Transcript earthquake - St Hugh`s School

Earthquakes
and Plate
Tectonics
In this unit we will be
learning about the
structure of the earth,
Plate tectonics and the
cause and impact of
earthquakes and volcanoes
Structure of the Earth
Convection currents in the
mantle..
On the map locate and name the following earthquakes
NewZealand 2010
Haiti 2010
Japan 2011
Turkey 2011
Highlight a conservative, a constructive and a destructive plate margin (provide a key)
Earthquakes
Earthquakes are caused by the release of built-up pressure inside the
Earth's crust.
An earthquake's power is measured on the Richter scale using an
instrument called a 'seismometer'.
The effects of an earthquake can be devastating - they can destroy
settlements, change landscapes, and cause many deaths.
Causes
An earthquake is the shaking and vibration of the Earth's crust due to
movement of the Earth's plates (plate tectonics). Earthquakes can
happen along any type of plate boundary.
Earthquakes occur when tension is released from inside the crust.
Plates do not always move smoothly alongside each other and
sometimes get stuck. When this happens pressure builds up. When this
pressure is eventually released, an earthquake tends to occur.
DESTRUCTIVE (converging) PLATE BOUNDARIES
• Oceanic and continental Plates collide
• Heavier Oceanic plate sinks under the continental one into
what is known as a SUBDUCTION ZONE
• When plates rub, friction occurs, leading to earthquakes
• Pacific Ring of Fire is most famous destructive plate
boundary.
Collision boundary (converging)
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Two continental plates push together
Neither sinks as they are made from light rock
Plates buckle to form fold mountains ( Himalayas)
No volcanoes but violent earthquakes
CONSTRUCTIVE (diverging) PLATE BOUNDARY
•
•
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Two plates move apart
Magma rises to the surface
Volcanoes are formed
Mostly beneath the sea forming chains of volcanoes eg Mid
Atlantic Ridge
CONSERVATIVE PLATE BOUNDARY
• Tectonic plates slide
past each other
• Plates become
locked and tension
builds up over years
• Rocks break and
jerk forward causing
powerful
earthquakes
• Eg San Andreas
Fault
Earthquakes
• The point inside the crust where the pressure is released is
called the focus. The point on the Earth's surface above the
focus is called the epicentre.
• Earthquake energy is released in seismic waves. These waves
spread out from the focus. The waves are felt most strongly at
the epicentre, becoming less strong as they travel further away.
The most severe damage caused by an earthquake will happen
close to the epicentre.Measured on the richter scale from 1-10
Effects of an earthquake
Earthquakes can destroy settlements and kill many
people. Aftershocks can cause even more damage to an
area. It is possible to classify the impacts of an
earthquake, by taking the following factors into account:
• social impacts (the impact on people)
• economic impacts (the impact on the wealth of an
area)
• environmental impacts (the impact on the landscape
These may be grouped into short term or long term
effects.
•
Seehttp://www.bbc.co.uk/schools/gcsebitesize/geography/natural_hazards/earthquakes_rev3.shtml
Impact of Earthquakes
The overall impact will depend on the size of the
earthquake and the development of the country.
An L.E.D.C ( L_____. E_____. D_____.C______)
will suffer more due to poor building
construction and infrastructure and inadequate
warning sysems or emergency services.
• List examples of the following…..
• Short term effects of earthquakes
• Long term effects of earthquakes and natural
disasters
DEFINITIONS
Tectonic Plates – huge slabs of rock which form the Earth’s crust
and which float on the mantle; the lightest and thickest plates are
called CONTINENTAL CRUST and form land ; the thinner but
heavier crust is called OCEANIC CRUST and has sea over it.
What is the Ring of Fire?
The name given to the
destructive plate boundary
which forms a and of
earthquakes and volcanoes
round the edge of the Pacific
Ocean.