A volcano is a fissure in the crust of a planet or moon through which molten rock, hot gases, and other substances erupt. Volcanoes frequently develop a hill or mountain as a result of the accumulation of layers of rock and ash from numerous eruptions.
Volcanoes are categorized according to their state of activity: active, dormant, or extinct. Active volcanoes have recently erupted; they are quite likely to do so again. Dormant volcanoes have been dormant for an extended period of time but may erupt at some point in the future. Extinct volcanoes are unlikely to erupt again in the near future.
Within the magma chamber, pressure increases, causing the magma to flow through channels in the rock and out onto the planet's surface. When magma flows to the surface, it is referred to as lava.
Volcanoes can be found both on land and beneath the sea. When volcanoes erupt on the ocean floor, the ejected lava frequently forms underwater mountains and mountain ranges as it cools and hardens. When volcanoes on the ocean floor grow large enough to rise above the water's surface, they form islands.
Barring the basalt flows, the shield volcanoes are the largest of all the volcanoes on the earth. The most well-known examples are the Hawaiian volcanoes. These volcanoes are primarily composed of basalt, a kind of lava that erupts with great fluidity. As a result, these volcanoes are not particularly steep. They become explosive if water enters the vent; otherwise, they are non-explosive. The approaching lava flows in the form of a fountain and ejects the cone at the vent's top, eventually forming a cinder cone.
These volcanoes are distinguished by the emission of more viscous and cooler lavas than basalt. These volcanoes frequently erupt violently. Along with the lava, significant amounts of pyroclastic debris and ashfall to the ground. This debris collects near the vent entrances, resulting in the creation of strata, giving the mountains the appearance of composite volcanoes.
These are the most explosive volcanoes on the planet. They are typically so explosive that when they erupt, they collide with one another rather than erect any tall structures. Calderas are collapsed depressions. Their explosive nature indicates that the magma chamber that supplies the lava is not only massive but also nearby.
Flood Basalt Provinces
These volcanoes discharge very fluid lava across great distances. Some parts of the world are covered by thousands of sq. km of thick basalt lava flows. The Deccan Traps of India are a significantly larger flood basalt province that currently covers the majority of the Maharashtra plateau. It is believed that the trap formations originally covered a significantly bigger area than they do now.
Mid-Ocean Ridge Volcanoes
These volcanoes are found in oceanic regions. There is a network of around 70,000 km long mid-ocean ridges that runs through all of the ocean basins. The central portion of this ridge experiences frequent eruptions.
Volcanoes have existed on Earth for a long period, and are likely to have been responsible for calamities such as the Permian mass extinction approximately 250 million years ago, the largest mass extinction in Earth's history. Volcanoes can and have existed on other worlds as well: whereas volcanoes on the moon and Mars have been dormant for a long time, volcanoes on Jupiter's moon Io are still quite active.