There are a huge number of geological formations of various types on Earth. But the most interesting and dangerous of them are volcanoes. Some volcanoes are millions of years older than humanity, while others have appeared quite recently.
The term "Volcano" comes from the name of the fire god Vulcan. They designate geological formations in the crust of the Earth or another planet, through which volcanic gases and molten magma can come to the surface. This process is called a volcanic eruption.
Volcanic scientists are engaged in the study of volcanoes. They classify them by activity, location, and shape. The location of the volcanoes can be different. Today, both terrestrial and submarine and subglacial volcanoes are known.
The main characteristic of a volcano is its activity. Distinguish between extinct, dormant, dormant and active volcanoes (in order of increasing degree of activity). At the same time, eruptions are possible on all and from them, but on extinct ones, they are extremely unlikely. There is still debate among volcanologists about which volcanoes can be considered really active. Thus, active volcanoes are those that erupted during the observed historical period. However, it is known that after the last eruption, the volcano can remain active for millions of years.
Distinguish between linear and central volcanoes. The former exist in the form of extended faults in the planet's crust, the latter have a vent (central supply channel), on the one hand ending in a magma chamber, and on the other - in a crater. By the nature of their occurrence, volcanoes are distinguished monogenic and polygenic - appeared as a result of a single or multiple eruption, respectively.
According to their shape, volcanoes are divided into thyroid, cinder, dome and stratovolcanoes. Thyroids are flat due to the fact that their lava has a low density and often flows out of several foci at once. Slag volcanoes usually take the shape of a cone with gentle edges, as they emit mainly ash, stones and small debris. Dome volcanoes are characterized by the presence of a wide basalt "plug" (dome), as if covering the vent. Stratovolcanoes also have a conical structure, but it is heterogeneous, since the type of erupted substances alternates over time.