison. Shorelines are littered with festering carcasses of dinosaurs, fish, birds, kelp, and all kinds of animal life. Maybe some dinosaurs still live, starving to death, rasping or writhing in their final agony. The world is filled with the stench of death and rot. No humans were there to experience it, but this could have been nothing less than a vision of Hell. And this is not a fantasy. It really happened.

Welcome to planet Earth.

All images in this article are in the public domain (I am not the uploader of the Radiolab clip).


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