"Long before there were these things called supervolcanoes, we've known about giant, big, horrific silicic volcanic eruptions," said Seaman, of the University of Massachusetts at Amherst. The most massive of these blasts in recent history was Toba, which blew up an island in Indonesia 2.5 million years ago. The explosion heaved 700 cubic miles (2,800 cubic kilometers) of magma out of the Earth's crust.Around 420 million years ago, a series of super-eruptions dropped thick piles of ash and lava fragments along the proto-East Coast. There are at least four volcanoes spread out along 100 miles (160 km) of Maine's coast, Seaman said.
© Edwin Chase
Mount Desert Island in Maine's Acadia National Park as seen from across the Mount Desert Narrows.
Mount Desert Island in Maine's Acadia National Park as seen from across the Mount Desert Narrows.
Since they formed, the ancient volcanic layers have been tilted up by tectonic forces, providing a top-to-bottom slice through a supervolcano. For example, Isle au Haut, part of Acadia National Park, exposes the heart of a volcano. "The whole magma chamber is lying on its side," Seaman said.
Comment: The Jebel Zubair volcano also erupted in December 2011, resulting in the formation of a new island.