Download 1.2 Sudden Earth Events (earthquakes or volcanoes)

1.2 Sudden Earth
Events (earthquakes
or volcanoes)
Earthquakes
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Trembling or vibrations of the ground, caused
by the sudden release of energy that has slowly
been building up in Earth’s crust.
Large masses of rock in the crust move and
sometimes become locked together or stuck.
A tremendous force is created until finally the
rocks break.
This sudden break causes an earthquake.
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There are 3 types of seismic waves that
occur in an earthquake.
1) Primary (P-waves) – these are the
fastest of the 3 waves and arrive first on
Earth’s surface to warn people in
earthquake areas.
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2) Secondary (S-waves) – travel more
slowly than P-waves and can pass only
through solids, not liquids or gases.
3) Surface Waves – are the slowest, but
their rolling motion breaks up roads and
buildings, so they do the most damage.
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Focus – first place that the rock breaks
below the surface in an earthquake
Seismic Waves – shock waves caused by
an earthquake.
Epicentre – point on the surface directly
above the focus
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When P & S-waves reach the epicenter
they generate the surface waves which
travel outward like water ripples from a
stone being tossed into water.
Example
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Water displaced by an earthquake is called
a tsunamis (huge waves).
Liquefaction is the process of changing into
a liquid-like substance such as quicksand.
The sandy base is turned into quicksand,
and many buildings fall over.
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Richter Scale – scale developed by
Charles Richter that measures the
magnitude of an earthquake. Scale starts at
0, and each increase of 1 means an
increase of 10 times the amount of ground
motion.
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Generally earthquakes of 2 or less are not felt.
Magnitudes of 5.0-5.9 create damaging shocks.
6.0-6.9 are destructive in populated regions.
Approximately 18 earthquakes per year are
considered major: 7.0 – 7.9.
Magnitudes higher than 8.0 produce total
destruction to communities.
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Volcano – an opening in Earth’s crust
through which solid and molten rock, ash,
and gases escape.
Pg 360 – diagram of a volcano
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When volcanoes are not active they are
described as dormant.
Ring of fire is an area of volcanoes around
the Pacific ocean
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Lava – molten rock that flows out of a
volcano.
Ash – fine, burnt particles from a volcanic
eruption.
Magma – molten rock inside Earth.
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Seismograph – device that detects the
waves of energy that spread through the
earth from the focus of an earthquake.
Surveyor’s Level – device that measure
minute changes in the angle of the
ground’s slope.
Seismogram – print out of seismograph
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The earliest
seismograph
was invented in
China A.D. 136
by a man named
Choko.
Historic Canadian Earthquakes
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Volcanoes
Oh My God
seismic seconds