Vulcanicity 

  • Vulcanicity is the process through which gases and molten rock are either extruded on the earth’s surface or intruded into the earth’s crust.
  • Magma is the molten rock originating from the upper plastic layer of the mantle. When it gets to the surface and loses its gases, it is known as lava.
  • Pyrocrasts are the ashes, cinders and small particles of magma during an explosive volcanic eruption.

Intrusive Igneous Landforms

  • Batholiths: Largest mass of magma crumbling in the crust. An example is the Stone Mountain of Georgia.
  • Sills: Sheets of magma intruded onto bedding planes of sedimentary rocks.
  • Dykes: Wall like features formed when magma cuts across several bedding planes.
  • Pipes: The stems of volcanoes.
  • Laccoliths: Dome shaped layers of magma formed when magma encounters rock more resistant at its sides than its center.
  • Lopoliths: Bowl shaped layers of magma formed when magma encounters rock more resistant at its center than its sides.

Extrusive Igneous Landforms

  • Composite Volcano: A cone shaped feature formed by alternating layers of lava and ash. Sometimes, a volcano erupts so violently, its crater is blown off enlarging the top depression. This is then known as a caldera. If filled with water, it is known as a Caldera Lake.
  • Lava Plateau: This is an upland with a generally level summit made up off successive layers of lava and ash.

Types of Volcanoes

  • Active: This is a volcano that has erupted within the last 500 years and still shows signs of activity.
  • Dormant: This is a volcano that has not erupted within the last 500 years but still shows signs of activity such as hot springs. An example is Mt. Kilimanjaro.
  • Extinct: This is a volcano that has not erupted within the last 500 years and shows no signs of activity. An example is Mt. Kenya.

Exogenetic Processes

  • These are processes that take place on the earth’s surface.
  • They are subdivided in two categories:
    • Processes of degradation
    • Processes of aggradation
  • Processes of aggradation are those that build up material. Processes of degradation are those that destroy what has been built up by endogenetic/aggradation processes.
  • The destruction of the landscape is known as denudation. There are three processes involved:
    • Weathering
    • Erosion
    • Transportation
  • The exogenetic processes require the use of agents such as running water, ice and wind.

https://www.thestudentroom.co.uk/revision/geography/vulcanicity-and-landforms

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