The formation of volcanoes is due to the condensation and accumulation of magma or clastic materials ejected from the crust by the rock movement. The typical shape of a volcano is a cone-shaped hill, called a volcanic cone. There is usually a crater at the top of the cone, which is a concave depression with a small area. It is determined by the last eruption and has no direct relationship with the volume of the volcano.
After the volcanic activity stops, the volcanic channel under the crater is easy to solidify into lava column, which is called volcanic neck. The volcanic neck is connected with the molten magma deep in the crust. In general, the nature of the lava determines the intensity of the eruption and the appearance of the volcano. When the lava is acidic lava, the volcanic eruption intensity is high and the volcanic slope is large; When the lava is alkaline, the eruption intensity is small, and the appearance of the volcano is usually shield shaped. According to volcanic activity, volcanoes can be divided into active volcano, dead volcano and dormant volcano.