Balcones, and the Mexia-Talco-Luling Fault Trends

The Balcones Fault or Balcones Fault Zone is an area of largely normal faulting Edwards Aquifer in the

U.S. state In the United States, a state is a constituent political entity, of which there are 50. Bound together in a political union, each state holds governmental jurisdiction over a separate and defined geographic territory where it shares its sove ...

Texas Texas (, ; Spanish: ''Texas'', ''Tejas'') is a state in the South Central region of the United States. At 268,596 square miles (695,662 km2), and with more than 29.1 million residents in 2020, it is the second-largest U.S. state by ...

that runs roughly from the southwest part of the state near Del Rio to the north-central region near

Dallas Dallas () is the List of municipalities in Texas, third largest city in Texas and the largest city in the Dallas–Fort Worth metroplex, the List of metropolitan statistical areas, fourth-largest metropolitan area in the United States at 7.5 ...

along

Interstate 35 Interstate 35 (I-35) is a major Interstate Highway in the central United States. As with most primary Interstates that end in a five, it is a major cross-country, north–south route. It stretches from Laredo, Texas, near the Mexican border ...

. The Balcones Fault zone is made up of many smaller features, including

normal fault In geology, a fault is a planar fracture or discontinuity in a volume of rock across which there has been significant displacement as a result of rock-mass movements. Large faults within Earth's crust result from the action of plate tecton ...

s, grabens, and horsts. One of the obvious features is the

Mount Bonnell Mount Bonnell , also known as Covert Park, is a prominent point alongside the Lake Austin portion of the Colorado River (Texas), Colorado River in Austin, Texas. It has been a popular tourist destination since the 1850s. The mount provides a vista ...

Fault. The location of the fault zone may be related to the

Ouachita Mountains The Ouachita Mountains (), simply referred to as the Ouachitas, are a mountain range in western Arkansas and southeastern Oklahoma. They are formed by a thick succession of highly deformed Paleozoic strata constituting the Ouachita Fold and Thru ...

, formed 300 million years ago during a continental collision. Although long since worn away in Texas, the roots of these ancient mountains still exist, buried beneath thousands of feet of

sediment Sediment is a naturally occurring material that is broken down by processes of weathering and erosion, and is subsequently transported by the action of wind, water, or ice or by the force of gravity acting on the particles. For example, sa ...

. These buried Ouachita Mountains J.S. Aber 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 has remained inactive for nearly 15 million years, with the last activity being during the Neogene period. This activity was related to subsidence of the

Texas Coastal Plain The Texas Coastal Bend, or just the Coastal Bend, is a geographical region in the US state of Texas. The name refers to the area being a curve along the Texas Gulf Coast of the Gulf of Mexico. The largest city of the Coastal Bend is Corpus Christ ...

, most likely from the large amount of sediment deposited on it by Texas rivers. The Balcones Fault is in one of the lowest-risk zones for

earthquake An earthquake (also known as a quake, tremor or temblor) is the shaking of the surface of the Earth resulting from a sudden release of energy in the Earth's lithosphere that creates seismic waves. Earthquakes can range in intensity, fr ...

s in the United States. The surface expression of the fault is the Balcones Escarpment, Texas State Historical Association which forms the eastern boundary of the Texas Hill Country and the western boundary of the Texas Coastal Plain, and consists of cliffs and cliff-like structures. Subterranean features such as Wonder Cave and numerous other smaller caves are found along the fault zone. Many cities are located along this fault zone. Springs such as

San Pedro Springs San Pedro Springs is the name of a cluster of springs in Bexar County, Texas, U.S.A. These springs provide water for San Pedro Creek, which flows into the San Antonio River. The San Antonio Springs also feed into the San Antonio River. Natural ...

, Comal Springs,

San Marcos Springs San Marcos Springs is the second largest natural cluster of springs in Texas. The springs are located in the city of San Marcos, Texas, about 30 miles (48 km) southwest of Austin and 46 miles (74 km) northeast of San Antonio. Althoug ...

, Barton Springs, and

Salado Springs Salado Springs is the name of five groups of springs at the town of Salado in Bell County, Texas, in the United States. The springs are located 48 miles (77 km) north of Austin or 135 miles (217 km) south of Dallas. The springs, wh ...

are found in the fault zone and provide a source of fresh water and a place for human settlement. The Balcones Fault Zone UT Austin is a demarcation line for certain ecological systems and species distributions, e.g., the California fan palm (''

Washingtonia filifera ''Washingtonia filifera'', the desert fan palm, California fan palm, or California palm,Flora of North America Association. ''Flora of North America: North of Mexico Volume 22: Magnoliophyta: Alismatidae, Arecidae, Commelinidae (in Part), and Zi ...

'') is the only species of

palm tree The Arecaceae is a family of perennial flowering plants in the monocot order Arecales. Their growth form can be climbers, shrubs, tree-like and stemless plants, all commonly known as palms. Those having a tree-like form are called palm ...

native to the continental United States west of the Balcones Fault.

References

External links

The Balcones Escarpment :Geology, Hydrology, Ecology and Social Development in Central Texas
{{Texas Escarpments of the United States Geology of Texas Landforms of Texas Seismic faults of the United States

See also

References

External links