It’s your fault!

Folding and faulting of rocks

The stresses of crustal rock

As you learned last section, stress causes strain in crustal rock in three ways.Rocks respond to this stress similar to the way a spring responds – it deforms, then restores itself if the force is removed.If enough stress is applied, the rock may change form completely (by folding) or by breaking (faulting).

What happens when rocks fold?

No, it doesn’t mean they throw their hand away.

It DOES mean they change shape without breaking!

Three types of folds are produced on rocks in this way.

This is an anticline – notice the man standing next to the formation for scale.

Anticlines and SynclinesMuch like the folding of a tablecloth, rocks generally form this way as a result of compression.Most anticlines and synclines are found together.Look for examples of this next time you are on a highway carved out of a rocky area.Death valley is an example of a

large-scale syncline.

MonoclinesWhen the mantle pushes up on crustal rock, or due to isostatic adjustments, monoclines are formed.

You can also see examples of horizontal layers changing elevation throughout the country.

Faulting

Generally stress continues to be applied to areas where you see folding formations.

Eventually because of this stress, the rock will fault.

Faulting is a break in rock, and can happen in numerous combinations of the following methods.

The various types of faults.

Fault notes

While most large-scale earthquake causing faults are plate boundaries, rocks fault in mountains frequently, and less frequently in flatter areas.

The way to tell the difference between normal and reverse/thrust faults is one part of the rock is being pushed over the other in a reverse/thrust fault.

Strike-slip faults are commonly found at transform plate boundaries, like the San Andreas fault.