Answer: A volcano is a rupture in the crust of the Earth where gases, ashes, and molten lava escape from a magma chamber below the crust. The process of eruption of volcanoes is called Volcanism. Global distribution of volcanoes: Volcanoes are located in a fairly defined pattern around the world, mostly associated with the weaker zones of the earth’s crust and generally overlap with zones of seismic activities like earthquakes. They also occur along coastal mountain ranges, as off-shore islands, and in the midst of the oceans, but there are few in the interiors of continents. The main volcanic belts are as under: Circum-Pacific Belt: It includes the volcanoes of the eastern and western coastal areas of the Pacific Ocean. This belt is also known as the Ring of Fire of the Pacific Ocean. Most of the high volcanic cones and volcanic mountains are found in the Circum-Pacific Belt. Examples include Cotopaxi in the Andes (the highest volcanic mountain in the world), Fujiyama (Japan) Shasta, Rainier, and Mt. St Helena (USA). Mid-Continental Belt: These are volcanoes of the Alpine mountains and the Mediterranean Sea. The volcanic eruptions are caused due to the convergence and collision of the Eurasian plate and the African and Indian plates. Examples include Stromboli, Vesuvius, Etna, etc. Mid-Atlantic Belt: It includes the volcanoes along the mid-Atlantic ridge which is the divergent plate zone. They are mainly of the fissure eruption type. Iceland is the most active volcanic area. As per the US Geological Survey, there are around 1,350 potentially active volcanoes worldwide and 75% of them are found along the Circum-Pacific Belt or the Ring of Fire. Also, about 90 percent of the world’s earthquakes occur here. The abundance of volcanoes along the Ring of Fire is caused by:

• Presence of a large number of tectonic plates: The area is along several tectonic plates including the Pacific plate, Philippine plate, Juan de Fuca plate, Cocos plate, Nazca plate, and North American plate. The movement of these plates or tectonic activity leads to abundant earthquakes and tsunamis every year.
• The amount of movement of tectonic plates in the area: Along much of the Ring of Fire, plates overlap at convergent boundaries called subduction zones. That is, the plate that is underneath, is pushed down, or subducted, by the plate above. As rock is subducted, it melts and becomes magma. The abundance of magma this close to Earth’s surface gives rise to conditions ripe for volcanic activity. For example, in the case of Tonga (January 2022 eruption), the Pacific plate was pushed down below the Indo-Australian plate and Tonga plate, causing the molten rock to rise above and form a chain of volcanoes.

The entire Pacific Ring of Fire has active volcanoes except at some gaps in the Ring such as at the San Andreas Transform plate boundary, where the Pacific plate and the North American plate move sideways. This type of boundary generates a large number of shallow earthquakes as tension in the Earth’s crust builds up and is released, but sufficient magma is not formed to create volcanic eruptions.