andesitic lava
a lava of intermediate composition that has a higher silica content than basalt, erupts at lower temperatures, and is more viscous
ash-flow deposit
an extensive sheet of hard volcanic tuff--any volcanic rock lithified from pyroclasts
basaltic lava
a lava of mafic composition that has low silica content, erupts at high temperatures, and flows readily
caldera
a large, steep-walled, basin-shaped depression formed after a violent eruption in which large volumes of magma are discharged, when the overlying volcanic structure collapses catastrophically through the roof of the emptied magma chamber
crater
1) a bowl-shaped pit found at the summit of most volcanos, centered on the vent; 2) a depression caused by the impact of a meteorite
diatreme
a volcanic vent formed by the explosive escape of gases and often filled with breccia
fissure eruption
a volcanic eruption emanating from an elongate fissure rather than a central vent
flood basalt
an immense basaltic lava plateau extending many kilometers in flat, layered flows originating from fissure eruptions
hot spot
a volcanic center found at the beginning of progressively older aseismic ridges or within a continent far from a plate boundary (hypothesized to be the surface expression of a mantle plume)
hydrothermal activity
the circulation of water through hot volcanic rocks and magmas, producing hot springs and geysers on the surface
lahar
a torrential mudflow of wet volcanic debris produced when pyroclastic or lava deposits mix with rain or the water of a lake, river, or melting glacier
large igneous province
(LIP) a voluminous emplacement of predominantly mafic extrusive and intrusive igneous rock whose origins lie in processes other than "normal" seafloor spreading. LIPs include continental flood basalts, ocean basin flood basalts, and aseismic ridges
mantle plume
a narrow, cylindrical jet of hot, solid material rising from deep within the mantle and thought to be responsible for intraplate volcanism
pyroclast
a volcanic rock fragment ejected into the air during an eruption
rhyolitic lava
the lava that is richest in silica, making it the stickiest and least fluid kind of lava; it erupts at temperatures of only 600 degrees to 800 degrees Celsius
shield volcano
a broad, shield-shaped volcano many tens of kilometers in circumference and more than 2 km high built by successive flows of fluid basaltic lava from a central vent
stratovolcano
a concave-shaped volcano containing alternating layers of lava flows and beds of pyroclasts
volcanic geosystem
the total system of rocks, magmas, and interactions needed to describe the entire sequence of events from melting to eruption
volcano
a hill or mountain constructed from the accumulation of lava and other erupted materials