Volcanoes

Volcanoes form where heated material escapes from the Earth's crust.

Type of eruption named for

Features structure; ejection; effusion

gas/silica content of lava

Hawaiian

Hawaiian island shield volcanoes

spatter cones and ramparts; very broad, flat lava cones; very weak ejection of fluid blobs, cow-dung bombs and spatter, very little ash; followed by often extensive flows of low viscosity (fluid) lava low gas/low silica
Basaltic flood spatter cones and ramparts; very broad, flat lava cones, lava plains; very weak ejection of fluid blebs and cow-dung bombs and spatter, very little ash; followed by voluminous, wide-spread flows low gas/low silica

Strombolian

Stromboli

cinder cones; weak to violent ejection of pasty fluid blebs, spherical to fusiform bombs; cinder; small to large amounts of glassy ash; thicker, less extensive flows of moderately fluid lava; flows may be absent ↓ increasing gas/higher silica

Vulcanian

Vulcano

Soufriere Hills

ash cones, block cones, block-and-ash cones; moderate to violent ejection of solid hot fragments of new lava; essential, glassy to lithic, blocks and ash, pumice; lava viscous, so flows commonly absent, thick and stubby if present, ash flows rare

Peleean

Mt. Pelee

ash and pumice cones; domes; explosive activity like Vulcanian, commonly with glowing avalanches; domes and/or short, very thick flows of viscous lava; flows may be absent

Plinian

Pliny the Elder, who died during the eruption of Vesuvius

widespread pumice lapilli and ash beds; generally no cone-building; ejection of large volumes of ash, with accompanying caldera collapse, ejecta are glassy ash and pumice; magma very viscous, so ash flows, small to very luminous, or effusive activity may be absent
Rhyolitic flood flat plain, or broad, flat shield, often with caldera; relatively small amounts of ash projected upward into the atmosphere; ejecta are glassy ash and pumice; viscous magma, so effusive activity confined to relatively small amounts of ash projected upward into the atmosphere Rhyolite
Ultravulcanian block cones; block-and-ash cones; weak to violent ejection of solid fragments of old rock; ejecta are accessory and accidental block and ash; no magma and no lava effusion
gas eruptions continuous or rhythmic gas release at vent; no ejecta or very minor amounts of ash, no magma
fumarolic generally no structure, rarely very small ash cones; no ejecta or rarely very minor amounts of ash; no magma, nonexplosive weak to moderately strong long-continued gas discharge

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