Nothing seems out of the ordinary when looking over the 100 km long and 30 km wide Lake Toba on the Indonesian island of Sumatra. Under the mirror-smooth surface of the lake, however, there are supervolcanoes that caused the cooling of the entire planet almost 75,000 years ago.
In a period of only two to three weeks, about 2,800 cubic kilometers of volcanic material were blown into the air, which corresponds to the mass of two Everest mountains.
The amount of ash alone would have been enough to cover all of Iceland with an ash layer 10 meters thick.
Fortunately, such eruptions are extremely rare, but scientists estimate that supervolcanoes erupt only every 100,000 years.
We may soon have to prepare for new disasters caused by these doomsday volcanoes, but the latest research indicates that the world’s most dangerous supervolcanoes are starting to slow down.
An eruption would darken the entire world
Supervolcanoes differ from conventional volcanoes in that they are connected to huge volcanic craters far down in the earth. As a result, eruptions from supervolcanoes often become so powerful that they blow themselves up, often leaving only craters with water in them.
Such supervolcanoes can be found all over the world, but a total of 27 supervolcanoes are known on the planet.
The largest supervolcanoes are deep underground beneath Yellowstone National Park in the United States. It last erupted 640,000 years ago.
Ash clouds and sulfuric acid cause death and destruction
The most dangerous weapons of supervolcanoes are ash and sulfur that can darken the sky and block out the sun’s rays. Volcanic eruptions can cause a sudden drop in the Earth’s temperature every few years.
Volcanoes are classified according to their explosiveness on the so-called VEI scale (Eng.: Volcano Explosivity Index). The scale ranges from zero to eight, and volcanoes that erupt on a scale of seven to eight are classified as supervolcanoes.
Scientists analyze what triggers eruptions from supervolcanoes, but various theories support that eruptions occur when the pressure in the air over underground volcanoes decreases and ground shaking subsides, so that the magma has as a result made its way up.
Why are supervolcanoes dangerous?
When a supervolcano erupts, it pumps at least 1,000 cubic kilometers of magma from the bowels of the earth and up to 25 km high plumes of ash are shot into the air.
These air layers contain the stratosphere, from which ash particles, as well as the toxic gas sulfur dioxide, can spread.
Since there is not a lot of precipitation from such high air layers, the ejecta can float around for a long time and spread around the globe by wind gusts. This can be effective for the climate.
Air suspension of sulfur dioxide, i.e. tiny sulfuric acid droplets, can remain in the atmosphere for years and since they reflect sunlight, the sunlight does not reach the earth. The result is manifested in a massive drop in temperature.
Eruptions from supervolcanoes have a particularly strong effect on the climate when they occur in tropical regions.
It is not enough that the effervescent material can reflect a large amount of sunlight, but the material also spreads easily to both the northern and southern hemispheres, and the combined effect manifests itself in increased cooling.
The last supervolcano eruptions
26,500 years ago : The Taupo volcano on the North Island of New Zealand
76,000 years ago : Lake Toba, Sumatra, Indonesia
340,000 years ago : Taupo volcano, on the North Island of New Zealand
Disaster possible in Italy
The Campi Flegrei super volcanoes are hidden far below the city of Naples. The volcanoes last erupted in 1538, and the eruption was so small that it did not cause global temperature changes.
Campi Flegrei means “burning fields” in ancient Greek, and if Italian scientists are anything to go by, there is a risk that everything in Italy, and indeed many parts of the world before long, could go up in flames due to these dormant volcanoes.
Campi Flegrei is a supervolcano that covers approx. 13 km large area with about 24 craters. One of the craters is Solfatara di Pozzuoli, which often spews steam and sulfurous gases.
Ever since the mid-20th century, the volcano has shown signs of awakening from hibernation, and in 2005 scientists at the Institute of Geology at the University of Bologna in Italy measured increased pressure in the supervolcano’s magma.
If the pressure increases significantly, there is a risk that the lid over the underground furnaces will pop open like a cork and unleash a powerful eruption that will have consequences all over the world.
“We want to draw attention to the fact that the magma in Campi Flegrei may have reached the point where the gas pressure is at a dangerous level. This process may lead to an eruption”, wrote one of the leading volcanologists, Giovanni Chiodini, in an article published in the prestigious journal Nature in 2016.
Scientists analyze when a possible eruption may begin. It could happen in a few decades or in hundreds of years.
One thing is certain, however, and that is that it is wise to keep a close eye on the supervolcano so that not only Italy, but also the entire world, can prepare for a possible volcanic winter.
