The word “Jurassic” usually calls to mind images of tropical Isla Nublar, with dinosaurs pottering about between humidity-drenched greenery. But hot weather wasn’t always the norm during the Jurassic Period. Around 170 million years ago, an ice age that lasted millions of years took hold—and a new study has found evidence that volcanoes were to blame.
At the time, the world consisted of a single supercontinent known as Pangaea, which was divided by a broad seaway called Tethys. Tethys connected the warm equatorial ocean to the north polar sea.
An international team of experts spent 10 years studying the change in seawater temperatures in this time period using mollusk shells that deposited in the seaway. They discovered that this cooling period coincided with a large-scale volcanic event out of what is known as the North Sea Dome in the oceanic corridor.
According to the paper in Nature Communications, this volcanic activity lifted up the dome, restricting the flow of Tethys around it and preventing the flow of warm water into the Arctic regions. Meanwhile, the cold Arctic waters were able to exert a stronger cooling influence in lower latitudes.
This dropped the temperature of the ocean water in the area by as 50 degrees Fahrenheit, and plunged the Earth into an ice age for millions of years, until the North Sea Dome finally dropped back down.
“We tend to think of the Jurassic as a warm ‘greenhouse’ world where high temperatures were governed by high atmospheric carbon dioxide contents,” said co-author Professor Stephen Hesselbo from the University of Exeter in a statement. “This new study suggests that re-organization of oceanic current patterns may also have triggered large scale climate changes.
“Although we have known about the occurrence of cold periods during greenhouse times for a while, their origins have remained mysterious. 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.”
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Feature Image: No, it’s not the North Sea Dome, it’s a volcano in South America. But you get the idea. (Credit: Thinkstock)
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