What is a volcano?

A volcano is a mountain or hill, conical in shape and has a vent or hole called crater through which lava or magma, gases, rocks, and fragments come out. In other words, it is a rupture in the crust of the earth and not only of the earth but also on other celestial bodies. When the material escapes, it causes an eruption. An eruption can be explosive, sending material high into the sky or it can be calmer with gentle flows of the material.