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Plate Boundaries Where Plates Meet Plate Boundaries Tectonic plates move and collide with each other. A plate boundary is where the edges of two tectonic plates meet. There are 3 different types: 1. Divergent 2. Convergent 3. Transform 1. Divergent Where two plates move apart. 2. Convergent Where two plates push together. 3. Transform Where two plates scrape by each other. 1. Divergent Boundaries A divergent boundary is where 2 plates pull apart. As the plates pull apart, a deep gap called a rift valley forms. rift valley 1. Divergent Boundaries Divergent boundaries can occur underwater. Below the oceans, mid-ocean ridges are the result of huge divergent boundaries. The world’s longest mountain chain is the Mid-Atlantic Ridge, found below the Atlantic Ocean. Here, the North and South American plates move away from the Eurasian and African plates… Mid-Atlantic Ridge North American plate South American plate Eurasian plate African plate Iceland Iceland is in the middle of a divergent boundary. Iceland was formed when magma rose to the ocean surface to form an island. Iceland is the only place on Earth where you can see an ocean spreading center on land! Mr. Enns went to Iceland 4 years ago to check it out… Iceland North American plate Eurasian plate Thingvellir North American Plate Eurasian Plate Thingvellir 1. Divergent Boundaries Divergent boundaries can also occur on land. Continents split apart at divergent boundaries on land.. The Great Rift Valley in eastern Africa is a result of a continental divergent boundary. Here, the Arabian plate is moving away from the African plate over millions of years… African Rift Valley Eurasian plate Arabian plate African plate Great African Rift Valley Great African Rift Valley 2. Convergent Boundaries A convergent boundary is where 2 plates push together. At these boundaries, crust material is either folded or destroyed. When two plates collide, the density of the plates determines which plate comes out on top! Oceanic crust is more dense than continental crust. continental continental continental oceanic subduction crust is folded: mountains crust subducts: ocean trench Continental-Continental A continental-continental collision occurs when 2 continental plates push together. Both plates have the same density, so their edges crumple and fold. This forms mountain ranges, like the Himalayas. Here, the Indian plate is colliding with the Eurasian plate. Continental-Continental Eurasian plate Indian plate Eurasian plate Indian plate The Himalayas Oceanic-Continental A oceanic-continental collision occurs when an oceanic plate collides with a continental plate. Since the oceanic plate has a greater density, it sinks or subducts below. This forms ocean trenches, coastal mountains & volcanoes. The Cascade Mountains on the west coast are examples… Oceanic-Continental subduction zone Oceanic-Continental Juan de Fuca plate Pacific plate North American plate Juan de Fuca plate North American plate Pacific plate The Cascade Mountains 3. Transform Boundaries A transform boundary is where 2 plates scrape past each other in opposite directions. At these boundaries, crust material is neither created or destroyed. They exist mainly at midocean ridges, but also on land. The San Andreas Fault in California is an example… 3. Transform Boundaries Juan de Fuca plate Pacific plate North American plate Juan de Fuca plate North American plate Pacific plate The San Andreas Fault 1. Divergent Where two plates move apart. 2. Convergent Where two plates push together. 3. Transform Where two plates scrape by each other. Any Questions?
