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Chapter 12- Volcanoes
Volcanoes
23
Geology
Undergraduate 1
04/10/2010

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Term
Asthenosphere
Definition
is the main source of magma.
Term
Lava
Definition
is eruptes magma.
Term
Difference b/w lava and magma
Definition
Magma is molten rock below Earth's surface and lava is magma after it erupts.
Term
What are Volcanoes?
Definition
A hill or mountain contructed from the accumulation of lava and other erupted materials.
Term
Central eruptions
Definition
Magma periodically empties to the surface through a pipelike conduit in repeated cycles.
Term
Fissure eruptions
Definition
Lava that can erupt from vertical cracks (fissures) and other vents on the flanks of a volcano.
Term
Basaltic Lava
Definition
a lava in mafic composition that has a low silica content, erupts at high temperatures, and flows readily. mostly gentle eruptions.
Term
Andesitic Lava
Definition
A lava in intermediate composition that has a higher silica, erupts at lower temperatures, and is more viscous. Eruptions along many subduction zones.
Term
Rhyolitic Lava
Definition
The lava in felsic composition that is richest in silica, making it the stickiest and least fluid kind of lava. It erupts in temperatures of only 600-800 degree Celsius.
Term
What are Vesicles?
Definition
Gas cavities created by when pressure is released, water vaporand other dissolved gases escaping from lava.
Term
What are Pyroclasts?
Definition
Fragmentary volcanic rocks ejected into the air.
Term
Central Eruptions: What are Shield Volcanoes?
Definition
They are built up by the accumulation of thousands of thin basaltic flows that spread as gently sloping sheets.
Term
CE: What are Cinder-Cone Volcanoes?
Definition
They are formed when ejected material is deposited as layers that dip away from the crater at the summit.
Term
CE: What are Stratovolcanoes?
Definition
are built from alternating layers of pyroclastic material and lava flows.
Term
CE: What are Craters?
Definition
They are a bowl-shaped pit, that is found at the summit of most volcanoes, centered on the vent.
Term
CE: What are Calderas?
Definition
A large, steep-walled, basin-shaped depression formed after a violent eruptions in which large volumes of magma are discharged, when the overlying volcanic structure collapses catastrophically through the roof of the emptied magma chamber.
Term
Fissure eruptions: What are flood basalts?
Definition
Successive flows often pile up into immense basaltic lava plateaus.
Term
FE: What are ash-flow deposits?
Definition
Fissure eruptions of pyroclastic materials on continents have produced extensive sheets of hard volcanic tuffs.
Term
What is a geyser?
Definition
A geyser is a vent in Earth's surface that periodically ejects a column of hot water and steam.
Term
How can volcanism cause global cooling?
Definition
The sulfuric gases from volcanism form an aersol that blocks enough of the Sun's radiation from reaching Earth's surface to lower global temperatures.
Term
What are Mantle Plumes?
Definition
A narrow, cylindrical jet of hot, solid material rising from deep within the mantle and though to be responsible for intraplate volcanism.
Term
What are hot spots?
Definition
A volcanic center found at the beginning of progressively older aseismic ridges or within a continent far from a plate boundary.
Term
What is a large igneous province?
Definition
They are large volumes of predominatly mafic extrusive and intrusive rocks whose origins lie in processes other than normal seafloor spreading.
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