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Earth Science Ch. 11: Earthquakes and Volcanoes
Ch. 11-1: Earthquakes Key Terms
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Ch. 11-1: Why Do I Need To Know This?
•Because
rock!
•Because earthquakes are a major geological
•Because you need to be
in California.
for a major earthquake.
Earthquakes
•An
is the
and trembling that
results from the sudden movement of part of the Earth’s
.
•Over
earthquakes happen every year (about 1 every
seconds).
•Most are so small that we
feel them.
•Earthquakes happen along
, or big cracks in the surface of the
earth.
•Earthquakes can occur beneath the
causing giant waves called
.
Seismic Waves
•Most earthquakes occur between a depth of
and
km below the earth’s surface.
•Some occur as deep as
km below the earth’s surface.
•Where an earthquake occurs (and the rocks break and move) is called the
. The spot on the Earth’s surface directly above the focus is
called the
.
•The energy released in an earthquake moves throughout the earth as
which are like
waves.
Seismic Waves
•There are
main types of seismic waves:
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–
–
–
Seismic Waves
•Seismic waves
off of any
that they hit and tell geologists a lot about what makes up the
of the Earth.
Primary Waves
•Primary Waves (P-Waves) are the seismic waves that travel the
•P-waves can travel through
,
and
.
•P-waves have a
motion.
Secondary Waves
•Secondary Waves (s-waves)
•S-waves cause rocks to move in a
•S-waves can travel through
.
travel as fast as p-waves.
motion.
only (not liquids and gases).
Surface Waves
•Surface originate at the Earth’s surface at the
and travel the
of all the wave types.
•Surface waves cause the Earth’s surface to tumble
and
.
–Therefore, surface waves cause the most
The Seismograph
•A seismograph is a
and
to
in an earthquake.
that geologists use to measure seismic
waves.
•Using a seismograph, geologists can determine
and how
,
an earthquake was.
Seismologists
•Seismologists are geologists who study
.
•They use the
to measure the strength of an
earthquake.
•The Richter Scale goes from
to
.
–A 2.0 earthquake is
times more powerful than a 1.0 earthquake.
–A 3.0 earthquake is
times more powerful than a 1.0 earthquake.
–A 4.0 earthquake is
times more powerful than a 1.0 earthquake!
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Seismologists
•Seismologists analyze the data from
to determine the
different waves and motions.
Predicting Earthquakes
•There is
guaranteed way to predict and earthquake.
•Geologists are continuing to research signs that an earthquake is coming.
Ch. 11-2: Formation of a Volcano Key Terms
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Ch. 11-2: Why Do I Need To Know This?
•Because volcanoes are HOT!
•Because volcanoes can and do cause tens of thousands of deaths.
•Because California has many active, dormant and extinct volcanoes.
Formation of a Volcano
•Deep within the Earth, rocks melt under tremendous
and
.
•The melted rocks, called
, begins to
toward the surface of the Earth.
•As the magma rises, it stores up underground in
.
•Eventually, the magma reaches the surface of the Earth. The opening through which the magma
erupts is called a
.
•When magma reaches the surface of the Earth, it is called
.
Volcanic Eruptions
•Not all volcanic eruptions are the
.
–Some are extremely
and violent.
–Others are slow and
.
•The type of volcanic eruption that happens depends on the amount of dissolved
(
and
) and the type of magma being erupted.
3
Extrusive Igneous Rocks
•These are igneous rocks that formed at the Earth’s
•Extrusive rocks can have glassy, fine-grained or porphyritic textures.
•They may also show signs of lots of
bubbles in them.
•The most common forms of extrusive igneous rocks are
and
.
,
.
Types of Volcanoes
•There are 3 main types of volcanoes that form. They are:
–
–
–
•The type of volcano that forms depends upon the type of
being
.
that is
Cinder Cones
•Cinder cones are made up of lots of volcanic
, volcanic
and other rock debris from a small eruption.
•Cinder cones have steep sides and are only a
feet tall at most.
•Cinder cones last for about
years or so before
Shield Volcanoes
•Shield volcanoes form from
, which flows very
•Consequently, they tend to form big, broad and
volcanoes.
•The
(and almost all other volcanic islands) are examples of
.
.
volcanoes.
Composite Volcanoes
•Composite volcanoes are formed by alternating layers of
and
.
•Composite volcanoes have
slopes.
•Composite volcanoes are formed by
and/or
•Composite volcanoes are the most common form of volcano on the
Calderas
•When a volcano is done erupting, there is usually a funnel-shaped
in the ground from which the lava erupted. This is called a
.
•Often, when a volcano is
erupting, the underground
is empty and collapses. This is called a
.
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.
.
Volcanic Activity
•Volcanic eruptions are
•An
to
is one that erupts either
or periodically.
•A volcano that has been known to erupt within
not now active is called a
volcano.
•A volcano that has not been known to erupt in
considered
.
.
, but is
is
Ch. 11-3: Volcano and Earthquake Zones Key Terms
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Ch. 11-3: Why Do I Need To Know This?
•Because we live in California, one of the most geologically
states in the country.
•Because California is part of the
•To better understand
.
.
Volcano and Earthquake Zones
•Volcanoes and earthquakes tend to occur in the same parts of the world.
.
•These are:
–
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–
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