Tag Archives: Volcanoes

The Never-Ending Winter: The Snowball Earth Hypothesis

The history of the planet Earth will always be a mystery that many geologists strive to figure out. In one of my earth and ocean science courses this semester, we talked about the possibility of a Snowball Earth. When I first heard the name, Snowball Earth, I was confused as to what a snowball earth is and why scientists call it that but as the professor began explaining the concept, it became clear.

The Snowball Earth Hypothesis suggests that based on the rock record, the Earth was mostly or entirely covered by ice at certain points over a period of billions of years. Throughout most of the continents today, geologists have found dropstones which are a type of glacial deposits that suggest the presence of ice.

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Glacial Dropstone Source: Michael C. Rygel (WIkimedia Commons)

Dropstones are formed when glaciers move across the land and scratching the surface resulting in the collection of rock pieces. These pieces then combine together and are eventually dropped as the ice melts onto land or into the ocean and are eventually covered by sediments and turned to rock. As these dropstones form, the magnetite particles in the stones reflect the direction of the magnetic field. As a result, geologists have concluded that some of these glacial dropstones were formed at the equator.

Although hard to believe that the Earth can be covered in ice, several factors may have enabled the Earth to be cold enough to have ice at the equator. The first factor was that the sun was not emitting as much energy in the past and therefore the Earth was receiving less heat. Secondly, due to intense rainfall, the CO2 in the atmosphere are drawn down by the rain due to chemical weathering leading to a drop in temperatures.

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Quelccaya Glacier Source: Edubucher (Wikimedia Commons)

As temperatures drop, the polar ice caps start advancing towards the equator. As the amount of ice increases, the albedo effect becomes stronger leading to lower temperatures. At this point, I was thinking, how does this make sense since we are not living in igloos today? Well, the answer to that are volcanoes.

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Mahameru Volcano Source: Jurema Oliveira (Wikimedia Commons)

Due to the heat generated by the magma, volcanoes are able to melt through the ice and release many types of gases into the atmosphere such as CO2 and methane. These gases are important because they trapped heat and led to the end of the Snowball Earth. Therefore, over millions of years, these gases accumulated and eventually, the planet was hot enough to melt the ice within thousands of years.

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Source: Big History Project (Youtube Creative Commons)

Although not all scientists believe in the Snowball Earth, I found this theory to be a good example of what science is about. By looking at rocks underneath the ground and with the knowledge about how certain types of rocks form, geologists were able to hypothesize such an extreme event that occurred before humans walked the planet.

Adrian Li