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Transcript
Earthquakes
Warm-Up
1. How does the process of subduction
recycle rock?
2. How can magma rise up on the ocean
floor?
3. What happens to rock to form folded
mountain ranges?
4. Explain how Earthquakes occur.
5. How can new ocean floor be created?
6. How do mountain ranges form?
7. Why is density important at subduction
zones?
An Earthquake is…
• The movement of
Earth's plates produces
strong forces that
squeeze or pull the rock
in the crust. We feel
this as shaking and
trembling.
• Stress is a force that
acts on rock to change
its volume or shape
• Deformation is the
disruption of the
original form of rocks
3 Types of Stress
There are three
different types of
stress that occur on
the crust, shearing,
tension, and
compression
These forces cause
some rocks to become
fragile and they snap
Some other rocks
tend to bend slowly
like road tar softened
by the suns heat
Faults
A fault is a break in the
crust where slabs of
crust slip past each
other. The rocks on both
sides of a fault can move
up or down or sideways
When enough stress
builds on a rock, the
rock shatters, creating
faults
Faults usually occur along
plate boundaries, where
the forces of plate
motion compress, pull, or
shear the crust too much
so the crust smashes
Strike-Slip Faults
Shearing creates a
Strike-Slip Fault
In this fault, rocks
on both sides of the
fault slide past each
other with a little up
and down motion
When a strike-slip
fault forms the
boundary between
two plates, it
becomes a transform
boundary
Normal Faults
Tension forces in Earth's
crust causes Normal faults
Normal faults are at an angle,
so one piece of rock is above
the fault, while the other is
below the fault
The above rock is called the
hanging wall, and the one below
is called the footwall
When movement affects along
a normal fault, the hanging wall
slips downward
Normal faults occur along the
Rio Grande rift valley in New
Mexico, where two pieces of
Earth's crust are diverging
Reverse Faults
Compression forces
produce Reverse fault
This fault has the same
setup as a normal fault,
but reversed, which
explains it’s name
Just like the normal fault,
one side of the reverse
fault is at an angle of the
other
This fault produced part
of the Appalachian
Mountains in the eastern
United States
How Do Mountains Form?
The forces of plate
movement can build up
Earth's surface, so over
millions of years,
movement of faults can
change a perfectly flat
plain into a gigantic
mountain range
Sometimes, a normal
fault uplifts a block of
rock, so a fault-block
mountain forms
When a piece of rock
between two normal
faults slips down, a
valley is created
Anticlines and Synclines
Geologists use the
terms syncline and
anticline to describe
downward and upward
folds in rock
An anticline is a fold in a
rock that arcs upward
A syncline is a fold in a
rock that arcs
downward
These folds in rocks are
found on many parts of
the earths surface
where compression
forces have folded the
crust
Seismic Waves
Seismic Waves:
vibrations that travel
through Earth carrying
the energy released
during an earthquake
an earthquake produces
vibrations called waves
that carry energy while
they travel out through
solid material
During an earthquake,
seismic waves go out in
all directions to the
focus
They ripple like when
you through a stone into
a lake or pond
Seismic Waves Ctd.
There are three
different types of
seismic waves:
Primary waves,
Secondary waves,
and surface waves
The Richter Scale
-The amount of damage created by an
earthquake depends on several factors.
-Measures an earthquake’s strength
Magnitude
-Number that represents the measurement
of an earthquake on the Ricter Schale