The mountains are unusual, and perhaps unique in New Mexico, for the relatively complete geologic history revealed by their rocks.

The types, sizes, and profiles of the Caballo watersheds vary significantly according to the part of the range that they drain.

No perennial streams flow through the mountains, although the course of the Rio Grande is close to the north, west, and south margins of the range.

Water falling on the precipitous west face of the range drains directly into the Rio Grande by means of numerous first order canyons with high gradients.

This allows not only the identification of the older and younger formations, but conclusions about unusual local conditions, such as folding, a fault displacement, or an unconformity.

Absolute dating measures the presence and ratios of chemicals within the rocks to determine the number of years since they were deposited.

By studying plant and animal fossils that may exist in the formation, it may be possible to determine not only its relative age, but the climate at the time of deposition.

The Caballo Mountains are essentially unique in New Mexico because their section of exposed rocks begins in Precambrian time, and runs through every geological period of the Phanerozoic eon with the exceptions of the Triassic and Jurassic.

Throughout the early and middle Paleozoic southern New Mexico alternated between being flooded by shallow tropical seas, and being exposed to erosion.

In the Caballo Mountains, this can be seen in the Palm Park Formation, a thick layer of andesitic or tuffaceous mudstones, sandstones, and breccia.

In the southern part of the Caballo Mountains, there are remnants of a region wide sheet of flood basalts and andesite, which was laid during the Oligocene.

On the west side of the range along the Rio Grande, the alluvial fill consists of unconsolidated fluvial deposits of boulders, cobble, and gravel.

[2] It is the product of extensional tectonic (or divergent) forces that formed a series of basins between the Colorado Plateau and the North American craton[3] Thin continental crust, normal fault block topography, high regional elevation, and volcanism is found over the course of the rift.

Activity in the vicinity of the Caballos during the first stage included explosive rhyolitic eruptions from cauldrons located to the northwest, west, and southeast.

Approximately 9.6 Ma, the eruption of basalts near Fort Selden signaled the renewal of crustal extension and volcanism in the southern part of the rift.

Production has been concentrated in three areas: It has been estimated that the total value of copper, silver, gold, and lead produced from the Caballos before 1952 did not exceed $200,000.

With the exception of the intermittent streams in the northern part of the range, and the area in close proximity to the Rio Grande, there is very little permanent water.

Common birds of prey include golden eagles (Aquila chrysaetos), Swainson's hawk (Buteo swainsoni), Northern harrier (Circus cyaneus), and burrowing owl (Athene cunicularia).