The Main Types of Volcano
February 23, 2026
Volcanoes come in a handful of basic shapes, and the shape is set almost entirely by the magma: how much silica it contains, how much gas, and how runny it is. Here are the main types, from gentlest to most violent.
Shield volcanoes
Broad, gently sloping domes built from thousands of thin, runny basalt lava flows. The magma is low in silica and hot, so gas escapes easily and eruptions are usually lava fountains and flows rather than explosions. Mauna Loa in Hawaii is the largest volcano on Earth by volume — a shield about 100 km across. Iceland’s volcanoes and Nyamuragira in the Congo are others.
Stratovolcanoes (composite volcanoes)
The classic steep, symmetrical cone, built in alternating layers of lava and explosive debris. These form above subduction zones from stickier, gas-rich, silica-intermediate magma. They can sit quiet for centuries and then erupt violently, with ash columns, pyroclastic flows and mudflows (lahars). Fuji, Mayon, Cotopaxi, Vesuvius, Mount St. Helens — most of the famous “volcano-shaped” volcanoes are stratovolcanoes, and most of the deadly eruptions in history came from them.
Calderas
Not a mountain but a hole. When a very large eruption empties a shallow magma chamber, the roof of the chamber collapses, leaving a basin kilometres across. Crater Lake in Oregon fills a caldera left when Mount Mazama collapsed about 7,700 years ago. Yellowstone, Santorini, Campi Flegrei near Naples, and Taupō in New Zealand are calderas. The largest — “supervolcanoes” — can produce VEI 8 eruptions, though none has in recorded history.
A caldera can stay dangerous for a long time. Campi Flegrei, which last had a major eruption in 1538, has been slowly inflating and producing earthquake swarms for decades.
Cinder cones and fissure fields
Cinder (scoria) cones are the smallest common volcano: a single steep pile, usually under 300 m high, built in weeks to years from frothy lava blobs thrown out of one vent. Parícutin in Mexico famously grew in a farmer’s field starting in 1943.
Fissure vents and volcanic fields erupt from long cracks rather than a central vent, feeding lava flows and rows of small cones. Iceland’s 2021–2024 Reykjanes eruptions and the 1783 Laki eruption are fissure eruptions; the volcanic fields around Auckland and Flagstaff are the same style spread over a wide area.
Sources
- U.S. Geological Survey — Volcano Hazards Program: “Types of volcanoes”, “Principal types of volcanoes”.
- Global Volcanism Program, Smithsonian Institution — “Volcano types”, Volcanoes of the World.
- Sigurdsson, H. et al. (eds.) (2015). The Encyclopedia of Volcanoes, 2nd ed. Academic Press.