Chapter 11, Section 1 Forces Inside the Earth

Elastic Deformation

• The ability of an object to bend and stretch without breaking.

Elastic Limit

• The point at which an object that has elasticity breaks.

Rocks and Elasticity

• Rocks will bend and stretch in response to forces within the Earth until they reach an elastic limit, at which time they break.

Review of Forces• Compression– Pushes/squeezes rocks together

• Tension– Pulls rocks apart

• Shearing– Slides rocks past each other

Faults

• Occur when rocks reach an elastic limit and break.

• Rocks on either side of the break move.

Anatomy of a Fault

• Fault Plane– Surface of the

fault.

• Hanging Wall– Rocks above

the fault plane.

• Foot Wall– Rocks below

the fault plane.

Faults

• 3 types:– Normal faults– Reverse faults– Strike-slip faults

Faults• Normal Fault– Rocks in the hanging wall move down relative

to the rocks in the footwall.– Caused by tension

Faults• Reverse Fault– Rocks in the hanging wall move up relative

to the rocks in the footwall.– Caused by compression.– Thrust fault

• Special type of reverse fault where the rocks in the hanging wall are pushed up and over the rocks in the foot wall at a very low angle.

• Common in steep mountains.

Faults• Strike-slip faults– Rocks on either side of the fault plane

are moving past each other with little up or down motion.