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/