Types, Processes and Landforms of Plate Margins

• What are the 3 different types of plate boundaries?

  • Constructive - plates move apart
  • Destructive - plates move together
  • Conservative - plates sliding past each other
• Both volcanic eruptions and earthquakes occur at Constructive plate boundaries.
• What are the 2 landforms that constructive margins create?


  Ocean Ridge and Rift Valley
• An ocean ridge forms when the diverging plates are under the ocean.

  As the plates move apart, magma rises up to fill the gap and this accumulates over time to become taller and wider.
• What is an example of an Ocean Ridge?


  Mid Atlantic Ridge
• A rift valley forms when the diverging plates are beneath the land.

  As the plates move apart, the crust stretches and fractures. Areas of crust drop down between faults to create a valley.
• What is an example of a Rift Valley?


  East African Rift Valley
• What are deep sea trenches?

  Long, narrow depressions in the ocean floor
• What is the depth range of deep sea trenches?

  Over 6 km and up to 11 km
• Where are trenches typically found?

  Adjacent to land areas and associated with island arcs
• How is the shape of a trench typically characterized?

  Asymmetric, steep side towards the land mass
• What is an example of a plate boundary involving a trench?

  The boundary between the Nazca plate and South American plate
• What is the Benioff Zone?


  The zone of earthquakes along the subduction slab
• What happens to the oceanic plate at a subduction zone?

  The denser oceanic plate subducts under the continental plate
• What geological feature is formed in the subduction zone?

  Deep ocean trenches
• What types of geological events occur at this type of plate boundary?

  Violent volcanic eruptions and earthquakes
• What type of volcanoes are typically formed at oceanic-continental convergent boundaries?

  Steep-sided, composite volcanoes
• What types of lava flows are associated with these volcanoes?

  Andesitic and rhyolitic lava flows
• What geological structures are formed at oceanic and continental convergent plate boundaries?

  Fold mountains
• What is an example of fold mountains formed at an oceanic-continental destructive boundary?

  The Andes
• How are deep sea trenches formed?

  By oceanic plate bending and subducting
• What is an example of a deep sea trench?

  Peru-Chile trench
• How are fold mountains formed?

  By compression and deformation of continental plates
• What type of mountain ranges do fold mountains form?

  The highest of the world’s mountain ranges
• What is the structure of fold mountains?

  Long, narrow belts with parallel ridges and valleys
• What is the composition of the main fold range?

  A series of smaller ranges with plateaus