Snowball Earth [UPSC Notes]

A new study has thrown light on ways and possibilities of the survival of sea life during the snowball Earth period, which has been a mystery so far. What is the Snowball Earth period? What caused it? Read on to know more about snowball earth. This topic is relevant for the IAS exam geography segment.

What is the Snowball Earth Period?

Snowball Earth is a period before six hundred million years when the earth was covered with snow from pole to pole and it is considered an inhospitable period in Earth’s geological history.

How did organisms survive?

• Geobiologists opine that there is a possibility of the existence of a wider habitable zone in the north of the tropic of cancer. It was previously assumed as a very cold zone and life didn’t exist in this zone.
• Climate models explain the spread of snow from pole to pole through simple feedback loop mechanisms.
• Initially, when the temperature drops, the ice cap of the earth will expand and through albedo, the icecap will reflect sunlight leading to the spread of the icecap to more areas.
• If the icecap successfully penetrates 30-40 degree latitude, within a few hundred years the icecap will cover the whole of the earth.
• Earth experienced two such periods in its geological history and the most recent such period is called Marinoan Ice Age, between 654 million and 635 million years ago. 
• During the Marinoan ice age life existed only in seas and large creatures were yet to evolve. However, certain fossil evidence points to the presence of microscopic eukaryotes such as algae before and after the period.
• Researching a thin shale in South China that belongs to the Marinoan period shows that the area where the shale was found was not capped with ice and photosynthetic organisms thrived in the area.
• However, some scientists also suggest that fossils could be from microscopic algae that survived in tiny, shallow pools of freshwater at the top of glaciers. All modern-day algae descended from freshwater species which suggests that during the Snowball period, they were wiped from the sea and re-evolved later.
• There is also another view that the equator was only frozen for a short period of time within the Marinoan period.

What caused Snowball Earth?

Scientists generally agree that the formation of Snowball Earths has something to do with the balance between incoming sunlight, the ice-albedo feedback, and the global carbon cycle.

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