Thursday 25 August 2011

Different type of volcano's




Dome Volcano:
In volcanology, a lava dome is a roughly circular mound-shaped protrusion resulting from the slow extrusion of viscous lava from a volcano. The geochemistry of lava domes can vary from basalt to rhyolite although most preserved domes tend to have high silica content.
Lava domes are dynamic structures that evolve over time undergoing various processes such as growth, collapse, solidification and erosion.

Shield Volcano:
A shield volcano is a type of volcano usually built almost entirely of fluid lava flows. They are named for their large size and low profile, resembling a warrior's shield. This is caused by the highly fluid lava they erupt, which travels farther than lava erupted from more explosive volcanoes. This results in the steady accumulation of broad sheets of lava, building up the shield volcano's distinctive form.
Shield volcanoes are built up by effusive eruptions, which flow out in all directions to create a shield like that of a warrior.

Cone Volcano:
A cinder cone or scoria cone is a steep conical hill of volcanic fragments that accumulate around and downwind from a volcanic vent.
Many cinder cones have a bowl-shaped crater at the summit. Lava flows are usually erupted by cinder cones, either through a breach on one side of the crater or from a vent located on a flank.
Cinder cones are commonly found on the flanks of shield volcanoes.

Composite Volcano:
Composite volcanoes, also called strato volcanoes, are formed by alternating layers of lava and rock fragments. This is the reason they are called composite.
Between eruptions they are often so quiet they seem extinct. To witness the start of a great eruption requires luck or very careful surveillance.
Composite volcanoes usually erupt in an explosive way. This is usually caused by viscous magma. When very viscous magma rises to the surface, it usually clogs the craterpipe, and gas in the craterpipe gets locked up. Therefore, the pressure will increase resulting in an explosive eruption.


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