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Extrusive volcanism ­ a summary

Landform / structure Description Process /notes



A volcano is an opening, or rupture, in a
planet's surface or crust, which allows hot
magma, ash and gases to escape from below
the surface. The word volcano is derived from
the name of Vulcano island off Sicily…

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A pyroclastic flow (also known scientifically
as a pyroclastic density current is a common
and devastating result of certain explosive
Pyroclastic flow volcanic eruptions. The flows are fast-moving
currents of hot gas and rock (collectively
known as tephra), which travel away from the
volcano at speeds generally as great as…

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Volcanic cones are among the simplest
volcanic formations in the world. They are built
by ejecta from a volcanic vent, piling up
around the vent in the shape of a cone with a
Volcanic cones central crater. Volcanic cones are of different
types, depending upon the nature and size of…

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it lands, the individual deposits are very
irregular in shape and weld together as they
cool, and in this way particularly differ from
cinder and ash. Spatter cones are typical of
volcanoes with highly fluid magma, such as
those found in the Hawaiian Islands.


An ash cone is composed of…

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Cinder cones rarely rise more than 300 to 750
m or so above their surroundings, and, being
unconsolidated, tend to erode rapidly unless
further eruptions occur. Cinder cones are
numerous in western North America as well as
throughout other volcanic terrains of the
world. Parícutin, the Mexican cinder cone
which…

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plateaus and mountain ranges. Flood basalts
have erupted at random intervals throughout
geological history and are clear evidence that
Flood basalts the Earth undergoes periods of enhanced
activity rather than being in a uniform steady
state. One explanation for flood basalts is that
they are caused by the combination of…

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A stratovolcano, sometimes called a
composite volcano is a tall, conical volcano
with many layers (strata) of hardened lava,
tephra, and volcanic ash. Stratovolcanoes are
Composite (strato) or characterized by a steep profile and periodic,
andesitic explosive eruptions. The lava that flows from
volcano stratovolcanoes tends to be viscous; it…

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Cañadas Caldera Teide, Tenerife and the
Caldera de Taburiente, La Palma, both in the
Canary Islands. When he published his memoirs
he introduced the term "caldera" into the
geological vocabulary. A collapse is triggered
by the emptying of the magma chamber
beneath the volcano, usually as the result of a…

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