City of Rocks State Park
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Cooke blazed a trail south of the park to link newly acquired New Mexico and Arizona with the eastern United States. The mountain range southeast of City of Rocks is named Cooke’s Range after Captain Cooke. The prominant peak in the southern part of the range is Cooke’s Peak.
The Butterfield Overland Mail Route began in 1858 and passed south of the park. It ceased to operate in 1861 because of the Civil War.
Fort Cummings was established in 1863 at Cooke’s Spring near the park to protect travelers from Apache Indians. The fort was abandoned in 1886 when danger from the Indians ended.
The railroad reached Deming in 1881 bypassing City of Rocks, although settlers coming into the area camped and picnicked at the site for decades, just as people do today.
Faywood Hot Springs lies south of City of Rocks State Park, but unlike City of Rocks, it is private property. The Mimbres Indians also left their pottery and other artifacts at this site. In the 1850’s, the springs were known as Ojo Toro, or Bull Spring, because wild bulls would graze at this site. Stagecoach lines stopped at the springs during the mid- to- late 1800’s. In 1862, Colonel Richard Hudson settled in the area and built a resort at the springs known as Hudson Hot Springs Sanitarium Company. The resort became one of the famous spas in the west. The water was even bottled and shipped out of the state. The hotel burned down in 1891. New owners, J. C. Fay and William Lockwood, rebuilt the complex and renamed it Faywood after both men. The new hotel could accomodate 100 guests. Visitors traveling on the Atchison, Topeka, and Santa Fe Railroad could disembark at what was then the Faywood Station.
The rocks forming the City of Rocks, the Kneeling Nun Tuff, were produced by a very large volcanic eruption that occurred 34.9 million years ago. The Kneeling Nun Tuff was formed by a violent eruption of volcanic pumice, ash, and hot gas in an eruption 1000 times greater than the May 18, 1980 eruption of Mount St. Helens. The entire eruption of the Kneeling Nun Tuff would have taken from months to years. The history and style of eruption can be determined by studying the rock seen at City of Rocks, and elsewhere.
The initial stages of the Kneeling Nun eruption are likely to have produced large volumes of pumice that rained out of the sky, blanketing the surrounding countryside. This stage is referred to as the plinian eruptive phase. The magma that produced the eruption was probably located between 6 and 15 kilometers below the earth’s surface. A pipe, or conduit, formed between the magma chamber and the earth’s surface, allowing the magma to escape through a volcanic vent.
The main phase of the Kneeling Nun eruption was the most violent. During this time, close to 1000 cubic kilometers of volcanic pumice, ash, and gas were erupted through the volcanic vent that had been formed by the earlier plinian eruption. The vent would widen during the main eruptive phase, allowing large amounts of volcanic material to erupt very quickly. This material would move as a large, hot, turbulent cloud, traveling as far as 200 kilometers from the vent, and depositing volcanic material in it’s path. This phase is called ignimbrite eruption.
The layer of volcanic material produced by the ignimbrite eruption was still very hot at the time it was deposited. Because of this heat, the volcanic fragments in the layer of volcanic material compacted, or welded, to form the dense rock that you see at City of Rocks today. The rock layer is thickest near the vent, and becomes progressively thinner with distance from the vent area. City of Rocks is around 30 kilometers from the vent of the Kneeling Nun Tuff, residual heat from the magma chamber could have produced thermal areas and hot springs, such as are observed today at Yellowstone National Park, and in the Jemez Mountains in New Mexico.
The formation of the columnar landforms that we see at City of Rocks today would have begun shortly after the main eruption of the Kneeling Nun Tuff. The timing of the formation of the pinnacles is not known, but is likely to have taken many millions of years. Erosion and modification of the pinnacles continues today by a combination of freeze- thaw action, wind and effects of vegetation.
During cooling of the Kneeling Nun Tuff, cooling cracks, or joints, would have formed. These joints form perpendicular to the cooling surfaces, so are oriented perpendicular to the ground surface.
Through time, the cooling joints and other cracks are widened by a number of erosional processes. Freeze- thaw action and wind are two major factors, and vegetation growing into cracks, and acid produced by vegetation may be important as well. As material in the cracks becomes loosened by freeze- thaw and vegetation, finersized material is stripped away by the wind, causing the cracks to become enlarged.
The length of time required to form the current City of Rocks is not well known. However the multiple flares observed in the pillars suggests that several major periods of weathering have occurred and that the pillars may have formed in a series of episodes, rather than by a slow, continous process.
Continued erosion and modification of the pillar shape continues today and, in several million years, the City of Rocks may be eroded to a flat plane, while other “City of Rocks” may have been formed in other similar volcanic deposits in the area.
To the north- northeast, the prominant peak is Mimbres Peak on Whitehorse Mountain, composed entirely of volcanic rocks. Possibly visible on the distant skyline beyond is the crest of the Black Range, one of the major mountain ranges in New Mexico.
Nearby, to the northeast, is Table Mountain with an upper and lower cliff of welded rhyolite tuff and slopes of softer bedded rhyolite tuffs, all part of the Sugarlump Formation. To the east is Round Mountain, composed of andesite and latite flows, breccias, and tuffs.
Cooke’s Peak, a prominent landmark, pierces the skyline to the east- southeast. The peak is a massive body of granodiorite, an intrusive igneous rock similar in appearance to granite. The granodiorite was injected as a hot, molten mass into a thick sequence of sedimentary rocks consisting of limestone, sandstone, and shale. Some of these sediments, particularly the limestones, contain a fossil record of former seas that covered this region nearly 500 million years ago!
Just to the right of Cooke’s Peak, and only a little more than 4 miles away, is the intrusive rhyolite dome of Taylor Mountain at the western foot of which lies the channel of the Mimbres River.
On the horizon to the southeast are the jagged peaks of the Florida Mountains, jutting abruptly upward from the flat surface of the Deming Plain.
Nearer, to the south- southeast, is the basaltcapped volcanic peak of Black Mountain, beyond and to the right of which is Red Mountain. Volcanic peaks cluster about Grandmother Mountain to the south- southwest and farther to the southwest where the highest is Soldier’s Farewell Hill. Nearly due west on the horizon is the broad crest of the Big Burro Mountains.
The pale- colored band of mill tailings from the Hurley mill of Kennecott Copper Corporation is to the west- northwest. In the middle distance to the northwest are the volcanic Cobre Mountains, which overlook the Chino mine on the north side. Beyond, on the distant skyline, is the Pinos Altos Range, also composed of volcanic rocks.