Volcano Revision Guide

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  • Created on: 28-03-13 19:44
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Volcano Revision
A volcano is a landform that develops around a weakness in the Earth's crust, from which
molten magma, disrupted from pre-existing volcanic rock, and gases are ejected or
Types of volcano:
Central vent type ­ with a single pipe
Fissures - where magma is extruded along a linear fracture.
Calderas ­ they have low lying craters created as a result of subsidence or collapse
following an eruption.
EXTINCT VOLCANOES: isn't erupting now and will never erupt in the future.
DORMANT VOLCANOES: isn't erupting now but has erupted since written records begun
(the last 200 years), and is likely to erupt in the future
ACTIVE VOLCANOES: one that is erupting or expected to erupt in the near future.
The distribution of volcanoes:
Restricted to zones where there is a supply of magma from the earths interior
Destructive and conservative plate margins (interplate)
Hotspots within plate interiors (intraplate)
The risk of volcanic eruption is extremely complex to forecast as it is determined by several
different physical and human factors:
Physical Human
Eruption column height Population density
Eruption rate Presence/absence of alert systems.
Volume of ejecta Infrastructure
Duration of continuous blasts Community preparedness
Type of lava (depends on silica content)
Primary effects of a volcanic event:
Tephra (solid material of varying grain size) ejected into the atmosphere.
Pyroclastic flows (gas charged, high-velocity flows).
Lava flows
Volcanic gases e.g. carbon dioxide, carbon monoxide, sulphur dioxide etc.
Secondary effect of a volcanic event:
Lahars ­ volcanic mud flows
Flooding ­ under-ice volcanic activity can cause catastrophic melting.

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Volcanic landslides
Climate change ­ the ejection of huge quantities of volcanic debris can cause a
change in average global temperatures.
More than 500 million people live in areas at risk from volcanic hazards. Such land
often has richer soils and a better climate than the surrounding region.
A supervolcano has the potential to cause global devastation. The first Yellowstone event
(2.…read more


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