tectonic plates

Explain oceanic plate

Thinner, denser

Explain continental plate

Less dense, thicker

Why do plates move?

Due to convection currents in the asthenosphere

How are convection currents caused?

Convection currents are caused when less dense magma rises and cools and then sinks

What are the three different plate boundaries

Destructive, constructive, conservative

Explain destructive

Plates move towards each other

Explain constructive

Plates move away from each other

Explain conservative

Plates move parallel each other either in same direction or different direction at different speeds

Explain O+O in constructive plate boundary

Magma rises in between the gap left by the separated plates

• new land forms when the magma cools

• E.g. Mid Atlantic Ridge

Explain C+C in constructive plate

Any land in the separated gap is forced apart due to plates moving apart

• Creates a rift valley (East African rift valley)

• Volcanoes formed when magma rises

• Eventually gap will fill with water and separate

Explain conservative in detail

Plates moving parallel to each other in different direction/speed

• e.g. San Andreas fault

• Powerful earthquakes as plates can stick together and build up lots of pressure

Explain C/O in destructive plates

1. Denser O plate is subducted under C plate

2. Plate subducting leaves a deep ocean trench (Peru-Chile trench)

3. Melting of the subducting plate forms explosive composite volcanoes on the C plate (andesitic and rhyolitic flows)

4. Also forms fold mountains where the C plate is compressed and folded (The Andes)

Explain O/O in destructive plates

1. Denser/older plate will subduct causing deep sea ocean trenches to form such as Mariana

2. Built up pressure causes underwater volcanoes

3. Lava cools and makes new land called island arcs

Explain C/C in destructive plates

1. Have similar density so no subduction

2. Land is forced upwards

3. Fold mountains e.g. Himalayas

Explain slab pull

Plate subducts into the mantle and plate sinking pulls the rest of the plate due to gravity

Explain ridge push

When magma rises, plates forced to move apart. Slope created has gravity acting upon it as it is a higher elevation and is forced to move downhill due to gravity. Gap is widened over time.