Extrusive Landforms (detailed)

  • Formation
  • Morphology
  • Magma type
  • Plate boundary
  • Examples
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  • Created by: Max123
  • Created on: 19-03-13 13:29
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Type of Lava Plateaux Shield volcano Composite volcano Dome volcano Caldera volcano
Formation Lava Plateaux are formed during It is built up due to Built up of They have steep, convex They form due to highly explosive
fissure eruptions, where basalt successive flows of basaltic alternating layers sides due to acidic, volcanic activity- the magma chamber
lavas pour out of cracks in the lava. Due to the low of lava flows and andesitic lava, which is too gradually empties until there is no
surface (fissures) rather than from viscosity and high ash. The have a viscous to flow far from magma left to support the roof of the
a central vent; as the lava is runny temperatures, the lava conduit system the source and it soon chamber. The mountain summit
(low viscosity) and takes a long flows over wide distances through which cools and solidifies. Domes therefore collapses into the chamber
time to cool, it travels long away from the vent; the lava magma rises to the often plug vents as lava creating a caldera. The bowl-shaped
distances from the fissure; these gradually cools as thin, surface at the solidifies, this may lead to depression often fills with water,
features are layered structures gently dipping sheets of central vent in the the formation of a forming a lake. If new magma continues
caused by the accumulation of lava volcanic rock crater at the summit. secondary vent on the side to rise, small, new volcanic cones may
over a series of lava flows, forming Lava may flow from of the volcano due to the form within the caldera. Fresh magma
as a broad plateaux rather than fissures on the flank build up of pressure. Due may enter the magma chamber causing
piling up as a volcanic mountain. forming secondary to the plugging of vents, it to re-inflate and the caldera floor to
cones. (As magma gasses are trapped and dome up as a Resurgent Caldera -
solidifies in the pipe eruptions are often when these erupt, they can be the most
system, it explosive in nature. destructive natural phenomenon on
strengthens the earth.
Morphology It is flat / very gentle sloping and They have gentle sloping They are often very They are dome shaped They have large, steep walled basin
a layered structure (layers of lava cones and a wide base that large structures accumulations of volcanic shaped depressions and often have a
from series of eruptions over is not particularly high. It with steep and fairly rock and features include lake inside the crater. They may have
time.)It is featureless (usually consists of layers of basaltic symmetrical sides; steep, convex sides, a new volcanic cones growing inside.
limited soil / vegetation cover) lava they consist of narrow base and high
alternating layers of cones. They may have
acidic lava and ash secondary cones.
and often have
secondary cones.
Magma type Basaltic Basaltic Andesitic Andesitic Rhyolitic
Type of N/A Common at constructive Destructive Destructive boundaries. Convergent margins or continental
plate margins and hot spots (e.g. boundaries. hotspot locations.
boundary Hawaiian Islands)
Example The Deccan Plateau (India) is a The Belknap Volcano, Mount St Helens, Mount Pelée in Martinique. Lake Toba (convergent margin) and the
huge expanse of lava covering an Oregon. the Cascade region Yellowstone Caldera (continental
area of 700,00km2 and consisting of North West hotspot.)
of 29 lava flows which have America.

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Source http://library.thinkquest.org/1745 http://www.volcanodiscove http://geography-si http://volcano.oregonstat http://www.tulane.edu/~sanelson/geo
7/volcanoes/features.plateaus.ph ry.com/belknap.html te.co.uk/pages/phys e.edu/book/export/html/ l204/volclandforms.htm
p ical/earth/helen.…read more


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