Tectonic Landforms

• ocean trench

  • when oceanic plate is subducted
  • causing seafloor and lithosphere to bend and form a steep, v shaped depression
  • long trench around 10km deep, runs parallel to fold mountains
  • steepest side on continental side
• volcanic island arcs

  • subducted oceanic plate partially melts
  • magma collected in magma chambers rises through cracks and fissures to form strato volcanoes
  • E.g. Aleutian Islands
• fold mountains

  • due to compression of continental plate at oceanic-continental boundary e.g. The Andes
  • this crustal thickening causes downward and upward sloping strata to form
  • material that is scraped off subducting oceanic plate is deposited on leading edge of continental plate
  • forming an accretionary wedge
  • this material also contributes to mountain building
• oceanic ridges

  • can be up to 3km high
  • divergent plate boundaries
  • seafloor spreading leads to production of new ocean crust
  • as plates separate, molten rock rises to seafloor, producing volcanic eruptions of basalt