: Many hills have craters at the top . Burning stones and metals come out of that hole in the throat state. For example, smoke comes out of a brick kiln chimney. These are called volcanoes as ash , smoke , rock , metal, etc. are emitted from the top of these hills. The reason for the formation of volcanoes is the hard crust on the surface of the earth is called crust. And beneath it there is deadly heat and fluid. She is called Magma. If a crack is found on the crust , or if a raw spot is found, it cracks and comes out on the magma. The molten fire penetrates the ground and rises to the surface and freezes in the form of stubs or mountains. We call these types of mounds or mountains the cause of volcanoes.