SUPERVOLCANO eruptions are virtually impossible to predict and that could have devastating consequences for the globe. Scientists have, therefore, called today for more research and monitoring of these volcanic systems to better understand their warning signs of an impending eruption.

Supervolcano eruptions rock the planet once every 100,000 years on average and though rare, their impacts are far-reaching. When the Toba supervolcano in Indonesia erupted some 74,000 years ago, there is some evidence to suggest it spewed enough ash into the skies to trigger an ice age – a cataclysm humanity only barely managed to survive. It is, therefore, rather worrying to learn there is no universally agreed-upon set of warning signs that precede a supereruption.

Estimates vary but there are about 12 supervolcanoes peppered around the planet – including the world-famous Yellowstone volcano in the western United States.

Writing today (July 27) in Nature Reviews Earth and Environment, a team of scientists has warned trying to predict when any of these volcanoes might erupt is extremely challenging.

The alert follows an in-depth review of 13 supervolcano eruptions over the last two million years, including the relatively recent Oruanui eruption in New Zealand 25,400 years ago.

The scientists found there is no single model for how these eruptions begin and unfold – and that makes predicting future eruptions a problem.

According to the US Geological Survey (USGS), supervolcanoes are volcanoes that have had one or more eruption of magnitude 8 on the Volcanic Eruption Index (VEI).

Eruptions of magnitude 8 and above release more than 1,000 cubic kilometres of material, which is enough to possibly disrupt the climate for decades to come.

During Yellowstone’s three big eruptions between 2.1 million and 640,000 years ago, the volcano released enough ash to cover much of the western half of North America.

It is a good thing then Yellowstone is not about to erupt anytime soon – but what about the other supervolcanoes?

The team of scientists, which includes experts from Cardiff University, found the youngest Toba eruption 74,000 years ago, for instance, was a very abrupt eruption marked by the immediate collapse of the volcano’s chamber roof.

In stark contrast, the Oruanui eruption of New Zealand’s Taupo Volcano was a much slower affair.

The volcano deposited a large blanket of ash before its caldera collapsed and progressed intermittently with a number of pauses over a period of several months.

The amount of magma spewed by the volcanoes also varied from eruption to eruption.

The scientists consequently believe we need to spend more time monitoring these systems to better understand how they behave now and in the future.

Yellowstone, for example, is very seismically active but geologists are confident this is not an indicator of a brewing eruption.

But could the same be said of the Taupo volcano in New Zealand or the Phlegraean Fields in Italy?

According to study co-author Dr George Cooper, from Cardiff University’s School of Earth and Environmental Sciences, geologists need to understand what is “normal” for these volcanoes so that we are better prepared when they start to exhibit unusual signs of activity.

He told “Another supervolcanic system where we see these non-eruptive unrest episodes is Taupo Volcano, New Zealand.

“Recent work using the locations and patterns of earthquakes and ground deformation has allowed scientists to infer the current location of the magma reservoir containing molten rock.