Notes on Basic Geology
Notes created & information organization based on the book:
The Dynamic Earth - an introduction to physical geology"
Brian Skinner & Stephen C. Porter   (further book information here)
also look at for additional resource information
Deformation - Page 5

Normal Faults - special cases

A horst and a graben are special types of normal faults, they both require two parallel faults to form.

The graben is defined by a large sinking block between two footwalls. Each side of the graben is a hanging wall. Such structures can form valleys or river basins.

A horst is formed when a central block rises up relative to two other blocks.

The horst has a footwall on each side and rises up relative to the two hanging wall units on each side.

Idaho, King Hill area
(false color)
Reverse Faults - special case

A thrust fault is a low angle fault often associated with mountain ranges. The hanging wall often shows a very high rise relative to the foot wall as much as several km.

It brings much older strata to a position above the younger strata. Over time the raised hanging wall is often eroded back away from the fault and forms a mountain environment.

Limestone thrust faulted
over shale, Presidio Co., Texas
(false color)
Strike Slip Faults -
The best known strike slip fault in the world is the San Andreas fault. It runs from south of the Gulf of Mexico and extends through part of California and runs all the way to Alaska.
USGS:Source 3 photos of San Andreas fault (California) (fault line shown with yellow line)
Bending Deformations

There are three "typed" bending deformations:

1.) Monocline: one sided displacement (smooth)
2.) Anticline: center rises displacement
3.) Syncline: center falls displacement

USGS:Source ----- (Colorado monocline) ---------- (Utah syncline)--------------- (Montana anticline)