Volcan

Volcan, commonly referred to as volcano in English, is a rupture in a planet's crust that allows molten rock, volcanic ash, and gases to escape from a magma chamber. On Earth, most volcanoes form at tectonic plate boundaries or over mantle plumes known as hotspots. The emitted material can be lava that flows as streams, volcanic ash that can travel thousands of kilometers, and gases such as water vapor, carbon dioxide, and sulfur dioxide. The basic structure includes a vent or vents, a magma chamber, and often a crater, cone, or caldera formed by eruption and collapse.

Volcanoes are classified by eruption style and shape. Shield volcanoes have broad, gently sloping sides and usually erupt low-viscosity basaltic lava, producing lava flows. Strato/composite volcanoes have steep profiles and alternate explosive bursts with lava flows, often built from andesitic to rhyolitic lavas. Cinder cones are small, steep cones built from tephra. Lava domes form from highly viscous magma that piles up near the vent. There are also submarine volcanoes and fissure eruptions along cracks in the crust.

Eruptions range from effusive lava flows to catastrophic explosive events that eject ash clouds, pumice, and pyroclastic flows. Hazards include lava flows, ash fall that disrupts aviation and agriculture, pyroclastic currents, landslides, lahars, and tsunamis in coastal or island settings. Eruptions can deposit new land and soils but may threaten nearby populations and climate temporarily by injecting aerosols and gases into the atmosphere.

Volcanic activity is monitored by seismometers, ground deformation measurements, gas sensors, and satellite observations. Observations guide hazard assessments and evacuations. Notable volcanoes include Mauna Loa and Kilauea in Hawaii, Mount Etna in Italy, Vesuvius in Italy, Eyjafjallajökull in Iceland, Krakatoa in Indonesia, and Mount Pinatubo in the Philippines.