The three most worrying supervolcanoes in the world



by LORENZO CIOTTI

The three most worrying supervolcanoes in the world

A supervolcano is a caldera on the Earth's surface, with a diameter of several tens of kilometers. These structures are identified at ground level and cannot be associated with the collapse of previous volcanic buildings such as normal calderas.

These structures are not considered true volcanoes, as there is no visible volcanic edifice. Inside the large calderas it is possible to notice the development of various more or less formed craters and the presence of secondary volcanism.

An eruption of this type of caldera has never been observed, although clear geological traces of massive past eruptions are found in the surrounding areas. The best-known examples of this type of system are Yellowstone Park (USA), Campi Flegrei (Italy), Lake Toba (Indonesia).

The Yellowstone Caldera is the supervolcano caldera located beneath Yellowstone National Park, in the United States of America. The caldera is located in northwest Wyoming, where most of the park area is located. The dimensions of the area considered volcanic are very large: 55 by 72 kilometers in extension.

The caldera is also better known as the Yellowstone supervolcano, after a BBC documentary gave it this name. Over the course of 17 million years, the caldera generated a succession of violent eruptions and rhyolitic lava flows that would give life to the eastern part of the Snake River Plain.

At least a dozen of these eruptions were so violent that they were considered supereruptions. In reality the supervolcano is not made up of a single caldera, but of several calderas close to each other. The oldest of these is McDermitt, between Nevada and Oregon.

Some more recently formed calderas are progressively extending, including parts of Nevada, Oregon and the eastern area of the Snake River Plain, ending in the Yellowstone Plateau.

The Campi Flegrei are a vast area located in the gulf of Pozzuoli, west of the city of Naples and its gulf.

The area has been known since ancient times for its lively volcanic activity. It is an ancient supervolcano.

From 1970 to 1972 bradyseism caused an episode of ground lifting of around 170 centimeters in the port of Pozzuoli, and from 1982 to 1984 there was a second ground rising which brought the quays to rise to a height of around 3 metres; a downward phase occurred from the end of 1984, which ended in 2005; since then there has been a progressive increase again.

It should be noted that in the two-year period 1982-1984 approximately 10,000 earthquakes were detected, a few hundred also felt by the population. The Campi Flegrei constitute an area at high volcanic risk subjected to constant surveillance by the Vesuvian Observatory, both through periodic investigation campaigns and with continuous monitoring.

Lake Toba is a 100 km long and 30 km wide volcanic lake located in the northern part of the island of Sumatra in Indonesia and a vestige of a theorized natural disaster. The eruption of the supervolcano is traced back to 70-78 000 years ago.

It is considered one of the most catastrophic of the last 500,000 years. In the Volcanic Explosivity Index scale it is classified with a magnitude of 8. According to researchers Bill Rose and Craig Chesner of Michigan Technological University, the volume of the erupted material was approximately 2800 km³, of which approximately 2000 km³ of ignimbrite and 800 km³ of ashes that buried the entire region under numerous meters of deposits.

It is estimated that in the region around the volcano they reached a height of over 400 meters and sediments of over 4 m are present in many Indian regions. The eruption took place over several weeks and eventually the entire region collapsed leaving a large crater that filled with water and in the center a new mountain which today reaches 1600 meters above sea level and which forms the island of Samosir.

Surely such an event left tremendous wounds throughout the global ecosystem of the time. Many organisms were pushed to the brink of extinction and from studies on the human mitochondrion some research suggests that around 75,000 years ago the human species was reduced to a few thousand individuals.

This bottleneck in the size of the human population partly explains the low genetic variability in our species. Some researchers trace the cause of that drastic reduction to the Toba eruption. This theory for now does not appear to be in contradiction with the matrilineal dating of mitochondrial Eve and the patrilineal dating of Y-chromosomal Adam.