A volcano is a natural phenomenon which can be described as a rupture or an opening in the crust of the surface of the earth from which hot magma and many types of gases escape. This phenomenon generally takes places at a place where the tectonic plates are either converging or are diverging away from each other.
An example of a volcano which occurs due to diverging tectonic plates is Mid Atlantic ridge. Pacific ring of fire is the example of a volcano where tectonic plates are found to be converging.
Volcanoes can vary from each other in magnitude and after effects. The biggest volcano in the world is the Mount Etna volcano which is in Italy and serves an area of 459 square miles.
Another volcano which is among the biggest volcanoes out there is Antillanca group which spreads over an area of 380 square miles. Mount Tambora is another volcano spreading over a large area of 312 square miles, making it one of the biggest volcanoes in the entire world.
Some other biggest volcanoes in the world in terms of the area that they spread over are Nevado Del Ruiz volcano in Colombia, Mount Shishaldin volcano in Alaska and Mauna Loa volcano in Hawaii , US.