1.1.1 The Earth has four main layers – the inner
core, the outer core, the mantle and the
1.1.2 The inner core is 5,500°C -
extremely hot. It is a very dense
solid made from iron and nickel.
1.1.3 The outer core is 2,000 km
thick and is a liquid.
1.1.4 The mantle is semi-molten
and about 3,000 km thick.
1.1.5 The crust is the rocky outer
layer.The crust is made up of pieces
called plates. There are two types of
crust: oceanic and continental crust.
The oceanic crust is found under the
sea and is thinner and less dense
than the continental crust.
1.2 Plate Movement
1.2.1 Earthquakes and volcanoes are primarily found
at plate boundaries. Convection currents in the
mantle drive them to move. The mantle is much
hotter than the crust and its rock is molten. At
the boundaries between plates, molten magma
is able to force its way to the surface and
escape as lava.
2 What happens to the crust at plate boundaries?
2.1 Heat from the core causes convection
currents in the mantle. These currents
slowly move the crust around. In some
places the crust is destroyed. In other
places new crust is formed.
3 The effects of earthquakes on people
3.1 3 million people affected.
3.2 Over 220,000 deaths.
3.3 300,000 injured.
3.4 1.3 million made homeless.
3.5 Several hospitals
3.6 30,000 commercial
3.7 Businesses destroyed.
3.8 Damage to the main
3.9 Airport and port damaged.
4.1 Large earthquakes are usually connected
with plate boundaries. Earthquakes happen
often but most are too small for us to
notice. Seismometers record earth
4.2 An earthquake is a sudden shockwave caused by rocks
being under stress from the movements of plates at plate
boundaries, and this stress builds up until it reaches breaking
point, and all the energy stored up is released in the form of
4.3 In the past, the Richter scale was used to
measure the power of earthquakes.
Earthquakes are now measured using the
Moment Magnitude Scale which measures
the size of the seismic waves during the
earthquake. Each step in the scale is ten
times greater than the previous number.
4.4 The Mercalli Scale measures the damage caused
by an earthquake, the intensity, and changes
according to which area you are measuring.
5.1 A volcano is an opening in the Earth’s crust. It
allows hot magma, ash and gases to escape
from below the surface.
5.2 Composite Volcanoes
5.2.1 Steep-sided and cone-shaped, made up of layers
of ash and lava and containing sticky lava which
doesn’t flow very far.
5.2.2 Mount Etna in Italy is a composite volcano.
5.3 Shield Volcanoes
5.3.1 Have gently sloping sides and runny lava that covers a wide
area. Gases escape very easily from shield volcanoes.