Colliding Continents in the Tropics Likely Caused Ice Ages

(CN) – When large land masses collided with each other near Earth’s equator 80 million years ago, the aftermath resulted in tectonic pileups that eventually formed the Himalayas. But a new study published Thursday found exposed oceanic rock had such a strong chemical reaction when it jutted up into the tropical environment that it triggered three ice ages.

Long before the familiar land masses settled into place on Earth’s surface, there were supercontinents that drifted and collided into each other.

Each time these large land masses collided near the equator Earth experienced an ice age, according to the study published in the journal Science by researchers from the Massachusetts Institute of Technology, University of California, Santa Barbara, and the University of California, Berkeley. 

Tectonic pileups exposed the calcium and magnesium in oceanic rock, which reacted to the carbon dioxide in the atmosphere and cooled global temperatures millions of years after the collision. The ultimate result? An ice age, according to the study’s authors.

According to Oliver Jagoutz, an associate professor at MIT, the area of oceanic rock exposed near where the Himalayas are now ranged from 1 million to 5 million square kilometers – a large piece of land but miniscule when compared to a supercontinent.

Over a million years, the oceanic rock pulled out enough carbon dioxide from the atmosphere to affect the climate, as the gas was stored away in limestones along these stretches of land.

“But in reality, it’s a very thin strip of Earth, sitting in the right location, that can change the global climate,” said Jagoutz.

Two collision points formed when the supercontinent Gondwana moved north and collided with Eurasia, eventually forming the Himalaya range in present-day Asia. The first collision 80 million years ago and the second 30 million years later created sutures in tropical zones near the equator.

The researchers believe the rate which exposed the oceanic rock of the sutures reacted to carbon dioxide in the tropics was likely the trigger point that started an ice age – and was likely the reason the ice ages ended as well. Millions of years later, the oceanic rock weathered away and gave way to rock that stored less carbon dioxide, thus allowing the climate to warm up again.

The study went back further, exploring about 540 million years of geographic data models reconstructed to look at suture collision points, their dimensions and where they formed. Three collisions that were mapped showed each one was followed by an ice age. Furthering their hypothesis, the researchers found other continental pileups that occurred outside of tropical zones did not trigger a cool down in the Earth’s climate.

One suture point about 10,000 kilometers is still active today in Indonesia and is likely responsible for the current glacial period and ice sheets at the poles. This region of exposed oceanic rock is one of the most efficient areas on Earth for storing away carbon dioxide, according to the study’s authors. 

Jagoutz said efforts to try and replicate this natural chemical reaction on a human timescale to address climate change induced by humanity’s carbon emissions would be challenging at best.

“The Earth does this in a slow, geological process that has nothing to do with what we do to the Earth today,” said Jagoutz. “And it will neither harm us, nor save us.”

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