Catastrophe of a Super Eruption

Image description: The Greek island of Santorini is a volcanic island reshaped between 1650 and 1598 BC by a terrifying explosion that swallowed the center of the island and dislocated Santorini into several islets around the caldera. Satellite image of the Santorini archipelago, with the island of Santorini on the right and an incomplete ring of 8 km in diameter and 85 km², in the center the islands of Thera and Therasia, which are the remnants of the ancient island of Kallistē before the volcanic collapse of the caldera.

Super Eruption of the Island of Santorini

Super eruptions are a thousand times more powerful than the largest volcanic eruptions witnessed by humanity in recent decades. The consequences of a super eruption are unimaginably catastrophic. They can cause considerable damage on a continental scale and have cataclysmic effects on life on Earth.

One of the most enigmatic is that of the Island of Santorini, which some volcanologists believe was the cause of the disappearance of the Minoan civilization in the Aegean Sea 3,600 years ago. It is likely that the legend of Atlantis, told by Plato in the 4th century BC, stems from this Aegean catastrophe.

The islands of the Cyclades in the Aegean Sea are located along a microplate at the boundary between the African plate and the European plate. The pressure of these large plates on the Aegean arc has given rise to these islands through the accumulation of flows and projections, first submarine and then aerial.

The Super Catastrophe

The first phase of the catastrophe is characterized by numerous small earthquakes that will last for days and days with strong shocks at times. Then the ashes and gases escape from the volcanic vent, the ground cracks and is covered with several decimeters of ash. This is the eruption heralding the super catastrophe.

The next phase is explosive, the so-called Plinian eruption characterized by a mushroom-shaped column sends millions of tons of pumice into the skies. The pumice propelled like revolver bullets falls, piles up, and accumulates at lightning speed, the layer increases by about 20 cm every hour on the surface of the island and around the island for hundreds of kilometers. Then the pumice is replaced by ash, tiny particles of ash that rise into the stratosphere up to 50 km in altitude.

A new phase of the eruption will start, the so-called phreatomagmatic phase, which is characterized by violent explosions of steam and ash, caused by the interaction of magma and water. The seawater that pours into the vent comes into contact with the molten magma, the water and the magma do not mix, they explode. The explosion produces a series of silent pyroclastic flows that rush one after the other at crazy speeds over the ashy landscape. Composed of rocks and gas, the pyroclastic flows reach temperatures of 700 °C and speeds of 290 km/h.

The Collapse of the Caldera

The upper part of the volcano collapses and falls into the magma chamber, this is the collapse of the caldera. Enormous rocks the size of a car burst out like missiles. The power is enormous, equivalent to tens of thousands of times the Hiroshima bomb.

In the immense plume that covers the volcano, lightning strikes illuminate the entire sky. The magma chamber partially empties, the volcano ejects tens of billions of tons of magma that will bury the lands for a long time under a hundred meters of ash, blocks, and pumice.

The pumice that floats on the water covers part of the sea with a layer so thick (1 meter) that you can walk on it. Large islands of pumice drift, carried by the waves, even by boat, one cannot escape this hell and the worst is yet to come.

The several hundred-degree pyroclastic flows that run above the waves, associated with the collapse of the magma chamber, will generate a gigantic tsunami several tens of meters high. The devastation of the surrounding islands is underway.

Then the billions of tons of ash projected into the sky will rise into the upper atmosphere and, carried by the wind, will travel around the Earth. The tiny particles of ash agglomerated in the clouds will cause torrential rains. This dark cover in the sky will modify the climate and lower the average temperature of the planet by several degrees for dozens of years.

Consequences of the Collapse

After a few weeks, the general cooling is about 10°C, the snow will cover the lands up to the mid-latitudes for several years. Humanity then enters a little ice age with all the consequences one can imagine. The fine ashes will infiltrate everywhere, pollute the waters, cover the crops, disrupt the monsoons, and cause famine among the 30 to 50 million people on Earth.

N.B.: Pumice or pumice stones are very porous volcanic rocks with a low density, frequently less than 1, which allows them to float on the surface of the water.

The Supervolcanoes That Threaten Us

Supervolcanoes are volcanoes capable of producing extremely massive eruptions, with volumes of ejected material greater than 1,000 km³. These eruptions can have catastrophic impacts on the global climate and ecosystems. Which are the most well-known and potentially threatening supervolcanoes?

• Yellowstone Caldera (United States): The last major eruption occurred about 640,000 years ago. Although the probability of a major eruption is low in the short term, such an eruption would have devastating consequences for the United States and the world.
• Lake Toba (Indonesia): The last major eruption occurred about 75,000 years ago. Lake Toba is the site of one of the largest known volcanic eruptions. Although it is currently dormant, a future eruption could have global impacts.
• Long Valley Caldera (United States): The last major eruption occurred about 760,000 years ago. This caldera is active and shows signs of ground deformation and seismic activity, indicating possible magma accumulation.
• Taupo Caldera (New Zealand): The last major eruption occurred about 26,500 years ago (Oruanui eruption). Lake Taupo is the site of one of the largest volcanic eruptions of the last 70,000 years. A future eruption could have significant impacts on New Zealand and beyond.
• Valles Caldera (United States): The last major eruption occurred about 1.25 million years ago. Although less well-known than Yellowstone, the Valles Caldera also presents a potential risk of a major eruption.
• Campi Flegrei Caldera (Italy): The last major eruption occurred about 39,000 years ago (Campanian Ignimbrite eruption). This caldera is active and shows signs of ground deformation, indicating possible magma accumulation.

Volcanic Eruption Classification Index

The Volcanic Explosivity Index, or VEI scale (Volcanic Explosivity Index), was invented in 1982 by Chris Newhall of the United States Geological Survey and Steve Self of the University of Hawaii.