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Plate Tectonics IGCSE Geography
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PLATE TECTONICSIGCSE GRADE 10 GEOGRAPHY
REVISION
The Natural EnvironmentGeography
Earth’s Structure
Crust Continental Plate
Forms land, lighter than the oceanic plate (granite)
Oceanic Plate Below ocean, dense
heavy rock (basalt) Mantle Outer Core Inner Core
The Earth is made up of the inner and outer core, the mantle and the crust.
There are two types of plates. The continental and the oceanic plate. The continental plate is mostly above the ocean, forming land. It is between 25 and 100 kilometers and is mostly made of granite, a lighter rock than basalt. The oceanic plate is mostly below the ocean. It is mainly made of basalt between 5 and 10 kilometers thick. Basalt is a denser and heavier rock and sinks below the continental plate.
The Convection Currents
Around the solid core of the earth is a layer of molten magma called the mantle. Convection currents flow through this layer which move plates floating on the mantle.
The Earth’s Tectonic Plates
Nazca Plate South
American Plate
African Plate
Pacific Plate
North American Plate
Eurasian Plate
Antarctic Plate
Indo-Australian Plate
Plate Boundaries
3 Types of Plate Boundaries Constructive
Divergent plate margin
Destructive Convergent plate margin Collision plate margin
Conservative plate margin
Constructive boundary:
Plates move apart Volcanoes formed
as magma wells up to fill the gap
New Crust made In oceans,
oceanic ridges are formed
Ex: Mid-Atlantic ridge
Constructive plate boundaries. They occur when two plate boundaries move apart. The magma wells up the gap and forms new crust, this forms volcanoes.
Destructive boundary: Convergent
Oceanic and continental plates move together
Oceanic plate forced under continental plate
Friction: earthquakes and melting of the plate
Magma rises up through cracks breaks onto surface
Ex: boundary between Nazca and South American Plates
Convergent destructive boundary. This occurs when oceanic and continental plates move together. As the oceanic plate is forced under the lighter continental plate, friction causes the melting of the oceanic plate and earthquakes. Magma rises us through the cracks onto the surface to form volcanoes.
Collisional boundary:
2 continental plates
Neither plate is forced under the other
Therefore, both are forced up
Fold-mountains formed
Ex: Himalayas
Collisional destructive boundary. When two continental plates collide, neither of them is forced down and therefore are both forced up to form fold-mountains.
Conservative boundary:
When plates move past each other in opposite direction
Friction is eventually overcome and the plates slip past each other in a sudden movement
This causes an earthquake
Ex: San Andreas Fault, California
Conservative boundary. When plates move past each other in opposite direction or a different speeds, tension is built up in the rocks and released in an earthquake when the friction is overcome.
Earthquakes
Seismometers record earth movements An Earthquakes is a sudden shockwave
(a rapid flow of energy) caused by rocks under stress due to the movement of the earth’s plates
The Richter scale is used to measure the strength of earthquakes
Example: Earthquake in Haiti: Case Study in Notes for further information
Volcanoes
A volcano is an opening in the earth’s crust allowing magma, ash and gases from the mantle to reach the surface
2 types of volcanoes Composite Shield
Tsunamis
A tsunami is a sea wave caused by the displacement of large quantities of water
Can be caused by earthquakes trigged by the movement of the crust under the ocean
Bibliography
http://www.bbc.co.uk/bitesize/ks3/geography/physical_processes/plate_tectonics/revision/1/