Written by Arshiya Sangar, a grade 11 student

The volcano Mount Sinabung in North Sumatra (an island in Indonesia) erupted on August 10, sending ash and other volcanic materials flying as high as 16,400 feet into the air. This was its second eruption since 8 August.

There were, however, no fatalities according to Indonesia’s Volcanology and Geological Hazard Mitigation Centre.

An Introduction to Mt Sinabung

It is one of more than 140 active volcanoes (those which have a history of eruption and are likely to erupt again) in Indonesia. It had been inactive for about 400 years before it erupted in 2010; it has been active ever since. Tens of thousands of people have had to leave their homes in areas around the volcano due to its eruptions.

The ‘Ring of Fire’ and its Relevance

Indonesia is located off the coast of mainland Southeast Asia in the Indian and Pacific oceans. The ‘Ring of Fire’ is a path along the Pacific Ocean, which is home to about 75% of the world’s volcanoes, and its tectonic activity (the shifting of plates in the Earth’s crust) results in about 90% of the world’s earthquakes. Mt Sinabung is a volcano on the Ring of Fire.

Types of Volcanoes

A majority of volcanoes form along the boundaries of tectonic plates, and can broadly be classified into five types :

Stratovolcanoes: The cone-shaped volcanoes we are most familiar with are stratovolcanoes. They contain thick and sticky lava (molten rock trapped underground which makes it to the surface), hence when pressure builds up, it leads to an explosive eruption. The building up of this lava on the sides of the volcano is also what leads to its conical shape. Mt Sinabung is a stratovolcano.

Shield Volcanoes: Shield volcanoes have runny lava, thus it spreads far away from the source forming a volcano with gentle slopes.

Fissure Vents: When magma (molten rock trapped underground) rises through a long fracture, it leads to ‘fountains of lava’ forming what looks like a ‘curtain of fire/lava’, which is called a fissure eruption.

Spatter Cones – When magma contains too much gas to form easy-flowing lava, but too little to form an explosion eruption (as seen in stratovolcanoes), it erupts as blobs which fall close to the vent forming a low, steep-sided cone, which is called a spatter cone.

Caldera Volcanoes – When a very large explosion eruption occurs, and the magma chamber (where magma is stored underground) is emptied, the roof of the chamber may collapse, forming a depression and thus a bowl-like surface with very steep walls. These are Calderas.

Experts suggest that more eruptions are likely in the coming days and weeks. Let’s keep our fingers crossed.