A volcanic event that took place on Earth nearly 170 million years ago triggered a massive ice age during the Jurassic period, researchers from the University of Exeter reveal in a new study. Compared to today's changing climate, which is mostly triggered by rising CO2 emissions, this large-scale volcanic event known as the North Sea Dome likely lasted millions of years and altered the flow of ocean water and the heat that it carried from the equator to areas in the North Pole. 

"We tend to think of the Jurassic as a warm 'greenhouse' world where high temperatures were governed by high atmospheric carbon dioxide contents. This new study suggests that re-organization of oceanic current patterns may also have triggered large scale climate changes," Professor Stephen Hesselbo, one of the study researchers from the Camborne School of Mines, based at Exeter's Penryn Campus in Cornwall, explained in a news release. 

During the Jurassic Period only one "supercontinent" called Pangaea covered the Earth's surface. This large land mass had a broad seaway across it that connected a north polar sea to a warm equatorial ocean, called Tethys. For their study, researchers spent 10 years analyzing seawater temperature change data evident in fossil mollusc shells. This revealed that the North Sea Come event coincided with significant and fast-cooling global temperatures. 

Therefore the team suggests this volcanic event changed the flow of ocean water and its associated heat, flipping the northern hemisphere from a very warm climate to a cold climate state. It follows then this cold period would have lasted many millions of years, until the North Sea Dome subsided.

"Although we have known about the occurrence of cold periods during greenhouse times for a while, their origins have remained mysterious," Professor Hesselbo added in the university's release. "This work suggests a mechanism at play that may also have been important for driving other climate change events in the Jurassic and at other times in Earth history." 

Their study was recently published in the journal Nature Communications. 

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