Things that make you go 'Boom!'.

**RECAP** Yesterday I talked about stuff.

About 550 million years ago, Earth underwent a drastic change. There was a change in the climate so severe, it makes todays climate change look like a joke. But, that's a story for another oddities post. Today, we're looking at the changes underwater. Because, at this time, there was nothing above water. Dirt was still being formed by our friends, the cyanobacteria. Their little corpses would wash up on shore and rot, then wind would pick up the remains and move them inland where the remains mixed with minerals eroded from exposed stone. Continue for billions of years and, SOIL!

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But underwater, you'll remember we had lot's of insignificant creatures that didn't do much but filter food from the water.

But with the dramatic change to the Earth, came an underwater change known as 'The Cambrian Explosion'. This marked the first time creatures really started to evolve into something you wouldn't recognize, but could easily see.

For a long time scientists thought this was when life began. (Richard Sprigg didn't find the first Ediacaran fossils until 1946). Their reasoning was sound: the rock layers showed nothing, then BOOM! fossils everywhere. Today, the prevailing thoughts are that all the Cambrian fauna were there in the Proterozoic, but were just to small to leave visible fossils.

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In 1910, geologist Charles Walcott was wandering the Canadian Rockies up in British Columbia. He stumbled on a fossil unlike any he had ever seen. It was contained on a piece of shale, and it appeared it had fallen down the hill form a site close by. Eventually, he had a team of diggers finding some of the strangest fossils ever seen. This location is now known as the Burgess Shale.

The seas of the Cambrian were much different then they are today. Most of the landmass had coalesced into one called Gondwana.

Since the Burgess Shale was found, several other sites of early Cambrian fossils have been found, most notably Chengjiang China.

Today has been full of background information. Tomorrow, we'll start looking at some of the downright odd creatures that really got life up and running on Earth. Creatures like, Anomalocaris, Opabinia, Waptia, Hallucigenia. Have a couple of teaser pictures of what the seas of the Cambrian may have looked like.

See you tomorrow with lots of the oddest arthropods you'll ever see.