How an Antarctic volcano single-handedly kicked the southern half of the world out of an ice age

Mount Takahe rises up more than 2,000m above the ice sheet.USGS and NASA, LIMA

Ash, magma and toxic gases that erupted from a huge volcano in West Antarctica triggered a melting event that spread throughout the southern hemisphere about 17,700 years ago, scientists have said.

A series of eruptions of Mount Takahe over 192 years changed the climate from the South Pole to the sub-tropics, according to a study in the journal PNAS. Its eruption helped to warm the southern hemisphere out of the most recent ice age about 17,700 years ago.

Mount Takahe is a very large stratovolcano. Its summit sits across the ice sheet, and has a diameter of about 35 kilometres with a caldera measuring about 10km across, where the entire summit of the volcano collapsed into its centre during an eruption. The volcano has been active for a few hundred thousand years.

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Ice ages are determined by a range of planetary and climatic factors. Part of the equation is how much radiation the Earth gets from the sun, which depends on the tilt of the Earth and how this coincides with its position in the elliptical orbit. But large volcanic eruptions can also influence when a deglaciation happens.

Another factor with a big influence on climate is large and prolonged volcanic eruptions. These can introduce huge quantities of ash and gases into the atmosphere, altering global climate.

Mount Takahe's 192-year series of eruptions released a haze of fallout containing toxic heavy metals and hydrofluoric acid which extended for 2,800 km away or more. The fluorine-containing compounds interacted with the ozone layer in the atmosphere, degrading it and allowing more radiation from the sun to reach the Earth.

Residues detected in ice cores suggest that this event was large enough to trigger the melting of glaciers in the southern hemisphere.

"We postulate that these halogen-rich eruptions created a stratospheric ozone hole over Antarctica that, analogous to the modern ozone hole, led to large-scale changes in atmospheric circulation and hydroclimate throughout the southern hemisphere," said study author Joseph McConnell of the Desert Research Institute in a statement.

"Although the climate system already was primed for the switch, we argue that these changes initiated the shift from a largely glacial to a largely interglacial climate state. The probability that this was just a coincidence is negligible."

Massive eruptions with the potential to fundamentally alter the climate are still perfectly possible today, volcanologist John Smellie of the University of Leicester, who was not involved in the research, told IBTimes UK. Mount Tahake itself is potentially still active.

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"Mount Tahake was erupting 17 to 18,000 years ago. Geologically speaking, this is yesterday. If it erupted then, it's potentially perfectly capable of erupting again now."

But just one eruption wouldn't necessarily be fatal. Repeated eruptions over an extended period would most likely be necessary to have a huge and long-lasting environmental impact.

"The important feature of this event is that it was a series of at least nine eruptions taking place over nearly 200 years," Smellie said.

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