VOLCANISM

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VOLCANISM

• GRADE 10

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Landforms associated with volcanic activities

• Plutonic rocks resulting in intrusive landforms
• Extrusive landforms

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Landforms of igneous intrusions

• Commonest intrusive landforms are sills and
  dykes.
• A horizontal intrusion along a bedding plane is
  called a sill.
• Intrusions which are injected vertically are
  referred to as dykes.
• Examples of igneous intrusions are the liths
  ,laccoliths, phacoliths, lopoliths,and
  batholiths.
• A laccolith is a large blister with a dome shaped
  upper surface and a conduit like pipe below it.
• A lopolith is a an igneous intrusion of a saucer
  shape.
• A phacolith is a lens- shaped mass of igneous
  rocks.
• A batholiths is a huge mass of igneous rocks,
  usually granite.

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A diagram showing an intrusive landforms of
igneous intrusions in volcanic regions
volcano
sill
dyke
batholiths
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Types of lava

• 1.Basic lava- very hot and highly fluid.
• Dark colored like basalt
• Flow quietly and not explosive
• 2.Acid lavas highly vicious with a high melting
  point
• Light colored, of low density
• High silica percentage
• Flow slowly and seldom easily solidify

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Types of volcanoes

• Three types namely
• Extinct
• Dormant
• Active

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Extinct volcanoes

• Volcanoes that have not erupted in historical
  times
• They retain the features of a volcanoes

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Dormant volcanoes

• Those that have been known to erupt
• They show signs of possible eruptions

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Active volcanoes

• These frequently erupt or they at least erupted
  in recent times

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Extrusive landforms

• Determined by nature and composition of lava and
  other ejected materials
• Lava produces extensive lava plains and basaltic
  plateaux
• Highly fluid lava build up lava domes or shield
  volcanoes
• Less fluid lavas violently form ash and cinder
  cones

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Ash and cinder cone
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Lava domes or shield volcanoes
Lava from shield volcano
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A caldera
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Distribution of volcanoes in the world
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Exercise

• 1.what are three types of volcanoes?
• 2.name the two types of lava.
• 3.what are the main intrusive landforms, list at
  least three?
• 4.what is the difference between intrusive
  landforms and extrusive landforms.