While taking Earth 002 last fall semester, we began talking about the Carbon Cycle. For those of you how don’t know, the Carbon Cycle is the process of carbon being transformed and used throughout the Earth system. It’s pretty simple. Carbon dioxide from the atmosphere is taken and absorbed by autotrophs in the ocean and on land through photosynthesis, then animals eat these primary producers, plants, and release CO2 through cellular respiration which goes back into the air and the cycle keeps repeating itself. I don’t want to be to technical because this class is for people who don’t like science, but that is the very basic version of a complex system. Below is a diagram just in case (or very likely) I didn’t explain it well enough. But one very important thing that you absolutely NEED to know is that CO2 helps regulate temperature. Why is this so important? Two words: Snowball Earth. http://www.visionlearning.com/en/library/Earth-Science/6/The-Carbon-Cycle/95
What Is Snowball Earth?
Snowball Earth is a theory that at one point in time very long ago, everything on the Earth was almost or entirely frozen. If you were to use a time machine and go take a snapshot of this from outer space, it would look like a giant snowball. A scientist from Australia first brought the idea up but his findings were mistaken by the geographic position of Australia. The idea emerged again by W. Brian Harland who had better evidence to back it up. The idea kept emerging and finally, the idea was named Snowball Earth.
What Caused Snowball Earth?
Remember that one important fact I said you absolutely needed to know? Well, in case you forgot, CO2 helps regulate temperature. There are records of a decrease in CO2 in the atmosphere causing the temperatures of Earth’s surface to drop. Therefore, due to a decrease in CO2 and a decrease in temperature, ice and snow became more abundant. Ice and snow reflect solar radiation therefore causing less CO2 to be absorbed into the atmosphere. This loop continues and there is essentially a disturbance in the Carbon Cycle. This causes the Earth to stay in this frozen state.
How Did the Earth Thaw?
There are many theories on how Snowball Earth. One theory is that clouds helped thaw the Earth. It is said that the clouds did this be heat trapping. As the solar radiation was reflected off of the snow, it is thought that the clouds helped trap the greenhouse gases from the solar radiation slowly the carbon cycle started to function properly again causing the planet to defrost. Another theory is that although CO2 was not being absorbed int he atmosphere, the theory of plate tectonics was still taking place under all of the frozen tundra. Through plate tectonics, CO2 can be released through the eruption of volcanoes both on land an under water. So through eruptions, CO2 was able to be released into the water and on land warming the Earth and sending the system out of its frozen state.
There are many more ideas but the truth is, we will never truly know how the Earth got out of its frozen state. In order to determine an actual cause, we would have to conduct an experiment which is highly impossible. There would be no way to determine causation leaving only theories to explain this phenomenon. All we know is that there was a disruption in the Carbon Cycle causing Earth’s surface to freeze over. What mechanism caused the disruption to occur or what caused the Earth’s surface to defrost are things that we will never truly never know.