I took this photograph yesterday from the Davis Mountains Scenic Loop about 4 miles from the 166/17 junction just south of Fort Davis.
The Haystacks on the left horizon are twin trachyte intrusions (6,895 and 6,670 feet). Their age is unknown; a nearby intrusion was dated at 34.6 Ma, about 700,000 years after the main phase of volcanic activity in the Davis Mountains ended. The peaks are called Twin Mountains on U.S. Geological Survey topographic maps.
On the right horizon, the Puertacitas Mountains are an eroded series of basalts and tuffs, 1,250-feet thick, that erupted from nearby vents in one of the later volcanic episodes. One vent has been identified between the Puertacitas Mountains and the Haystacks.
The Mano Prieto Mountains are in mid-photograph, a series of small hills composed of Sleeping Lion and Barrel Springs volcanic strata about 35 million years old.
Younger basalt lava outcrops can be seen on the far left of the photograph.
