Why do volcanoes erupt?

Ground Report | New Delhi: Why do volcanoes erupt; More than 25,000 earthquakes served as a prelude to the eighth volcanic eruption that occurs on La Palma, which at the moment continues to expel fiery lava through the hills of the Cumbre Vieja Natural Park. Precisely, that region is the one with the highest concentration of volcanic craters (or volcanoes) on the island and where the Teneguía volcano rests, the now penultimate to star in an eruption in Spain.

Despite the differences between all these volcanoes, they all have one point in common: they are a manifestation on the earth's surface of a long geological process by which the energy locked inside our planet is released, according to the National Geographic Institute ( IGN). In this sense, and although there are other factors, what makes each volcano rather unique is the way it releases all that energy that creates pressures inside the planet.

Why do volcanoes erupt?

In the case of the recent La Palma volcano, experts point out that it is a Strombolian volcano, that is, one in which small explosions are generated due to the accumulation of gases inside the volcano and that, due to the thickness from magma, they find it difficult to get out onto the mainland.

It could be said that it is the complete opposite of the Hawaiian eruption, where the lava that comes out is liquid and travels rapidly across the surface forming volcanic buildings (reliefs created by the solidification of lava) long instead of tall, as occurs in Tenerife with the most emblematic volcano in Spain: Teide.

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In any case, according to a group of geologists, the viscosity of the molten rock that makes its way into it will depend on the volcanic crystals that form in the channels of the volcano and that "modify the chemical composition of magma (called lava when it goes outside after the explosion) ”.

For experts, these crystals have the ability to function as a filter that sequesters magma elements that reduce the density of the molten rock and increase its gas content. When a high gas content is reached, the pressure ends up pushing the magma towards the eruptive mouth, where the material finally comes out. (Why do volcanoes erupt)

As a curiosity, there are volcanoes in which the magma reaches such a density that, during its exit through the eruptive mouth, a plug is formed that makes it impossible for the magma and gases to escape. In these cases, the enormous pressure generated inside the volcano causes the volcanic cone where the mouth is located to explode with enormous violence, throwing pyroclasts (a solid fragment of volcanic material) and fiery clouds of lava and gases.

Origin of the volcanoes

Volcanoes mainly originate at divergent boundaries between two tectonic plates, although they do not exclude converging regions either. In the first case, the separation between plates reveals an area of ​​the interior of the Earth where magma emerges, which rises to the surface due to the force of the pressures and the convection currents that operate in the mantle.

In the second case, the plate that enters the interior of the mantle little by little melts into magma that will filter through different cracks in the rocks to the surface, where it will cause a volcanic eruption.

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The case of the Canary Islands is stranger if possible. According to the IGN, its prolonged activity does not agree with the volcano-tectonic attributes that would correspond to its location on a passive continental margin, but rather it is, in general terms, a volcanic zone of hot spots.

In this case, isolated plumes of magma come out and remain active for millions of years. Since the feathers remain fixed, but the crust does not, it allows the magma to form chains of islands as tectonic movements occur. However, the birth of the Canary archipelago is still a mystery and others point to other theories.

In any case, for the IGN, the Canary Islands constitute one of the most interesting active volcanic regions on the planet: “Its study is linked to the first steps of current volcanology, reflected in the works of great naturalists of the 19th century, such as Humboldt or von Buch, which have been completed and improved throughout the 20th and 21st centuries with the help of new technologies ”, he points out.

The dangers of volcanoes

Regardless of the type of volcanic eruption we face or how it is formed, nearby populations typically face seven major dangers that, if not treated with caution, can trigger major tragedies. For example, Krakatoa, one of the most dangerous volcanoes in the world, is famous for its explosions that could be heard up to 5,000 kilometers away and whose consequences took the lives of 36,000 people.

One of the first dangers referred to by the IGN is the lava flows, that is, the path that the lava follows from the eruptive mouth through the volcanic building. As detailed, the path that follows depends on the topography, the physical properties of the lava, and the rate of emission. (Why do volcanoes erupt)

"In general, very fluid lavas tend to occupy large areas with little thickness, while more viscous lavas are higher and travel shorter distances," they clarify. The flow of pyroclasts is another of the great threats since, in cases where there are explosions, it can create dense flows of a mixture of gases and solid particles at a very high temperature that travel up to 550 kilometers per hour, called pyroclastic flows.

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