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Copy of Tectonic plate boundaries part 1
Transcript of Copy of Tectonic plate boundaries part 1
Tectonic plate Boundaries part 1 Convergent plate boundaries Convergent plate boundaries occurs when tectonic plates meet and collide. (converge = to meet)
Lithospheric plates colliding are called converging plates.
Converging plates form a deep underwater valley called a trench.
The effects of these collisions include earthquakes, volcanic activity and crustal deformation. 3 types of converging plates Oceanic - continental plate convergence Oceanic - continental plate convergence occurs when thinner, more dense oceanic (in water) plate is overridden by a thicker, less dense continental (land) plate.
Oceanic plate is forced down into the mantle. - in a process called "subduction".
The subducting plate descends and approaches melting temperature (100 miles = 160 km).
Partial melting of ocean crust and mantle produce magma chambers.
Some magma cool and crystallizes into large rock masses below surface of continental plate. But can also asscent through overlying materials , melting and fracturing their way upwards.
This results to formation of a long chain of volcanoes ( volcanic belt ) and continental rocks crumpling and folding ( mountain ranges )
The mid- ocean ridge consists of one continuous mountain range with four prominent branching ranges, it has a continuous length of 40, 400 mi ( 65, 000 km ) Juan de Fuca plate and
North American plate British Columbia's Coast Mountain
and Cascade Mountain Range Oceanic - oceanic plate convergence Oceanic - oceanic plate convergence occurs when a higher density oceanic plate ( caused by cooling) subducts.
The subducting plate descends deeper, heats and melts.
Melting magma reaches the surface and forms volcano islands.
These volcanoes start deep beneath the ocean surface but grows higher in sea level.
A long chain of volcanic islands is called a "volcanic island arc".
An area where magma rises to Earth's surface is called a hot spot.
These hot spots can penetrate volcanic activity and can appear as chains, such as island chains. As the overlying plate moves one volcano off the hot spot, another is formed. Continental - continental plate convergence It is a powerful collision between thick, massive rocky plates.
Subduction is prevented because the plates have higher density than the mantle, but a small amount of subduction and the destruction of lithospheric crust can also occur.
The compression (of plates) causes crumpling and folding, pushing the plate upwards, forming great mountain ranges.
An example : The Himalayas formed by the Indian and Asian continent colliding, 40 - 50 millions years ago. These mountain ranges are still growing ! By:
Michal, Jimmie and Eva :) JAPAN! The Himalayas
NOTES: Pay attention! QUIZ AFTER THE PRESENTATION!
take notes! THE END QUIZ TIME! QUIZ TIME! An example of a hot spot chain:
The Hawaiian Islands