New study explains how ‘Snowball earth’ sustained life
Snowball earth is the phase in earth’s history when all the lands and oceans were covered in ice from the polar to the tropical regions. This phase stretches across two ice ages from about 720- 635 million years ago to half a billion years ago. During this period, the ice sheet cut off the ocean from the atmosphere and sun- both of which are vital for sustaining life. During this period life on earth was confined to the oceans. Recent studies explain how the ocean received oxygen to support the life forms. It proposes that the oxygen rich streams flowing under the ice sheets close to the continents’ edges seeded in the necessary oxygen. The melt-water streams took in bubbles of oxygen from the ice into the marine environment. This was concluded from the fact that the rocks from this period (in places like California’s Death Valley, Namibia and Southern Australia) show rusts which is the oxygenated form of iron. These rocks which were previously under water showed higher levels of rusting when they are from locations closer to land than far out in the oceans. Their closer location to land implies higher oxygen exposure from these melt-water streams.