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New research suggests a supervolcano left behind the crater shown here, which measures about 15 miles wide by 15 miles long.
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Ken Canning / Getty Images
Supervolcanoes in Maine?
Some of the biggest volcanic eruptions in Earth’s history may have happened on America’s East Coast

By Laura Leigh Davidson | for  

Did you know Maine was once home to some of the biggest volcanoes on Earth? These massive mountains were what scientists call supervolcanoes. Their “super eruptions” piled thick ash and lava that would harden and eventually become the East Coast, says geoscientist Sheila Seaman.

A geoscientist studies the makeup of planet Earth. Seaman’s research suggests that at least four supervolcanoes were located along a 100-mile stretch of Maine’s coast. She believes the volcanoes were last actively erupting around 420 million years ago.

“The coast is so serene [peaceful] and so beautiful and has such a terrible, violent past,” Seaman told LiveScience. Seaman presented her research on Maine’s monster mountains at the Geological Society of America’s annual meeting in October.

DIGGING INTO AMERICAN HISTORY

To learn more about Maine’s ancient volcanoes, Seaman dug into piles of volcanic rock in places like Isle au Haut, an island that’s part of the state’s Acadia National Park. On the island, Earth’s tectonic plates (gigantic, slow-moving rock slabs just below the planet’s surface) had moved enough to reveal the heart of one of these supervolcanoes, from which lava had once poured out.

Seaman says the rock she studied was very similar to rock found after other eruptions in the U.S. that formed calderas. A caldera is a bowl-shaped crater left by an erupting volcano, especially when the eruption leads to the collapse of the volcano’s mouth. (Much of Yellowstone National Park in Wyoming is a very big caldera.)

Her research suggests that in Acadia National Park, one caldera created by a supervolcanic eruption was about 15 miles long by 15 miles wide. That’s one big hole in the ground!

Now that Seaman has determined the existence of Maine’s supervolcanoes, she’s going to study what could have caused the enormous eruptions. One possibility is that different kinds of magma—hot, fluid material beneath Earth’s surface—mixed together and became unstable.