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The Dynamic Earth: PLATE TECTONICS Types of Plate Boundaries EQ: How does plate tectonics shape the earth’s surface? Types of Plate Boundaries There are approximately 20 plates found on the Earth’s crust. These plates are moving in relation to one another in a process known as PLATE TECTONICS. Review What is the What are the 2 lithosphere? types of crust? Convergent Boundaries A convergent boundary is a boundary between two lithosphere plates that are moving toward each other, or converging. Convergent Boundaries Earth has 2 types of crust on it’s surface; Continental and Oceanic Crust. There are 3 different types of convergent boundaries and processes involved depending on the types of crust involved. These processes are known as either Subduction or Collison. Convergent: Ocean to Ocean 2 oceanic plate colliding! Volcanic Island Arcs are a feature formed at these boundaries. Current Example: the islands of Hawaii Convergent: Continent to Continent 2 Continental plates are colliding! If two plates each carrying continents collide, they become welded into a single, larger continent. Convergent: Continent to Continent Feature: The collision causes the crust at the boundary to be pushed upward into a mountain range. Current Example: The world’s tallest mountains are known as the Himalayas. Convergent: Continent to Ocean 1 Oceanic plate and 1 Continental plate collide. When an oceanic plate collides with a continental plate, the oceanic plate sinks under the continental plate. This is because the oceanic plate is made of basalt which is more dense than the granite composed continental crust. Convergent: Ocean to Continent When a continental plate and an oceanic plate collide common features include: volcanoes along the coast line deep-sea trenches Convergent: Ocean to Continent Current Examples of volcanoes: Mt. St. Helens, Mount Katmai, Mount Pinatubo, Montserrat, Mount Pelee Divergent Boundaries A divergent boundary is a boundary between two lithosphere plates that are moving apart. They are sometimes called spreading centers. Divergent Boundaries: Mid Ocean Ridges In a process called sea floor spreading, molten rock forces its way upward through cracks, or rifts. The molten rock hardens into new oceanic crust. Divergent Boundaries Hydrothermal vents and the mid-ocean ridge are found at divergent boundaries. Divergent Boundaries Examples: Mid- The Great Rift Valley in East Africa Atlantic Ridge Great Rift Valley Transform Boundaries Transform Boundaries A transform boundary is a boundary between two plates that are sliding past one another. Current Example: San Andreas Fault- moving about 5 cm/year. Transform Boundaries The main feature of transform boundaries are… EARTHQUAKES Observe animations of processes that occur along plate boundaries. Plate Tectonics Map - Plate Boundary Map