Question

What is a caldera? How are they formed?

Answer 1

Hint: Caldera is a large hollow structure that is formed after a magma chamber is emptied during a volcanic eruption. Till date only seven caldera forming collapses have been known to occur, the most recent one being at Iceland in 2014.

Complete answer:
Caldera are formed by means of a collapse which takes place due to the emptying of the magma chamber beneath a volcano that occurs due to large volcanic eruptions. When enough magma is ejected during volcanic eruption the emptied chamber cannot support the weight of the volcanic mass above it as a result of which a circular structure known as the ring fault develops.

With the emptying of the magma chamber the center of the volcano begins to collapse, finally leading to the formation of a caldera. The total area of a caldera is hundreds of square kilometers. There are two major types of caldera- explosive caldera eruptions and non-explosive caldera eruptions. Explosive caldera eruptions are known to be formed by magma which is rich in silica and thus has high viscosity. Non-explosive caldera in turn is made up of magma which is rich in basalt and poor in silica and thus is less viscous.

Note: Caldera are important as they consist of rich ore deposits. The ores comprises different metals ranging from gold, silver, lead, mercury and lithium. Sturgeon Lake Caldera located in northwestern Ontario, Canada is known to be one of the world’s best preserved mineralized caldera.