The Snowball Earth Period: An Overview

The Snowball Earth period refers to a time nearly six hundred million years ago when our planet was entirely covered in snow from pole to pole, marking one of the most severe ice ages in Earth’s geological history.

Life's Survival Strategies during Snowball Earth

• Geobiologists theorize that there might have been a broader habitable zone north of the tropic of cancer . Earlier, this area was considered too cold for life to exist.
• Climate models provide an explanation for the expansion of snow cover from pole to pole using simple feedback loop mechanisms.
• As the temperature drops, Earth's ice cap expands. Through albedo , the ice cap reflects sunlight, causing the ice cap to further spread.
• If the ice cap successfully extends to a 30-40 degree latitude, the entire Earth will be covered in ice within a few centuries.
• Earth has experienced two such periods in its geological history, with the most recent being the Marinoan Ice Age , which occurred between 654 and 635 million years ago.
• During the Marinoan ice age, life existed only in the seas as large creatures had not yet evolved. However, there is fossil evidence that suggests the existence of microscopic eukaryotes such as algae before and after this period.
• A study of thin shale from South China, dating back to the Marinoan period, reveals that the area was not covered with ice and photosynthetic organisms flourished there.
• Some scientists propose that fossils could be from microscopic algae that survived in small, shallow freshwater pools on top of glaciers . This theory is supported by the fact that all modern-day algae descended from freshwater species, suggesting that during the Snowball period, they were eradicated from the sea and later re-evolved.
• Another theory suggests that the equator was frozen only for a brief period during the Marinoan era.

The Cause of Snowball Earth

The consensus among scientists is that the formation of Snowball Earths is linked to the balance between incoming sunlight, the ice-albedo feedback, and the global carbon cycle.