What are Volcanoes?

Outline:

• Definition of volcanoes

• Formation of volcanoes:• Stages of volcanoes• Steps of formation

Definition of Volcanoes

Volcano is a mountain that opens downward to a pool of molten rock below the surface of the earth. When pressure builds up, eruptions occur. Gases and rock shoot up through the opening and spill over or fill the air with lava fragments. mudflows and rockfalls.

Formation of Volcanoes

Stages of volcanoes:

Scientists have categorized volcanoes into three main categories: active, dormant and extinct.

• Active volcano: is one which has recently erupted and there is a possibility that it may erupt soon.

• Dormant volcano: is one which has not erupted in a long time but there is a possibility it can erupt in the future.

• Extinct volcano: is one which has erupted thousands of years ago and there’s no possibility of eruption.

Steps of formation:

Volcano is formed when magma, present in the Earth's interior, manages to rise up to the surface via a vent or a fissure. Hot ash and gases also escape from the interior of the Earth, along with magma. While the gases get thrown into the air, the magma and ash cool down forming distinctive volcanic landforms.

To understand in detail, the process of formation of volcanoes, one has to understand what lies beneath the surface of the Earth.

• The Earth is essentially made up of five different layers viz., the solid inner core, the liquid outer core, the liquid inner mantle, the upper mantle, and the crust.

• The upper mantle comprises two distinct layers. The lower layer is the asthenosphere, which is semi-fluid in form, and the upper layer is that of the uppermost mantle, a.k.a rigid mantle, which is a solid layer of rock, just below the Earth's crust.

• The Earth's crust and the uppermost solid mantle together form the lithosphere.

• The Earth's lithosphere is like a huge jigsaw puzzle, with pieces of different shapes and sizes fitting into each other perfectly. These pieces are known as tectonic plates.

• The lithosphere (and hence the tectonic plates) rests on the asthenosphere (the lower layer of the upper mantle), which is the center of most volcanic activity that takesplace underneath the Earth.The asthenosphere is highly vicious and ductile.

• Since the asthenosphere is semi-fluid, it is obviously not stationery. Hence, the tectonic plates that rest on it are always in motion. However, this motion is too slow to be perceived by human senses.

• The tectonic plates display three kinds of movements. They either move towards each other (convergent boundaries) or away from each other (divergent boundaries) or just slide past each other (transform boundaries) in a horizontal manner.