Pamela J. W. Gore
Georgia Perimeter College

A fault is a crack in the Earth's crust along which movement has occurred.

Animation by Charlie Watson, Seismo-Watch

Types of faults:

  1. Dip-slip faults
    Movement along dip-slip faults is vertical; one side moves up and the other side moves down.

    1. Normal fault
    2. Reverse fault
      1. Thrust fault - a low angle reverse fault

    Normal Faults
    Cambrian Kinsers Formation
    Thomasville Quarry, Pennsylvania

    Horst and graben terrane, seen in the Basin and Range Province of the western U. S., is dominated by normal faults. Compare with photo above.

    Thrust fault,
    Pennsylvanian Crab Orchard Mountain Group,
    near Ozone, Tennessee, Route 40/75 eastbound.

  2. Strike-slip faults
    Movement along strike-slip faults is horizontal.

    1. Left-lateral strike-slip fault
    2. Right-lateral strike-slip fault

    How do you tell which is which?
    Look across the fault to the other side.
    Did it move to the LEFT or to the RIGHT?

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Horst and graben diagram used with permission of Bruce E. Herbert, Texas A & M University, Big Bend Virtual Field Trip

This page created by Pamela J. W. Gore
Georgia Perimeter College, Clarkston, GA

Page created March 31, 1996
Modified May 6, 1997
Modified December 16, 1998
Last modified July 17, 1999
Links updated August 15, 2009