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BOSTON, April 19 (UPI) -- Researchers have known that across the great expanse of Earth's geologic history, tectonic shifts and climate change are linked. Identifying more specific correlations -- cause and effect -- has proven difficult. However, new research shows tectonic activity likely triggered the last two ice ages.
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"I think we're the first ones to really link large-scale tectonic events to climate change," Oliver Jagoutz, associate professor of planetary sciences at MIT, said in a news release.
The tectonic activity researchers say is responsible for Earth's last two cooling periods involved the movement of the supercontinent Gondwana northward from the Southern Hemisphere toward Eurasia. Between 300 million and 180 million years ago, as Gondwana inched toward the equator, it broke up into the continents we know today -- Antarctica, South America, Africa, India, and Australia.
As Gondwana's fragments first bumped up against Eurasia, an uptick in volcanic activity resulted in higher amounts of CO2. But eventually, an oceanic plate between them, the Neo-Tethys Ocean, was pushed onto the continent, snuffing out the volcanoes.
This tectonic activity, researchers say, resulted in new rocks -- basalts and ultramafic rocks -- being exposed to the tropical elements in large quantities. When exposed to warm temperatures and heavy rains, as tends to happen near the equator, these types of rocks host chemical reactions that can pull CO2 from the air.
Researchers believe that as the oceanic planet was exposed, these oceanic rocks served as a massive carbon sink. As carbon was pulled from the atmosphere, temperatures dropped and an ice age began.
This happened first some 80 million years ago, as northern Africa collided with Eurasia. Another ice age was triggered 50 million years ago when India hit Eurasia.
"What nature shows us is, if you put a lot of these rocks in the tropics, where it's hot, muggy, wet, and rains every day, and you also have the effect of removing the soil constantly by tectonics and thus exposing fresh rocks, then you have an excellent trigger for ice ages," Jagoutz explained.
The findings, published in the journal PNAS, are also an example of the Earth's innate ability to balance out climatic change.
"To confidently estimate the long-term fate of fossil fuel carbon in the atmosphere, we need to fully understand the dynamics of the carbon cycle and how it operates on all time scales," said study co-author Lee Kemp, a professor of geosciences at Penn State.
"This study highlights an important restorative force of the carbon cycle," Kemp added. "The 'repair mechanism' for volcanism-induced warming is the chemical weathering of the volcanic rocks themselves -- a repair job that takes millions of years."
