- Balcones Fault
The Balcones Fault is a zone of normal faulting in
Texas (USA) that runs approximately from the southwest part of the state to the north central region alongInterstate 35 . Like most fault zones, the Balcones Fault zone is made up of many small, mostly unnamed faults. One of the more well-known faults within the zone is theMount Bonnell Fault, which runs through central and west Austin.The location of the fault zone may be related to the
Ouachita Mountains , formed 300 million years ago during a continental collision. Although long-since eroded away in Texas, the roots of these ancient mountains still exist, buried beneath thousands of feet ofsediment . These buriedOuachita Mountains may still be an area of weakness that becomes a preferred site for faulting when stress exists in the Earth's crust. The Balcones Fault zone was most recently active about 15 million years ago during theMiocene epoch. This activity was related tosubsidence of theTexas Coastal Plain , most likely from the large amount of sediment deposited on it by Texas rivers. The Balcones Fault zone is not active today, and is in one of the [http://earthquake.usgs.gov/hazmaps/products_data/2002/2002April03/US/USpga500v4.giflowest risk zones] forearthquake s in the United States.The surface expression of the fault is the Balcones
Escarpment , which forms the eastern boundary of theTexas Hill Country and the western boundary of the Texas Coastal Plain and consists of cliffs and cliff-like structures.Many cities are located along this fault zone, and that is not a coincidence. Frequently, springs such as
San Pedro Springs , Comal Springs,San Marcos Springs ,Barton Springs andSalado Springs are found in the fault zone and provide a source of fresh water and an obvious place for human settlement.External links
* [http://www.lib.utexas.edu/geo/balcones_escarpment/contents.html The Balcones Escarpment :Geology, Hydrology, Ecology and Social Development in Central Texas]
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