Week 11: Intra-plate Tectonics and Plate Boundary Processes

• Hot Spot Volcanoes

  • Formed when there is a plume of hot, rising mantle material directly under the crust.
  • This then pushes through the crust and creates a hot spot volcano.
  • As the plate moves, the hot spot stays stationary, this creates a chain of volcanoes that show a trace in the previous positions of the plate relative to the hot spot.
  • An example of this is the Hawaiian Islands that are formed through this process
• Island Arc Volcanoes

  • Long chains of active volcanoes that are formed on the boundary of subduction zones.
  • An example of this is the Pacific plate being subducted under the North American plate, between Russia and Alaska.
  • The subduction of the dense Pacific Plate leads to an increase of heat and pressure, as the plate begins to melt magma is created and begins to ascend.
  • This leads to the production of volcanic island arcs. The density and distribution of island arc volcanoes shows the nature of the subduction boundary
• Intra Plate Stresses- Australia

  • Stress generated through the stress and strain created at plate boundaries. Indian continent is moving northwards quicker than Australia, causing a build-up of stress across the continent
  • Australia is also colliding with PNG, leading to the formation of the New Guinea Highlands, this slows Australia’s motion and leads to more stress (India)
  • Australia is moving northwards due to the ridge push effect from the Pacific-Antarctica Ocean ridge and the slab pull affect, these stresses travel to the continents interior where they are released as earthquakes
• Edge Driven Convection

  • Western Victoria is known as the newer volcanics plain. The presence of these volcanoes can be explained due to upwelling in the mantle due to edge driven convection of the continental shelf
  • The circulation edge driven convection is driven by temperature and density differences near the edge of tectonic plates, due to thicker continental plate there exists a step in the lithosphere, this leads to the stirring of mantle material like upwelling behind a boat. This leads to mantle plumes creating volcanoes. Like those seen in Western Victoria
  • DRAW