Download Whose fault is it? Name: Block: Background: The crust can move

Whose fault is it?
Name:
Block:
Background:
The crust can move vertically as well as laterally. One cause of vertical motions is
isostasy. The lithosphere was a certain weight that is being pulled by gravity. The
buoyant asthenosphere tries to push upon a plate. If a mountain erodes and the weight
lessens on the asthenosphere the area can sometimes move upwards under the buoyant
force of the asthenosphere in a process called uplift. If an area is weighted the rock can
deform downwards into the asthenosphere. Motions can also be the result of stress. As
the lithosphere moves it exerts forces on the rock called stress. Stress that squeezes a
rock body is called compression which often occurs in places near convergent
boundaries. Stress that pulls and lengthens a rock body is called tension and occur along
faults near divergent boundaries. Shearing is a stress applied laterally in opposite
directions that is common along faults near transform boundaries. As stress and strain
builds in the rock it can break and move, creating a fault. The area along which rock
moves is called the fault plane. Rock above the fault plane is called the hanging wall
and the rock below the fault plane is called the footwall. To find the hanging wall, locate
a spot along your fault where you have rock on either side; the rock overlying your spot
is the hanging wall. The rock underneath the fault line is the foot wall.
footwall Hanging
wall
Hanging
footwall
wall
Types of faults:
Normal fault: when the footwall moves up relative to the hanging wall. This is typical
with tension
Reverse fault: when the footwall moves down relative to the hanging wall, typical of
compression
Thrust fault: a special type of reverse fault when the fault is at a low angle.
Strike slip fault: these have lateral but not vertical motions found near transform
boundaries. They are classfied as right lateral if when standing on the fault the motion
appears to go to the right and left lateral if when standing on the fault fit appears to go
left.
Directions:
On each diagram
1) label the hanging wall and footwall (this might not be possible for top view
diagrams)
2) draw arrows indocating the direction each block moved 3) indicate the type of
fault
3) indicate the type of stress
4) indicate the type of plate boundary it would likely be near.
Each diagram is a side view unless indicated
a
Top view