Within a geological blink on an eye, a span of only 10 million years, the number of species on the planet tripled. This exotic phenomenon took place within a 40-million-year florescence of life, unlike any before or since known as the Great Ordovician Biodiversification Event, the biggest expansion of biodiversity in Earth’s history.
In the Ordovician almost the entire top of the globe was a vast ocean. Much of the living world was jammed onto shallow seas. Reefs, writes Peter Brannen in Ends of the World, began to grow in tiers and complexity, larvae took to the surface waters to avoid the gauntlet of tentacles on the seafloor, and animals began to burrow deeper in the muck to avoid the menace of squidlike monsters and giant sea scorpions the size of a human being.
One fascinating theory suggests that Diversity’s Big Bang is owed to a great collision in outer space 470 million years ago –the largest documented asteroid breakup event. In the vast empty spaces between Mars and Jupiter, an immense, soundless collision destroyed an asteroid more than 100 kilometers in size, sending mile-long shards of the wreck swirling through the solar system.
It was the largest asteroid breakup in billions of years. For a few million years afterwards, the earth absorbed the scattershot fallout from this collision in a hail of asteroids, one of which put an abrupt end to the age of dinosaurs.
A 2008 Nature Geoscience paper argued that this Ordovician barrage from smaller rocks might have actually jump started the epoch, electrifying biodiversity by disrupting biocommunities, clearing up ecospace, and just generally shaking things up. The enormous sea scorpion, writes Brannen, was found in Iowa was discovered living in the watery ruins of one such crater dating to around 470 million years ago.
Other craters of the same age are found in Oklahoma, in Wisconsin, and on the Slate Islands in Lake Superior. Across the globe, meteorite materials in Sweden, Russia, and China all similarly date to around 470 million years ago. Even today, most earthbound meteorites come from the swarm of debris created by this massive primeval collision. It should be stressed that this was not the only reason why diversification occurred at the time: other epochal changes such as a dramatic surge in Earth’s oxygen levels in air and water reaching near modern levels, as well as ocean cooling, increased nutrient supply in the oceans and predation pressure.
But as with as evolutionary ages, this world was doomed. In the closing chapters of the Ordovician, 85 percent of life on Earth would be wiped out.
The Daily Galaxy via Ends of the World and The Atlantic
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