Volcanoes: Formation, Features, and Eruptions

Volcanoes and volcanism

Volcanoes are vents or fissures in a planet’s crust through which lava, volcanic ash, and gases escape from underground magma. On Earth, most volcanoes occur at divergent or convergent tectonic plate boundaries, especially along mid-ocean ridges and subduction zones. Volcanism can also occur in continental rifts and at hotspots caused by rising mantle plumes, such as the Hawaiian hotspot. Volcanoes are classified as active, dormant, or extinct according to their eruptive history and likelihood of future activity. Volcanoes vary greatly in structure and behavior. Major types include fissure vents, shield volcanoes, lava domes, cinder cones, stratovolcanoes, caldera volcanoes, supervolcanoes, submarine volcanoes, and subglacial volcanoes. Eruptions may be gentle and effusive, producing fluid basaltic lava, or explosive when viscous, gas-rich magma fragments into ash and pyroclastic material. Volcanic activity also produces hydrothermal features such as fumaroles, geysers, hot springs, and mud volcanoes. Large eruptions can cause widespread destruction, climatic cooling, volcanic winters, and famine, while volcanic soils can later support fertile ecosystems.

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Plate tectonics and volcanic activity

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