Tectonic Landforms

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Divergent 1

Continental - Continental 

1) Plate move apart form each other and when magma rises a bulge forms

2) Continuous movement apart from plates provide pressure to the bulge causing it to sink and flatten

3) The plate carries on moving and rifting and faults occur forming a sunken valley known as graben.

4) As rifting continues to stretch graben more faults occure so magme can well up through the cracks forming volcanoes.

Example - East African Rift Valley

- Extends 3000km from Ethiopia to Mozambique

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Divergent 2

Oceanic - Oceanic 

1) Plates move apart due to convection currents in the mantle

2) Magma rises up through the gaps and cools and condenses forming an ocean ridge

3) The magma rising isnt continuous as there are instabilities in the crust which cause transform faults to occur at right angles

4) No volcanic activity occurs at the transform faults but earthquakes can occur

Example - Mid Atlantic Ridge

- 60,000 km in length 

- 3,000m above sea bed

- Between North American and Eurasian Plates 

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Convergent 1

Oceanic - Continental

1) The two plates move towards each other and the denser oceanic plate subducts under the continental plate at the Benioff Zone at a 45 degree angle.

2) Subducting also causes faulting to occur and the energy released in the process causes earthquakes.

3) As the plate descends it starts to get heated up and melt.

4) The less dense melted plate rises to the surface known as plutons and can cause volcanoes

5) The ocean trench formed is a long narrow deep depression.

Example - Marianas Trench 

- 200km long 

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Convergent 2

Oceanic - Oceanic

1) Two oceanic plates converge and the denser of the two subducts under the other creating a trench.

2) As the descending plate starts to melt due to heat in the mantle the melted material rises to the surface and forms the chain of volcanic islands.

3) The voclanic islands form parallel to the ocean trenches in the subduction zone.

Example - Atilles

- In Central America as the North American plate subducts under the Caribbean plate.

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Convergent 3

Continental - Continental

1) Both continental plates converge and as they have similar densities neither subduct so both plates are forced together 

2) The crust crumples and fols upwards (orographic lift) forming fold mountains.

Example - Himilayas 

- Formed between the Indo-Australian and Eurasian Plate

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Conservative

1) Plates move at different speeds parallel to each other in the same or opposite directions.

2) Friction resistance due to the movement occurs and causes a build up of pressue over time.

3) Eventually a sudden movement occurs and the pressure is released in the form of seismic waves which cause an earthquake to occur

Example - Haiti 2010 Earthquake

- The North American and Caribbean plate slid past eachother creating this earthquake

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Hot Spot Volcanoes

1) Occurs when a concentrated radioactive area creates a mantle plume under the tectonic plate

2) The mantle plume starts to heat the upper mantle and lithosphere and eventually it will start to melt and magma becomes less dense and starts to rise up.

3) Once magma rises it forms an underwater volcano which overtime more basaltic magma accumulates allowing the voclano to build up and rise to the surface forming an island volcano.

4) Due to convenction currents in the mantle the plate moves but the mantle plume hotspot remains in its original position.

5) Therefore as the plate moves the volcano moves with it so the volcano loses its source of magma and becomes extinct.

6) On the new area above the hotspot the whole process occurs again and another volcano forms. This cycle happens over millions of years and forms a chain of hotspot volcanoes

7) Overtime the older volcanoes start to become eroded due to geomorphic processes like weathering causing them to become sea mountains.

Example - Hawaii

-Oldest one is calle Kauai and is 3.8m years old

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