volcanos

Volcanos are openings in Earth's crust that allow magma and volcanic materials to escape to the surface. They form when magma collects in reservoirs and pressure builds until it is released through vents. The term volcano can refer to the vent, the eruption, or the mountain-like structure that often grows around the vent. The standard plural is volcanoes, but volcanos is also used.

Most volcanos occur at tectonic plate boundaries or in intraplate regions known as hot spots. At divergent boundaries, such as mid-ocean ridges, upwelling magma creates basaltic lava and broad shield volcanoes. At convergent boundaries, where oceanic crust subducts, magmas are more silica-rich and viscous, leading to stratovolcanoes with explosive eruptions. Hot spots produce a range of volcano types, exemplified by the Hawaiian volcanoes.

Volcanic activity ranges from effusive eruptions that emit lava flows and form domes to explosive eruptions that eject ash clouds, pumice, and volcanic bombs. The combination of low or high magma viscosity and dissolved gases largely determines eruption style. Lava flows can bury terrain; ash clouds can affect air travel and climate; pyroclastic flows and lahars can devastate nearby areas.

Volcanic hazards include lava flows, ashfall, pyroclastic flows, lahars, landslides, volcanic gases, and, in some cases, tsunamis triggered by eruptions or flank collapses. Monitoring networks track seismicity, ground deformation, gas emissions, and satellite observations to provide early warnings.

Notable volcanoes include Mauna Loa, Kilauea, Mount St. Helens, Mount Vesuvius, and Eyjafjallajökull. Eruptions can create new land, alter landscapes, and influence climate through the emission of aerosols.