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Volcanic islands in Alaska’s Aleutian chain might be part of a single, undiscovered giant volcano. If correct, the discovery of a single volcanic caldera would place it in the same category as the Yellowstone volcano responsible for some of history’s most violent super-eruptions.

The Islands of the Four Mountains in the central Aleutians is a tight group of six stratovolcanoes.

Everything we look at lines up with a caldera in this region

Dr Diana Roman

These all boast steep conical shapes and have all exhibited evidence of previous powerful eruptions.

One of those studied and the most active of the chain, Mount Cleveland, has generated several pieces of evidence indicating the islands share a single interconnected caldera.

Stratovolcanoes usually tap small or modestly-sized reservoirs of magma, whereas calderas are conversely formed by tapping far larger reservoirs in the Earth’s crust.

When the reservoir’s pressure exceeds the crust’s strength, enormous quantities of lava and ash are spewed in a catastrophic eruption.

The proposed caldera underlying the Islands of the Four Mountains would be even larger than the nearby Okmok volcano.

Experts now suggest Okmok was involved in the disruption of the Roman Republic when it erupted in 43 BC.

According to geophysicist Dr Diana Roman of the Carnegie Institution for Science, the discovery could become the first caldera found hidden underwater in the Aleutians.

Dr Roman, who co-authored the study, said: ”We’ve been scraping under the couch cushions for data.”

She added: ”But everything we look at lines up with a caldera in this region.”

Despite tantalising evidence, Dr Roman and the study’s lead author John Power, a researcher with the US Geological Survey (USGS), caution the caldera’s existence is not yet confirmed.

The researchers would need to return to the islands to gather more direct evidence.

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Dr Roman said: ”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.”

However, the researchers’ giant caldera theory does help explain the frequent explosive activity seen at Mount Cleveland.

This is widely considered the most active volcano in North America for the past two decades.

Mount Cleveland frequently spews ash clouds as high as 15,000ft and 30,000ft into the atmosphere.

Such eruptions routinely pose hazards to aircraft travelling the busy air routes between North America and Asia.

Dr Power said: ”It does potentially help us understand what makes Cleveland so active.

“It can also help us understand what type of eruptions to expect in the future and better prepare for their hazards.”

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