Download Types of Faults

Types of Faults
Rocks Move Along Faults
• Fault:
– Fracture, or break, in Earth’s lithosphere, where
blocks of rock move past each other
• At some parts of a fault, the rock slides slowly
or constantly. At others it sticks or locks
together.
– Rock bends as stress is put on it (the force exerted
when an object presses on, pulls on, or pushes
against another object.)
Earthquake
• Earthquake
– shaking of the ground caused by the sudden
movement of large blocks of rock along a fault
– can occur when there is a sudden release of stress
in the lithosphere.
• Release of stress occurs when the rocks break free from
being stuck
• Strength of an earthquake depends on
– The amount of stress built up
– The distance the rocks move along the fault
The rocks that move
• Most faults are along tectonic plate boundaries
– Most earthquakes occur here
• The rocks that move during an earthquake are
smaller than tectonic plates
• A small percentage of earthquakes occur along faults
within plates
– Stress along a plate boundary can cause the rocks to break
and move along weak areas in the middle of the plate.
Types of faults
• Faults are classified base on how they move
– How they move is determined by the kind of
stress that they are under.
• More than one type of fault may be present
along the same boundary.
Normal Fault
• The block of rock above the
fault plane slides down
relative to the other block
• Occurs when stress pulls the
rocks apart
• Earthquakes are common
near boundaries where
tectonic plates are moving
apart
– The Great Rift Valley of Africa.
Reverse Fault
• The block of rock above
the fault plane moves
up relative to the other
block
• Occurs when stress
presses rocks together
• Occurs near collisionzone boundaries
between plates
Strike Slip Faults
• Blocks of rock move
sideways on either side
of the fault plane.
• Occurs when stress
pushed rocks
horizontally
• Happens when plates
scrape past each other