Why are some volcanoes more active than others?

Main topic: Science

Other topics: Volcanoes

Short answer:

• The composition of the magma (molten rock) and how easily gas can escape from it determine how explosive and active a volcano will be.
• Because they are viscous, high silica concentration magmas frequently erupt violently.
• Basaltic magma, on the other hand, is less silica-rich, more fluid, and does not spontaneously erupt in massive explosions.

Volcanoes are a very deadly and destructive force when they are actively erupting. However, while they are inactive, the soil they replenish can become highly productive, which encourages the development of communities and cities close by. Simply put, the frequency of a volcano's eruptions determines how it is classified. Active volcanoes are those that routinely erupt, while dormant volcanoes have previously erupted but are now silent (or inactive).

Mayon Volcano Eruption 4

Stratovolcanoes are the most active and violent due to high silica concentration magma

A Stratovolcano is a cone-shaped mountain formed by the accumulation of ash and lava. They are often the tallest volcano and are distinguished by their powerful eruptions. Volcanic ash comprises microscopic, sharp fragments of glassy snap-frozen lava and rock from the sides of the volcano vent. It is produced when gas bubbles build up in the magma, which has a high silica concentration and explodes.

Stratovolcano cross-section

Fuji in Japan, Etna in Italy, Agung in Bali, and Yasur in Vanuatu are a few examples of Stratovolcanoes.

Shield volcanoes are less active and not likely to build up and create explosions

Kilauea Shield Volcano Hawaii 20071209A

Magma from shield volcanoes has a comparatively low silica content.  They are less likely to build up and cause explosions since the magma is so hot and liquid, though they still have the potential to do so. In Hawaii and Iceland, shield volcanoes abound, notably Kilauea and Eyjafjallajökull. A shield volcano is the Manaro volcano on Vanuatu's Ambae Island.

Caldera volcanoes are also violent and formed when a volcano erupts and collapses

Mount Tambora volcano caldera, Sumbawa, Indonesia - July 28th, 2020 - Enhanced natural colors with IR overlay 3d rendering (50163795452)

The collapse of a volcano into the vacuum that is created when its magma chamber is empty results in the formation of a caldera. When a very huge and explosive eruption takes place, which empties the magma chamber, the ceiling of the magma chamber may collapse, forming a depression or bowl with extremely steep sides on the surface.  These are known as calderas, and their diameters may reach tens of kilometers. During a particularly strong eruption, a stratovolcano collapses into its magma chamber, causing Calderas to form.