The document discusses volcanoes. It explains that volcanoes are formed by tectonic plates pushing magma, or molten rock, up from under the earth's surface. When the magma reaches the surface, it erupts out of the volcano's crater as lava, ash, and gases. The lava hardens into volcanic rock after it cools. The document also notes that volcanologists study volcanoes and that there is a volcanic zone near Olot, Catalonia where people can visit volcanoes and a volcanoes museum.