Deep Sea Trenches

  • The ocean trenches are narrow depressions in the sea. These trenches form the deepest points in the ocean and are the lowest points on earth.
  • Ocean Trenches are formed at a place of plate boundary which is known as the subduction zone. It experiences frequent earthquakes.
  • The trenches can be very long up to thousands of kilometres and they may be parallel to island arc volcanoes. Forms when an oceanic plate hits another oceanic plate, or an oceanic plate strikes with continental plate.
  • Oceanic plates are made of basalt which is a denser rock while continental plates are formed up of granite which is not as dense as the basalt.
  • When one plate hits another plate, the denser plate between the two of them sinks in the mantle. The place where this plate sinks will create a deep trench on that spot of ocean. They are associated with a chain which is known as island arc.