Sedimentary structures encountered in South Australian rocks indicate that parts of the sea in which they were formed were open, and therefore unfrozen, during at least part of the Cryogenian, or ‘Snowball Earth’.
The term Snowball Earth is often used to describe a period about 700 million years ago when glaciers covered the planet.
Some researchers claim that even the surface of the oceans was completely frozen during this time, stopping oxygen release from the oceans and potentially even slowing down evolution. New results, published in Geology, show that seas around Australia were unfrozen at least for some time during the Snowball Earth period, refuting the idea that the planet was completely wrapped in ice at the time.
© Stefan Engels | www.bitsofscience.org