The main parts of a volcano include the summit crater, the magma chamber, the central vent and the edifice. While volcanoes vary considerably in terms of size and shape, most land volcanoes have structural similarities.
Molten lava is released from the mouth of the volcano, known as the summit crater. The underground chamber in which the lava wells up is known as the magma chamber. The central vent joins the magma chamber and the summit crater. The edifice is the structure that surrounds the central vent. The varying shapes of the summit crater and the edifice characterize different types of volcanoes. The shape, structure and composition of the edifice are determined by the nature of the eruption and the volcanic material that erupts from the volcano, which builds the edifice.
Volcanoes have three basic shapes: stratovolcanoes, which have steep, symmetrical sides that lead up to a small summit crater; scoria cone volcanoes, which have a very wide summit crater with steep, symmetrical sides; and shield volcanoes, which are wide and short but become a bit steeper near their wide summit craters. Scoria cone volcanoes are the most common type of volcanoes.
Volcanic activity also creates other types of structures, such as calderas, which form when the magma chamber completely drains out, and lava domes, which form when the slow-pouring lava creates a dome that plugs the crater.