Volcano

A volcano is an opening in the earth from which molten rock and gas erupts. The molten rock (magma) forms a hill or mountain around the opening and the burning gas, ash, and hot lava may explode out or pour down the sides. The explosion of a volcano is called an eruption and can do much damage, as seen in Pompeii and Washington state's Mount St. Helens. There are about 800 places in the world where volcanoes are active, including 80 below the sea. There are belts were there are volcanoes, including one large one circling the Pacific Odean and others running east-west in Indonesia and the Mediterranean Sea. The materials deep underground move around and push up to the mouth of the volcano. The theory of plate tectonics says that huge plates of material making up the Earth's crust shift and volcanoes erupt where the plates meet and push together. Some can be dormant for years and then suddenly erupt. Others become extinct. Mauna Loa in Hawaii is the world's largest volcano. Th e study of volcanoes is called volcanology."