Download What happens at the different plate boundaries?

Learning objectives
• What happens at the different plate
boundaries?
• We will learn that different events happen
along the different plate edges or plate
boundaries.
Cross section of the Earth
Cross section of the Earth
Continental drift
What is plate tectonics?
What is Plate Tectonics?
. The Earth's surface is made up of a number of large plates (like
pieces of a jigsaw puzzle) that are in constant, slow motion.
The ocean floors are continually moving, spreading from the centre
and sinking at the edges.
At the edges of these plates (plate boundaries) earthquakes and
volcanoes occur.
Convection currents in the mantle move the plates. The source of
heat driving the convection currents is radioactive decay which is
happening deep in the Earth.
Why do the plates move?
Plate names
North
American
Eurasian
Pacific
Pacific
African
Nazca
South
American
Indo-Australian
Plate
Antarctic
Plate names
Constructive plate boundary
At a constructive plate boundary, two plates move apart.
As the two plates move apart, magma rises up to fill the
gap. This causes volcanoes.
Earthquakes are also found at constructive boundaries.
An example of a constructive boundary is the Mid-Atlantic
Ridge.
Constructive plate boundary
How fast do plates move?
Tectonic plates move at different rates.
The Nazca and Pacific plates are moving apart at a rate of
18cm per year while the Eurasian and North American
plates are moving apart at a rate of 3cm per year.
To the nearest metre, how far will the Nazca and Pacific
plates have moved over the next 200 years?
6 metres
36 metres
200 metres
928 metres
Constructive plate boundaries
mid-ocean ridge
B
A
ocean
mantle
Where would you find older rocks – at A or at B?
Destructive plate boundary
A destructive plate boundary is found where a
continental plate meets an oceanic plate.
The oceanic plate moves under the continental plate
because it is heavier. As the plate moves under it starts to
melt because of the friction caused by them rubbing
together. 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.
Destructive plate boundary
Collision plate boundary
Collision boundaries happen when two plates of similar
weight move together (i.e. two continental plates). 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.
Collision plate boundary
Conservative plate boundary
Conservative plate boundaries happen where two plates
do not directly hit in to eachother 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.
Conservative plate boundary
Plate definitions