Stage 1 Magma rises to the crust within the mantle This creates friction and causes the plates to move What are the 3 main ways plates move 1 2 3 Stage 2 Pressure builds between plates and sometimes small earthquakes are felt ID: 645046
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Slide1
Extreme Natural Events
Earthquake processes. Slide2
Stage 1.
Magma rises to the crust within the mantle. This creates friction and causes the plates to move.
What are the 3 main ways plates move
1.
2.
3. Slide3
Stage 2
Pressure builds between plates and sometimes small earthquakes are felt.
Sudden rupture of the plates along a fault line happens, and the earth shakes for 15-40 seconds.
The centre point of the rupture inside the earth is called the
focus
. Seismic waves radiate in all directions from the focus. The centre point on the earths surface above the focus is called the
epicentre.Slide4
Stage 2: waves
P waves
(primary): first felt, does little damage.
S waves
(secondary): arrives shortly after P wave. I makes the ground shake vertically (up & down) and horizontally (side to side) like jelly. These can be very damaging.
L waves
(long wave): arrives last, like water rippling, it moves the ground sideways and can be very damaging.Slide5
Recap
An
earthquake focus
is where earthquakes start. Energy is release when rocks suddenly snap
The
epicentre
is on the surface, directly above the focus.
A
seismograph
is an instrument that detects earthquake waves and records them on a graph called
a seismograph. Slide6
Stage 3
The earthquake can damage land and buildings, phone lines can be down and mobile networks overloaded.
First response, save as many people as possible.Slide7
Stage 4: aftershocks
Can be felt days, weeks, months afterwards, they can be large and destructive. Slide8
Recovery
State of emergency may be declared by Civil Defence. Immediate concerns are the injured, food, shelter for survivors.
Unsafe areas are evacuated, schools, halls and
maraes
are used as shelter centres. Slide9
Stage 6: rehabilitation
The rebuilding of buildings, roads, services and economic facilities may take months and is very costly. Slide10
Sequence of events
Stress in tectonic plates
Foreshocks shocks may happen before the big one
Earthquake happens
Shaking is felt once waves surface
Shaking lasts few seconds or several min.
Aftershocks occur
Process starts againSlide11
Earthquake processes
Create a flow chart in your books, using these phrases put them in their correct order.
Stress causes rupture at the plate boundaries
Seismic waves radiate out from the earthquakes focus.
Ongoing
global plate movement
The earthquake is felt by people as the seismic waves surfaces.
Stress builds up in rocks at plate boundaries
Movement along a fault line or the creation of a new fault line *(4)
The point on the earths surface reached first by the seismic waves is the epicentre. *(6)