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Could a huge, prolonged volcanic eruption, like those said to have caused several past mass extinctions, happen again?

Mike Follows
Sutton Coldfield, West Midlands, UK

Yes, huge, prolonged volcanic eruptions could happen again, though there are usually warning signs. Increased seismic activity, changes in gas emissions and ground swelling often precede an eruption. These can be monitored, as can changes in thermal images taken of volcanoes.

Despite these advances, the exact timing, magnitude and nature of an eruption are difficult to predict. However, effective monitoring led to the correct prediction of the 1980 eruption of Mount St Helens in the US and the 1991 eruption of Mount Pinatubo in the Philippines, though it was bigger than expected.

Basalt flows produced by several volcanoes created the Deccan Traps in western India during the Late Cretaceous Period, around 66 million years ago, and are associated with the mass extinction that included the demise of most of the dinosaurs.

Scientists predict a section of the Cumbre Vieja volcano will drop into the ocean, sending a tsunami across the Atlantic

The Yellowstone supervolcano in the US is expected to erupt in the future and have a similar impact to the 1991 Mount Pinatubo eruption, which temporarily reduced global temperatures by 0.5掳C. Some scientists have that a large section of the Cumbre Vieja volcano on La Palma will collapse into the ocean if it erupts, sending a tsunami racing across the Atlantic to devastate the eastern seaboard of the US, which could have significant economic and political repercussions.

It is possible that, in future, volcanoes could be 鈥渄efused鈥� by cooling the magma or reducing the pressure in the system.

Earthquakes, which often accompany and can even trigger eruptions, are also tricky to predict. The manslaughter convictions of six scientists (later overturned) and a government official for failing to predict the 2009 L鈥橝quila earthquake in Italy caused uproar in the scientific community.

Advances in technology, such as seismometers and GPS, have improved our ability to monitor seismic activity and understand tectonic movements, which helps scientists to assess earthquake risks. Scientists can make long-term probabilistic forecasts based on the study of fault lines, historical seismic activity and geological conditions. While some patterns and precursors, like small fore-shocks or changes in groundwater levels, can occur, they aren鈥檛 consistent enough to serve as reliable indicators of an imminent earthquake.

Hillary Shaw
Newport, Shropshire, UK

In short, yes. There are several supervolcanoes around the world that may erupt in the future. Yellowstone is perhaps the best known, but there are others in South America, the Mediterranean, Indonesia and the western Pacific rim.

Lakes in show land tilting, with submerged trees at one end and dry lake bed at the other, indicating the lava body below may be growing.

Two examples from history come to mind that showcase the devastating effects of large eruptions. Firstly, there was the Laki eruption in Iceland beginning in 1783, which caused mass casualties and also cooled the global climate. Secondly, there was the global volcanic winter of AD 536, when Procopius in Constantinople recorded the appearance of a strange, dark cloud that stayed put for months, perhaps originating from massive eruptions partway around the globe in North America, causing global cooling and crop failures.

Similar effects to these could also be produced without a massive volcanic eruption, for example if a large asteroid hit Earth. There would be a global drop in temperature, there might also be acid rain from the sulphur ejected, as well as crop failures, starvation and extinctions. And the species that produced this magazine may well be among those that go extinct.

To answer this question 鈥� or ask a new one 鈥� email lastword@newscientist.com.

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