Ch 1.3 What are the major landforms found at the plate boundaries? Flashcards
What are the four major zones of divergent plate boundaries?
- Mid-Atlantic zone
- Mid-Indian zone
- Antarctic zone
- South-east pacific zone
What are formed when oceanic plates diverge from each other?
When two oceanic plates (South American Plate and African Plate) diverge from each other. They are driven by rising convection currents in the asthenosphere. Tensional force may continue to move apart and create a fissure. Magma flows through the fissure. Lava cools and solidifies to form new crust. With the low density, the crust rises above the existing crust and form a mid-oceanic ridge (i.e. Mid-Atlantic Ridge). When magma rises through the cracks, vulcanicity occurs. Submarine volcanoes formed. Repeated eruptions raise the height of the submarine volcanoes. When they rise above the sea, volcanic islands are formed. Sometimes, the rate of seafloor spreading is different at different ocean floors, and transform faults may form.
Do submarine volcanoes and volcanic islands stay where they are after a million of years? Why?
No, they have moved away from the mid-oceanic ridge. As plates continue to diverge, ridge push and slab pull will cause the plates to be dragged in opposite directions. Submarine volcanoes and volcanic islands are carried away from the mid-oceanic ridge. With the supply of magma, submarine volcanoes and volcanic islands become extinct.
What landforms will occur when there are two continental plates in divergent plate boundary?
When two continental plate (Nabian Plate and Somalian Plate) move apart. They are driven by rising convection currents. Tensional force may continue to move apart and cracks are developed. Normal fault occurs. If the plates sink and formed a flat-bottom valley, it is called the rift valley (East African Rift Valley). Due to the reducing pressure on the asthenosphere, rock thus melts and rises as magma which rises through the cracks. Repeated volcanic eruptions build up volcanoes.
