Rocks dating back to the Snowball Earth era indicated that the transition to global icing could occur incredibly quickly.
Scientists suggest that the Earth has been completely (or almost completely) covered with ice several times in its geological history. This is evidenced by glacial deposits of different eras, reaching very low latitudes, and an excess of carbon-13 in the rocks of that time, indicating the absence of photosynthesis, and paleomagnetic data. Princeton geologists investigated such samples found in Ethiopia and formed during one of the periods of the "Snowball Earth", during the Sturtian glaciation of the cryogenic epoch - about 717 million years ago.
In an article published in the journal Geology, Scott MacLennan and his colleagues showed that the diamictites they studied - fragments of powerful boulders transported by glaciers over long distances - are of glacial origin. Below they gradually pass into the more ancient layers of carbonates: this suggests that previously such an area was shallow water, rich in marine microflora.
Such a picture, according to scientists, indicates that in the era of the death of the supercontinent Rodinia, the region turned from a humid and blooming tropical paradise into an icy desert. Judging by the lack of a clear boundary between glacial and shelf deposits, the transition occurred gradually, albeit extremely quickly: McLennan et al. Indicate the interval from 1000 to 100 thousand years.
This is a surprisingly short time, which can be explained by the action of a positive feedback between icing and an increase in the planet's albedo. The more it was covered with ice, the more solar radiation it did not absorb, but reflected into space with shiny white areas of the ice surface. And the more it continued to cool down, building up new glaciers, until it was completely covered by them - or almost completely.
Sergey Vasiliev