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JC Geography
JC Geography

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JC Geography

Plate tectonics.

2 types of plates.

Continental plates - under land.

Oceanic plates - under ocean.

3 types of plate movements

Separating plates - drag apart.

Colliding plates - pushed together

Sliding plates - slide past each other.

Separating plates.

As the two plates separate, magma rises up through the gaps.It then cools down becomes solid and forms new crust. Example - the Mid Atlantic Ridge.

Colliding plates

When plates collide , the crust is destroyed.When oceanic plates ( heavier) and a continental plate ( lighter) collide , the heavier oceanic plates is forced down into the hot mantle below and melts... (More)

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Volcanoes

  1. Plates separate or collide and magma rises up through a gap called a vent.
  2. The magma reaches the surface cools and hardens . This is called lava.
  3. After many eruptions  many layers of lava creates  a cones shaped mountain. 
  4. The top of the volcano where lava flows out is called the crater.

Types of volcano. 

Active - erupted  in the past 10,000 years ( Mt .Helen's USA).

Dormant - has not erupted in the past 10,000 years but may erupt again ( kilimanjaro Tanzia).

Extinct - never expected to erupt again.(Mount Kenya, Kenya).

 

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Dynamic earth

Plates: large slabs of earth's crust 

Plate boundaries: where plates meet

Crust: thin, solid layer all over the surface of the earth.

Mantle: thick layer of molten and semi-molten rock beneath the earth's surface.

Outer core: made of molten, nickel and iron.

Inner core: at the centre of the earth.

 

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Explain how convection currents cause tectonic plates to move.

1. The earth's core heats the magma above. As a result, the magma rises slowly upwards towards the crust.

2.  As the magma rises it then begins to cool. Subsequently, this cooling results in the magma becoming heavier and sinking back down towards the core.

3. This cycle continuously repeats and forms a circular movement of magma within the mantle. This causes, in these convection currents to move very slowly so plates are either dragged apart (separate), pushed together (collide) or slide past each other.