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9 Cards in this Set
- Front
- Back
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Why plate boundaries occur |
The earth is made up of 3 layers, the core, mantle and crust. The crust is broken up into many pieces known as plates. Due to radioactive decay in the core, high amts of heat is emitted, melting the ranks in the mantle. The melted rock expands, becomes less dense and rise to the crust, forming convectional currents. When the rising convention currents diverge and spreads out beneath the crust, it drags the 2 plates apart, forming a divergent plate boundary. When the semi molten rocks cools, becomes denser, sinks and converges, the conventional currents cse the plate to move towards each other, resulting in a convergent plate boundary. |
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Slab pull force |
At the subduction boundary, one plate is denser and heavier than the other. The denser oceanic plate subducts under the less dense plate, pulling the rest of the plate along with it. The force of the sinking plate exerts on the rest of the plate is the slab pull force. The slab pull force speeds up the divergent at the convergent plate boundary. The slab pull force at the divergent plate boundary may cause earthquakes due to the friction |
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Type of plate boundary |
Convergent-CC, OC,OO Divergent-CC,OO Tranform-CC |
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Convergent-OC |
When 1 oceanic and 1 continental plate converge, the 2 plates collide and push against each other. The denser oceanic plate subducts under the less dense continental plate. When subduction takes place, the subducted oceanic plate causes the mantle above it to melt, forming magma. Magma rises through the crust of the continental plate to form volcanoes. Compression pushes the softer rocks on the continental plate to fold and buckle to form fold mountains. The Nazca plate subducts under the south American plate to form the Chile-Peruvian trench in the ocean and the Andes fold mountains on the continental crust.
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Convergent-CC |
When 2 continental plates converge, the two plates collide and push against each other. As the continental plates are thick and buoyant, no subduction takes place. The compression causes layers of rocks along the boundary to buckle and fold. This causes fold mountains to form. An example of fold mountains is the Eurasian and Indian plate converging forming the Himalayas. |
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Convergent-OO |
When 2 oceanic plate converges, the 2 plates will collide and push against each other. The denser oceanic plate will subduct under the less dense oceanic plate. When subduction occurs, the subducted oceanic plate causes the mantle material to melt. The magma rises through the crust and forms undersea volcanoes. At the point of subduction, an oceanic trench is formed. The magma builds up and rises above sea level and gradually forms a volcanic island. The pacific plate subducts under the Philippine plate, forming the Mariana Trench and the Mariana islands. |
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Divergent-CC |
When 2 continental plate diverge, they move apart to form fractures. As the land continue to be pulls apart, the land between the fractures will sink forming a depression known as a rift valley. At various points of the rift valley, magma flows out and builds up and solidifies to form a rift volcano. An example is the Nubian boundary of the African plate moving away from the Somalian boundary of the African plate forming the East African rift system. |
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Divergent-OO |
When 2 oceanic plate diverge, magma rises from the mantle to form new sea floor. The magma flows onto the sea floor, cools and solidifies. This process is called sea floor spreading. This causes a mid-oceanic ridge to form. An example is the mid-Atlantic ridge in the middle of the Atlantic Ocean. It is formed when the North American and Eurasian plate moving away from each other. |
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Transform plate movement |
When 2 continental plate slide past each other, there is a lateral movement. The movement creates tremendous stress and builds up over time. When released, earthquakes are formed. One transform plate boundary is the San Andes fault between the pacific plate and American plate. |
