Scientists have tried for so many times to figure out how living things survived a glaciation event, which is commonly known as the Cryogenian Period.
The Earth is that era, which is also known as the Snowball Earth, lasted from 720 to 635 million years ago. And, as you probably thought, a layer of ice over the ocean would cut off the oxygen supply and would have delayed the animal life, but some fossils show that this was not the case whatsoever. It seems that life survived, then bloomed in the Cryogenian Period.
As per new research, this was all possible due to the meltwater from the glaciers that created oxygenated pockets in the oceans. In these “caves,” chemosynthetic life was able to wait for the ice age to emerge, and then to continue its growth.
How Life Survived the Snowball Earth
The pieces of evidence show that, even if much of these oceans during this sleep freeze would have been derelict because of the lack of oxygen, in the areas where the grounded ice sheet started to float, there was a supply of oxygenated meltwater. This could actually be explained by a glacier oxygen pump, which is described by air bubbles that are trapped in the glacial ice, and which are released into the water when it melts, thing that makes it full of oxygen.
Even if the fossil record from that period is very sparse, there are many geological traces of the conditions that were on Earth at that time.
The sediments were deposited on the seafloor, especially those that were rich with iron. This aspect allowed the team behind the study to reconstruct the oxygenation levels. But before this, scientists assumed that life held out in meltwater puddles on the surface, but what the team found now shows another way of things.