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Transcript
Tectonic Hazards
Key Question=What are plate
boundaries and the resulting
hazards?
By the end of the lesson you will need to be able to: Name and the describe the layers of the earth
 Describe what a plate boundary is and how they
move around on the mantle.
 Identify the 2 types of crust and describe their
characteristics
Starter activity-what do you already know about the structure
of the earth?
What are tectonic plates?
Plate tectonics
The map below shows a map of the plate boundaries (where 2 plate
boundaries meet). The arrows show the direction of the plate
movement and give an indication as to the type of plate boundary.
https://www.youtube.com/watch?v=kwfNGatxUJI
Plate movement
How do the
earth’s tectonic
plates move?
https://www.youtube.com/watch?v=0mWQs
1_L3fA
The Earth's crust is broken up into pieces called plates. Heat
rising and falling inside the mantle creates convection
currents. The convection currents move the plates around
on the mantle.
Types of crust – oceanic and
continental
Oceanic crust:
As the name already suggests, this crust
is below the oceans. There, the crust is
4-7 miles (6-11 km) thick. The rocks of
the oceanic crust are very young
compared with the rocks of the
continental crust. The rocks of the
oceanic crust are not older than 200
million years.
Continental crust
The earth's crust is the thickest below the continents, with an average of
about 20 to 25 miles (30 to 40 km) and with a maximum of 45 miles (70
km). The continental crust is older than the oceanic crust, some rocks
are 3.8 billion years old. The continental crust mainly consists of igneous
1). Constructive plate
boundaries
•Here the land is moving apart
•It constructs new crust, e.g. Mid Atlantic
Ridge
•You may get earthquakes as friction is
caused as they move over the mantle.
•There is lots of volcanic activity from
fissures e.g. Iceland.
late Boundaries
2). Destructive subduction plate boundary
•Here oceanic and continental crust is
moving together.
•The oceanic crust is denser (heavier) and
therefore sinks (subducts) underneath
the continental crust.
This friction
causes earthquakes.
•The land on the edge of the continental plate gets squashed up and makes
FOLD MOUNTAINS e.g. the Andes.
•The oceanic crust melts as it is forced under the continental crust. Once
under it is still lighter than the mantle it has entered.
•It rises up through weaknesses in the crust and reaches the surface
explosively as a volcano
Here the plates
move apart,
magma moves up
from the mantle
below and makes
new land
Landform = mid-ocean ridge (Atlantic)
Constructive
boundary
Here the plates
move towards
each other.
Oceanic crust is
more dense and is
forced down
(subducted)
beneath the
lighter continental
crust. It melts into
the mantle
Landform = Ocean
Trench
Landform
= Volcano
Destructive
boundary
3). Conservative/transform plate boundaries
•Here the plates are moving past each other.
•There are many earthquakes along these
margins as friction builds up
•There are no volcanoes on a conservative
plate boundary.
•E.g, San Andreas Fault in California (North
American Plate & Pacific Plate)
late Boundaries
4). Destructive/Collision Zones
•Here 2 continental plates are
pushing into each other.
•They weigh the same so neither
of them sinks and they squash
upwards
to
make
FOLD
MOUNTAINS, e.g. Himalayas.
•There are strong earthquakes
at these margins because of the
huge pressures created.
CASE STUDY – Living in a collision zone – Pg12 & 13 – Himalayas (farming; mining;
Tourism & living with danger)
No landforms occur here but
lots of earthquakes happen
Landform = Fold
Mountain
Destructive collision zone
Here the plates move together. As they are both
continental they weight the same and force each other to
fold upwards creating fold mountain ranges.
Plenary-True or False-Whiteboard Work
1.
2.
3.
4.
5.
A plate boundary is where 2 plates meet.
The earth’s crust sits on the outer core.
The mantle is liquid rock.
There are 5 types of plate boundary.
An example of a constructive plate margin is
the Eurasian and North American plates.
6. Convection currents move the plates around.
7. Conservative plate margins form new land.
8. There are 3 types of crust.
9. Destructive collision zones happen when the
2 pieces of crust are different densities.
10. Ocean trenches form at subduction zones.
Plenary-True or False-Whiteboard Work
1.
2.
3.
4.
5.
A plate boundary is where 2 plates meet.
The earth’s crust sits on the outer core.
The mantle is liquid rock.
There are 5 types of plate boundary.
An example of a constructive plate margin is
the Eurasian and North American plates.
6. Convection currents move the plates around.
7. Conservative plate margins form new land.
8. There are 3 types of crust.
9. Destructive collision zones happen when the
2 pieces of crust are different densities.
10. Ocean trenches form at subduction zones.
Now correct the inaccuracies in the red ones…….What should they say?
Homework
-CGP Exam practice work booklet
Pg3 Tectonic Plates
Plate boundaries
A plate boundary is
are made from the earth’s crust.
characteristics….
.
Plates
There are 2 different types of crust. The table below shows the types and their
There are 3 types of plate boundary……….
1). Destructive-subduction
A global example is
1). Destructive-collision A global example is
2). Constructive
A global example is
3). Conservative
A global example is
Plate boundaries
Type of
plate
Destructive
subduction
Direction
of
movement
Towards each
other and then
forced down
Type of
crust
Oceanic forced
under
continental
Global
example
Nazca Plate
under the South
American Plate
Hazard/
landform
Ocean Trench
Fold Mountain
Volcano
Earthquake.
Destructive
Collision
Conservative
Constructive