Escaping from Snowball Earth
In this video, Dr Ernest Chi Fru explains how Earth managed to escape from Snowball Earth ice ages.
The end of Snowball Earth ice ages is thought to have been triggered by an increase in the levels of the greenhouse gas, CO2 in the atmosphere. High levels create the so-called greenhouse climate we experience today, and low levels are typical of ice ages.
CO2 as Earth’s thermostat
The level or amount of CO2 in the atmosphere is thought to regulate Earth’s climate. Sunlight penetrates the atmosphere and heats up Earth’s surface.
But it is CO2 in the atmosphere that effective regulates the amount of heat from sunlight that is reflected back to space. CO2 absorbs and conserves that heat, just like a sponge absorbs water.
Consumption of CO2 via weathering
Volcanoes can increase the levels of CO2 in the atmosphere, but it is the the wearing away of calcium silicate (CaSiO4) rich rocks by CO2 that removes it from the atmosphere. This process is called weathering.
It is thought that Snowball Earth’s happened suddenly and were caused by rapid weathering that effectively sucked CO2 out of the atmosphere.
The greater the number of fresh rocks that can be weathered by reacting with CO2, the lower the amount of CO2 in the atmosphere and the greater the amount of calcium carbonate (CaCO3) buried at the bottom of the sea.
Weathering increases with temperatures, this is why soils along the equator are the most weathered on Earth compared to soil in the temperate regions.
The reaction between CaSiO4 and CO2 works like a thermostat that regulates Earth’s temperature and climate.
Summary
Looking at how our planet escaped Snowball Earth helps us to understand our climate now and the crucial role CO2 in the atmosphere plays.
The balance between the production of CO2 and its consumption via weathering is crucial for regulating a climate that can support life.
Just as we need oxygen in the atmosphere to have a planet that is habitable, we also need CO2 as without it the planet would be inhospitably cold.
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