Plate Tectonics IGCSE Geography

1. PLATE TECTONICS
IGCSE GRADE 10 GEOGRAPHY REVISION
The Natural Environment
Geography

2. 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

3.  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.

4. 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.

5. The Earth’s Tectonic Plates
Nazca Plate
South
American Plate
African Plate
Pacific Plate
North American
Plate
Eurasian Plate
Antarctic Plate
Indo-Australian Plate

6. Plate Boundaries
 3 Types of Plate Boundaries
 Constructive
 Divergent plate margin
 Destructive
 Convergent plate margin
 Collision plate margin
 Conservative plate margin

7. 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.

8. 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.

9. 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.

10. 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

11. 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

12. 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

13. 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

14. Bibliography
 http://www.bbc.co.uk/bitesize/ks3/geo
graphy/physical_processes/plate_tecto
nics/revision/1/