Geology
The Franklin Mountains are 23 miles (37 km) long and 3 miles (4.8 km) wide) and stretch from El Paso into New Mexico. The Franklins were formed due to crustal extension related to the Cenozoic Rio Grande rift. Although the present topography of the range and adjoining basins is controlled by extension during rifting in the last 10 million years, faults within the range also record deformation during the Laramide orogeny, between 85 and 45 million years ago.
The mountains are the southernmost tip of the Rocky Mountains in the U.S. The Precambrian rocks atop North Franklin Mountain are "the highest geological structure in the state of Texas." The highest peak is North Franklin Mountain at 7,192 feet (2,192 m). North Franklin Peak can be accessed via a trail located east of Mundy's Gap. The mountains are composed primarily of sedimentary rock with some igneous intrusions. Geologists refer to them as tilted-block fault mountains and in them can be found billion-year-old Precambrian rocks, the oldest in Texas.
Read more about this topic: Franklin Mountains State Park