Summary
Highlights
Volcanoes are openings or vents to the hot interior of the planet. There are about 1,500 active volcanoes worldwide, with nearly 90% located in the Ring of Fire around the Pacific Ocean.
Volcanoes often form where tectonic plates interact. Friction from shifting plates melts the Earth's crust, liquefying rock into magma, which then erupts through rifts.
Once magma escapes, it's called lava. Runny lava forms gentle shield volcanoes, while thick, sticky lava builds steeper composite volcanoes that can erupt violently. Hawaii's Kilauea is a continuously erupting shield volcano formed over a hotspot.
Living near volcanoes can be hazardous. The 79 AD eruption of Mount Vesuvius buried Pompeii with superheated ash, poisonous gas, and rocks in a deadly pyroclastic flow, claiming 2,000 lives.
Despite their dangers, volcanoes have created 80% of Earth's surface and contributed to the air we breathe. They also produce rich soil for farming, and their subsurface heat can be harnessed for geothermal energy.