Earth’s Crust in
Motion
Chapter 5.1
What is an
earthquake?
What causes
earthquakes?
• Earthquake: The shaking and
trembling that comes from the
movement of rock beneath Earth’s
surface.
• When the tectonic plates of
Earth’s lithosphere move they
cause stress on the crust.
What is
stress?
• Stress: A force that acts on rock
to change its shape or volume.
Stress adds energy to the rock.
How does it
Create
earthquakes?
• Stress builds up until there is
enough energy to overcome the
friction, and the land shifts.
• The more energy built up, the
bigger the quake.
• What is
Friction
• Friction is the force that opposes the
motion of one surface as it moves
across another surface. Friction
exists because surfaces are not
perfectly smooth.
• Rocks move along a fault depending
on how much friction there is
between opposite sides of the fault.
• How_Does_Plate_Movement_Gener
ate_Earthquakes
• Three Types of Stress
Are there
• Shearing , Tension and
Compression
different types
of stress?
What are
they?
• Shearing
Pushes a mass of rock in two
opposite directions. Rock
breaks, slips apart or changes
its shape.
• Tension
Pulls on the crust, stretching rock so
that it becomes thinner in the
middle. It occurs where two plates
are moving apart.
• Stress video
Compression
• Squeezes rock until it breaks. One
plate pushing on another compresses
rock like a trash compactor.
• What are
faults?
Where do
they occur?
• Faults
• Fault: A break in Earth’s crust where
slabs of crust slip past each other.
Faults occur when enough stress
builds up in rock to make it break.
• Describe and • Three Types of Faults
draw the
• 1) Strike Slip Faults
three types
• Found at transform boundaries
of Faults.
• The rocks on either side of the fault
slip past each other sideways with
little up or down motion
• Ex: San Andreas Fault.
strike slip video
strike-slip fault animation
• What is the
•
difference
•
between a
•
hanging wall
and a
footwall?
• normal fault
animation
Normal Faults
Found at divergent boundaries.
Tension forces in Earth’s crust
cause normal faults. The fault is at
an angle, so one block of rock lies
above the fault while the other block
lies below the fault. There is up and
down motion.
•
•
Hanging Wall lies above
Footwall  lies below
Normal Fault Animation
•
•
•
Reverse Faults.
Found at convergent boundaries
The same structure as a normal
fault, but the blocks move in the
opposite direction. The rock
forming the hanging rock slides UP
& OVER the foot wall.
reverse fault animation
Fault animation
more
animation
More Animation
Type of
Stress
Type of
Plate
Boundary
Type of
Fault