How does a volcano erupt?

Deep within the Earth it is so hot that some rocks slowly melt and become a thick flowing substance called magma. Because it is lighter than the solid rock around it, magma rises and collects in magma chambers. Eventually, some of the magma pushes through vents and fissures in the Earth's surface. read more

Volcanic eruptions can either be effusive or explosive. An effusive volcanic eruption occurs when the lava pours out onto the ground from the volcano's vent. When the molten rock or magma is thin and runny, gases can easily escape and the lava flows freely and travels far. read more

Ash erupted into the sky falls back to Earth like powdery snow. If thick enough, blankets of ash can suffocate plants, animals, and humans. When hot volcanic materials mix with water from streams or melted snow and ice, mudflows form. Mudflows have buried entire communities located near erupting volcanoes. read more

Volcanoes come in many shapes and sizes, ranging from common cinder cone volcanoes that build up from repeated eruptions and lava domes that pile up over volcanic vents to broad shield volcanoes and composite volcanoes. Though they differ in terms of structure and appearance, they all share two things. read more

With each eruption, rocks, lava and ash build up around the volcanic vent. The nature of the eruption depends on the viscosity of the magma. When the lava flows easily, it can travel far and create wide shield volcanoes. read more