The Snowball Earth Hypothesis, Introductory Course

About this programme

Seven hundred and sixteen million years ago everything stopped. The seas stood still. Rivers did not flow. Temperatures plummeted. The entire world fell into silence as it was buried beneath snow and ice. There was one giant landmass at that time – a supercontinent called Rodinia. That supercontinent straddled the equator and, crossing its interior, a vast chain of mountains was rising up from the plains, forced upwards by geological forces. There were no land plants back then. Their emergence would happen hundreds of millions of years later. This meant that, before the snow began to fall, Rodinia was completely barren. Its landscape was one of wind-scoured rock surfaces amidst endless deserts. The barren surface of that supercontinent was highly reflective (mirror-like) and most of the sunlight that reached it would have been reflected back into space. This mirror-like behaviour is called the albedo effect. It cools the Earth. And, back then, it did so effectively, because Rodinia was positioned where Earth receives most sunlight – at the equator. And as the Earth became cooler, snow began to fall. And as snow fell, the whitened surface of Rodinia reflected even more sunlight back into space. The albedo effect was strengthened and the Earth cooled some more. And more snow fell. And the albedo effect became even stronger until a tipping point – a point of no return – was passed and not only Rodinia but also the oceans that surrounded it froze over entirely. This was Snowball Earth . Everything stood still for fifty-eight million years.