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