an opening in Earth's crust where magma, gases, and ash reach the surface
formed at plate tectonics boundaries: subduction zones, divergent ridges, and hotspots
types: shield (broad, effusive), stratovolcano (steep, explosive), cinder cone, caldera
the Ring of Fire around the Pacific ocean contains 75% of active volcanoes
eruptions release CO2, SO2, and aerosols, connecting to the carbon cycle and climate
volcanic soils (andisols) are among the most fertile on Earth
cyber valley sits on volcanic soils in Bali, enriched by centuries of eruptions
major eruptions alter global temperature: Tambora 1815 caused the "year without a summer"
volcanic islands create isolated ecology and drive evolution (Galapagos, Hawaii)
geothermal energy from volcanic systems provides renewable power (Iceland, Indonesia)
lahars, pyroclastic flows, and tephra are primary hazards