Volcanoes

A volcano forms when partially melted rock, or magma, rises above Earth’s crust from Earth’s interior. Volcanoes can be violent eruptions of smoke, ash, rock, and lava, or gentle lava flows. Volcanoes erupt when the pressure in a chamber causes the magma to rise and fracture the rock above it, providing a pathway for the magma to rise to Earth’s surface through a conduit to a vent. Magma can have different compositions. The composition determines the type of eruption and the classification of volcano. Shield volcanoes are wide and have a gentle slope formed from lava flows, cinder cone volcanoes are small and composed of pyroclastic material, and composite volcanoes are made of both pyroclastic material and lava flows. All three types of volcanoes are found in the Ring of Fire, and area surrounding the Pacific Ocean.