A group of volcanoes in the northern Pacific might actually be separate vents of a single supervolcano capable of immense destruction, scientists have revealed.
The six volcanoes - Carlisle, Mt Cleveland, Herbert, Kagamil, Tana and Uliaga - are located in the Aleutian Islands chain off the coast of Alaska. Each is presently considered a stratovolcano - the stereotypical cone-shaped mountain with a crater at the top, like Mt Taranaki.
Non-dormant stratovolcanoes erupt fairly regularly, with Mt Cleveland - named for the locals' fire goddess - particularly active, going off eight times in the past 11 years.
But scientists who've been studying Mt Cleveland - known as Chuginadak by locals, named for their fire goddess - suspect the six volcanoes are part of one interconnected caldera.
"We've been scraping under the couch cushions for data," said study co-author Diana Roman of the Carnegie Institution for Science in Washington. "But everything we look at lines up with a caldera in this region."
A caldera is formed when a volcano blows so hard, the entire thing collapses - Lake Taupō, for example, is the caldera of two massive eruptions - one that took place 26,500 years ago and the second about 1800 years ago. The first - known as the Oruanui eruption - is the biggest in the world known to have taken place in the last 70,000 years. The second, Hatepe, was no slouch either - the biggest of the past 5000 years.
A supervolcano is defined as one capable of an eruption measuring 8 on the Volcanic Explosivity Index. The last eruption this big was Lake Taupō's Oruanui eruption.
Other supervolcanoes include the Yellowstone Caldera in the US, which is capable of eruptions as big as Taupō and Lake Toba in Indonesia, whose eruption 74,000 years ago possibly came near to wiping out humankind.
"It does potentially help us understand what makes Cleveland so active," said John Power, a researcher with the US Geological Survey at the Alaska Volcano Observatory. "It can also help us understand what type of eruptions to expect in the future and better prepare for their hazards."
They hope to return to the remote site soon to confirm their theory.
"Our hope is to return to the Islands of Four Mountains and look more closely at the seafloor, study the volcanic rocks in greater detail, collect more seismic and gravity data, and sample many more of the geothermal areas," said Dr Roman.
The area is known for historically devastating eruptions - in 43BC an eruption at Mt Okmok, just to the east of Mt Cleveland, coincided with massive crop failures in Europe which have been credited with contributing to the end of the Roman Republic. That was only a 4 on the Volcanic Explosivity Index.
The evidence for the new supervolcano will be presented at a meeting of the American Geophysical Union next week.
