Balcones Fault

[4] 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 worn away in Texas, the roots of these ancient mountains still exist, buried beneath thousands of feet of sediment.

These buried Ouachita Mountains[5] 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.

The Balcones Fault Zone[8] is a demarcation line for certain ecological systems and for species distributions, e.g., the California fan palm (Washingtonia filifera) is the only species of palm tree native to the continental United States west of the Balcones Fault.

Escarpment formed by the Balcones Fault at Mount Bonnell
Balcones Fault Trend and affected counties
Geologic map of the Balcones, and the Mexia-Talco-Luling Fault Trends, where black lines are faults, the blue shaded area is the Claiborne Group, yellow is the Jackson Group, and tan is the Wilcox Group