When Earth was a frozen Snowball (BBC)

[eppur_se_muova]

Presented by
Kate Ravilious

The ice brought Earth to a standstill. Where there were once waves lapping onto a tropical shore and warm waters teeming with life, there was just the whistling of the wind and a cold barren landscape, covered in ice as far as the eye could see. Even at the equator – the warmest place on Earth – the average temperature was a frigid -20°C, equivalent to modern-day Antarctica. Most life was wiped out, and the creatures that did survive huddled in small pockets of open water, where hot springs continued to bubble up.

This was "Snowball Earth" – a deep freeze that began around 715 million years ago and held Earth in its icy grip for a good 120 million years. "There are no other comparable glacial periods on Earth. This one was really quite catastrophic," says Graham Shields of University College London in the UK.

However, some scientists now believe that this crushing catastrophe drove one of the most incredible steps in evolution: the development of the first animals, and a dramatic flourishing of life known as the Cambrian explosion.

Around 540 million years ago, a host of exotic creatures suddenly appeared. They included giant woodlouse-like creatures known as trilobites, the five-eyed Opabinia, and the spiny slug-like Wiwaxia. Suddenly, Earth leapt from being dominated by single-celled bacteria to a world teeming with exotic multicellular creatures, all in a geological blink of an eye.
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http://www.bbc.com/earth/story/20150112-did-snowball-earth-make-animals




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