66831
World at Risk 2
- Hazard distribution
- Geophysical
hazards usually
occur near plate
boundaries
- Earths crust made up of huge
plates called tectonics
- Two types
- thicker (less dense)
is the continental crust
- Thinner (more
dense) is the
oceanic crust
- thicker (less dense)
is the continental crust
- Plates move because of
convection currents in the
mantle these are caused
by temperature
differences within the
mantle
- Earths crust made up of huge
plates called tectonics
- Volcanoes and
earthquakes occur
at constructive
boundaries
- Constructive- 2 plates
move apart
- Mantle is under
pressure from plates
above
- when they move
pressure is released this
causes mantle to melt
and produce magma
- Magma is less dense
than the plate above so it
rises and erupts
- Constructive- 2 plates
move apart
- Volcanoes and
earthquakes also
occur at destructive
boundaries
- Destructive- when 2
plates move towards
each other
- Continental and oceanic
crust move towards each
other more dense oceanic
is forced under the
continental plate.
- Oceanic is heated
b friction and
contact with the
upper mantle which
melts the magma
- magma is less dense than
the continental crust and
will rise back to the surface
to form a volcano
- Destructive- when 2
plates move towards
each other
- Earthquakes also occur
at conservative
boundaries
- conservative- when 2
plates are moving apart
- 2 plates get locked
together in places and
pressure builds up
- Causes plates to jerk
past each other releasing
the energy as an
earthquake
- conservative- when 2
plates are moving apart
- Tropical
cyclones occur
over warm
water
- develop above water
26.5C or higher Moist air
rises and condenses it
releases energy which
increases wind speed
- loses strength
when over land
because energy
supply is cut off
- occur between 5 and
30 north and south of
the equator
- Cyclones spin because of the
Coriolis effect force that deflects the
path of winds due to the earths
rotation
- This is why they move away
from the equator
- This is why they move away
from the equator
- develop above water
26.5C or higher Moist air
rises and condenses it
releases energy which
increases wind speed
- Volcanoes also occur away
from plate boundaries
- These volcanoes are thought to be
caused by magma rising from large
chamber beneath the crust
- These volcanoes are thought to be
caused by magma rising from large
chamber beneath the crust
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