Giant volcanoes on Earth are waking up

A volcano appears to be moving near the Italian city of Naples, and this has nothing to do with the impending existence of Mount Vesuvius. Another volcano is lurking nearby, one that is very difficult to spot, but may be more dangerous than its cousin next door. It is becoming increasingly turbulent. Instead of forming a peak, Campi Flegri features a giant crater 13 kilometers (8 miles) wide, or caldera, formed after massive eruptions during prehistoric times. It is the closest thing we have to a giant volcano in Europe and is located directly under the coastal city of Pozzoli, just west of Naples.

Restless giants

The Campi Flegre volcano may erupt in the coming months or years, or it may return to its slumber. But it is just one of a number of restless volcanic giants across the planet, some of which pale in size and strength to Naples in terms of the size and power of previous eruptions. Among these giants, Yellowstone volcano is the most famous giant and rarely comes out of the news. The earth rises above and falls, and small earthquakes periodically shake the area. The volcano, which has been the focus of several television documentaries and at least one drama, takes center stage whenever there is debate about where the next giant eruption will tear apart the Earth's crust. Yellowstone has erupted three times in the last 2.1 million years, most recently 640,000 years ago, each time leaving the caldera to dwarf those beneath Pozzoli, the largest of which was more than 80 kilometers (50 miles) wide. Formed in a massive eruption 750,000 years ago, Caldera Long Valley in eastern California has also been turbulent since 1980, and has been recognized by the U.S. Geological Survey as a very significant threat. Yellowstone and Long Valley are two of about 20 volcanoes known to be the source of massive volcanic eruptions in the past. That is, explosive explosions that spew at least 1,000 cubic kilometers (240 cubic miles) of magma in the form of ash, rocks, and debris. Other volcanoes include Taupo in New Zealand and Toba in Sumatra. There's a lot we know about supervolcanoes, most notably that their largest eruption is capable of wiping out everything within a radius of at least 100 kilometers (62 miles), while the vast amounts of sulfur gases rising into the stratosphere can trigger bouts of dangerous global cooling, known as volcanic winters.

swollen with magma

It feels like giant volcanoes are beginning to reveal more of their secrets, and de Silva and his team have uncovered many of them using an approach he called "supervolcano forensics." The massive magma body beneath the giant volcano is able to remain largely molten because fresh magma is constantly introduced into it from below. The reason magma does not erupt in small bursts is that the enormous amount of heat generated by magma keeps the surrounding rocks flexible. This means that the crust above can swell to accommodate new magma, but it does not break (as if it were colder and brittle), so the paths do not open easily to the surface. However, eventually, once the magma body becomes so swollen that it is between 10,000–100,000 cubic kilometers (2,400–24,000 cubic miles) in volume, the crust above becomes unstable. Circular cracks develop on the surface and spread downward until they intersect the magma body, at which point all the lava is released. The central mass of the crust determined by the circular faults pushes down under the action of gravity, acting according to De Silva like a piston, pushing magma upwards through the cracks and pushing it outward at supersonic speeds, and with tremendous violentness, from multiple locations along the cracks. Eventually, the central mass of the crust stops falling, ending the eruption and leaving behind a volcano crater.

Is it time to start worrying?

Since everything about giant volcanoes is so huge, you might think that the massive eruption buildup could take much longer. However, research conducted in Long Valley suggests that the accumulation of its largest eruption, about 750,000 years ago, may have taken less than a year. From a disaster preparedness point of view, this is very bad news, not least because a massive explosion could have a tremendous impact on society and the global economy. The eruption of at least 2,800 cubic kilometers (671 cubic miles) of ash, debris and gas from the Toba volcano in Sumatra about 74,000 years ago led to several years of extreme cooling, which, if it happened today, would likely destroy crops worldwide. Having less than 12 months to prepare for such an event would make it extremely difficult to put in place the necessary measures for food storage and rationing, which would be required to minimize the impact. But realistically, do we need to worry about a massive volcanic eruption in the near future? After all, these eruptions are extremely rare. This is a long-term medium, so there can easily be clusters of massive volcanic eruptions in time, separated by much longer periods without any of them.