Structure And Plates

The Earth is like an Apple!

CRUST

(where we live)

MANTLE

CORE

The Structure of the Earth

CRUST MANTLE

CORE

•Inner

•Outer

The 2 different types of The 2 different types of plateplate

CONTINENTAL OCEANIC

- 25-100km thick- Light (and so does not sink)- Not destroyed as easily as oceanic crust

- 5-10KM thick- Dense- Constantly being renewed and destroyed

Convection Currents

Mantle

Crust

Plates move due to Plates move due to convection currentsconvection currents

The hot magma rises from above the coreThe hot magma rises from above the core As it cools, it sinks and then moves As it cools, it sinks and then moves

downwards towards the core again.downwards towards the core again. This causes the plates to move apartThis causes the plates to move apart

Plate Names

African Plate

Indo Australian Plate

North American

South American

Eurasian

Pacific

Nazca

Antarctic

Evidence for plate tectonics

1. Study of fossils – similar fossils are found on differentcontinents. This is evidence that these regions were once very close or joined together.

3. Shape of continents fit together like a jigsaw.

Africa

SouthAmerica

2. Pattern of rocks – similar pattern of rock layers on different continents is evidence that the rocks were once close together or joined.

What are plate margins?What are plate margins?

This is where 2 or more plates meet. This is where 2 or more plates meet. There are 3 different types of plate There are 3 different types of plate

movement;movement; Away from each other (Constructive – as Away from each other (Constructive – as

new crust is constructed)new crust is constructed) Towards each other (Destructive – as crust Towards each other (Destructive – as crust

is being destroyed). This category can be is being destroyed). This category can be sub divided into subduction and sub divided into subduction and destructive destructive

Sliding past each other (Conservative) Sliding past each other (Conservative)

A destructive plate boundary is found where a continental plate meets an oceanic plate.

The oceanic plate descends under the continental plate because it is denser. As the plate descends it starts to melt due to the friction caused by the movement between the plates. This melted plate is now hot, liquid rock (magma). The magma rises through the gaps in the continental plate. If it reaches the surface, the liquid rock forms a volcano.

1) Destructive Plate Boundary

a) Subduction

Collision boundaries occur when 2 plates of similar densities move together (i.e. a continental plate and a continental plate). This causes the material between them to buckle and rise up, forming fold mountains.

The Himalayas are an example of a chain of fold mountains. They have been formed by the African plate colliding into the Eurasian plate.

1) Destructive cont.

b) Collision Boundary

Conservative plate boundaries exist where two plates do not directly collide but slide past each other along a fault (weakness).

No volcanoes are found along these plate boundaries, but earthquakes do occur.

An example of such a boundary is the San Andreas Fault in California.

2) Conservative Boundary

3) Constructive Plate BoundaryAt a constructive plate boundary, two plates move apart. As the two plates move apart, magma rises up to fill the gap. This causes volcanoes at this type of boundary. However, since the magma can escape easily at the surface the volcano does not erupt with much force. Earthquakes are also found at constructive boundaries.

An example of a constructive boundary is the Mid-Atlantic Ridge.

Sea Floor Spreading!

Did you know that the ocean floor in the Atlantic is growing by 3cm per year?

Which of the following pairs of continents are moving further away from each other?

1) Europe and Africa

2) Europe and North America

3) South America and North America

Mid-Atlantic ridge

Name this plate boundary

Continental crust

Mantle

The oceanic crust melts and rises

Explosive volcanoes

Oceanic plate

The oceanic crust sinks under the less dense continental crust

Earthquakes occur due to friction

Match the labels to the letters

A B

C D

E

F

G

Constructive plate boundaries

Ocean

Oceanic Crust

Mantle

MID OCEAN RIDGE

Where would you find older rocks – at A or at B?

AB