City of Rocks State Park

Faywood, New Mexico – January 8, 2023

One day – I think it was a Tuesday but I could definitely be wrong – about 35 million years ago, a volcano began erupting in what is now southwestern New Mexico.

Somewhat later, on January 8, 2023, Nancy, Gunther and I visited City of Rocks State Park, located about 20 miles south of the caldera that produced the eruptions. The pumice and other rocks produced by the volcano’s eruptions 35 million years ago form the main feature of the state park, which also has a number of interconnected hiking trails, developed campsites, a botanic garden, and even an astronomical observatory.

We’d planned to visit he park, which is located halfway between Deming and Silver City, New Mexico, just a few miles east of U.S. Route 180, several times in 2021 and 2022 when we were camping in Deming and Silver City. However, the 35 mile-per-hour winds each of those days convinced us to find something else to do. The morning of January 8 was bright and calm, and we made the short trip to the state park. We’re all glad that we did.

You’ll find plenty of prickly pear cactus at City of Rocks State Park in New Mexico, along with a wide variety of other plants. In the background, a vehicle provides a sense of scale for the namesake rocks near the park’s visitor center.

The park, at an elevation of just over 5,200 feet, gets its name from several tall outcroppings of rock that have eroded over the past 35 million years into pinnacles and other formations, separated by lanes that resemble city streets between tall buildings.

Here we see an amateur geologist, with her professional dog, on one of the park’s trails. They appear to be in disagreement about which direction to proceed. The park has about five miles of trails, some of which wind directly through the rock formations. Many of the pinnacles are 40 feet tall.

Paths between the rocks can get pretty tight. During the main phase of the volcano’s eruption, more than 240 cubic miles – about twice the volume of Lake Erie – of pumice and ash were ejected. This eruption also resulted in the “Kneeling Nun” formation east of present-day Silver City, 20 miles to the north. The pointed mountain seen between the two rocks is Cookes Peak (elev. 8,408 feet), a significant landmark in southwestern New Mexico. The mountain is directly north of the city of Deming.

The volcanic eruption that formed the formations of City of Rocks likely lasted several years and was about a thousand times larger than the Mt. St. Helens event in Washington on May 18, 1980. The eruption blanketed this area in a deep layer of hot ash and pumice. As those volcanic materials cooled into a rock called tuff, it shrank somewhat and vertical cracks in the stone were created.

They still haven’t agreed on a direction in which to hike. The park has a huge variety of succulents, like the soaptree yucca at the left of the trail, as well as many grasses common to the southwestern United States.

Over the last several tens of millions of years, the erosive forces of nature – water, wind, and organic growth – broadened the small fissures between the rocks into larger and larger crevices until the natural pathways seen today were created.

Now they’re both headed the same direction. The amateur geologist is standing in a crevice that is a conduit for water flowing through the rock formation. It’s that water, which carries abrasives like sand, that helped carve the rocks into the shapes we see today. Other contributors to the erosion include wind, which can also carry sand, as well as plant (and non-plant) life and the cycle of freezing and thawing water.

Many different groups of native Americans have lived in, or at least passed through, the area now known as City of Rocks. About 12,000 years ago, the last of the Ice Age glaciers were retreating and large mammals like mammoths and mastodons roamed this region. It’s likely that Paleoindians, like Clovis or Folsom peoples, hunted the large animals. Between 8,000 and 1,000 years ago, small bands of the Desert Archaic culture lived in the area and, toward then end of that era, began to build pit houses. Finally, the Mimbres culture occupied the area between the years 200 and 1150 AD. In addition to hunting animals and gathering food from plants, the Mimbres cultivated crops like beans, squash, and maize. They also built one-story above-ground dwellings.

Do you like lichen as much as I’m likin’ this lichen? There are about 20,000 known species of lichen in the world, and at least four of them can be seen in this photograph. Lichen, which is plant-like but not an actual plant, contributes slowly but significantly to the erosion of rocks by chemically degrading the stones’ minerals. The scientists estimate that between 6-8 percent of the earth’s land surface is covered by lichen. Actual plants, like succulents, grasses and shrubs, also contribute to erosion by their seeds finding purchase in small crevices in the rock and then, as the plants mature, the growing roots of the organism can cause further fracturing of the minerals.

Getting up-close and personal with the rocks allows one to see some pretty fascinating natural patterns caused by erosion. I sure hope that whoever dropped those keys comes back by to pick them up! (Just kidding – they’re mine. Still need to go back and pick them up.)

Because the park is 25 miles from the nearest city of any size, it’s a popular site for stargazing at night. This structure is an astronomical observatory located near the main campground in the park. The roof slides back onto the supports in the back to reveal the telescope. It was not in operation during our visit (as you can see, it was daylight), but the park does host regular star parties during which the observatory is open and other amateur astronomers bring their own telescopes to share views of the night skies.

This magnificent succulent specimen, about 20 yards off the trail, is desert spoon (Dasylirion wheeleri). I didn’t want to get off the trail to take a closer picture, so this will have to do. The fronds of desert spoon were used by native Americans to weave baskets and mats, and its inner core can be fermented into an alcoholic drink, similar to tequila, called sotol. It is found in southern New Mexico and Arizona, as well as parts of Texas and Mexico. The plants themselves grow to about 5 feet tall, but the flowering spike can soar 16 feet into the air.

Here’s another interesting succulent found along the trail. This long-spined, purplish prickly pear is called long-spined purplish prickly pear (really) (Opuntia macrocentra). It, too, is found in Arizona, New Mexico and Texas, along with Mexico. Like other prickly pears, the fruit of this cactus is edible and is enjoyed by animals and humans alike.

But it wasn’t simply succulents we saw – we also spied several species of sparrows! Here’s a chipping sparrow (Spizella passerina) perched in some mesquite. We’ve enjoyed seeing plenty of these pretty little birds in southern New Mexico this winter.

While most of the pictures in this posting were taken with the camera on my phone, I used my digital camera to take this photo of Cookes Peak. The tall spindly shrub in the lower left corner is ocotillo (Fouquieria splendens), which can grow to more than 30 feet in height. It is native to the Chihuahuan and Sonoran deserts in the United States and Mexico. Native Americans used different parts of the plant to address a variety of ailments, and ocotillo can also be planted to serve as a natural fence.

A short spur off the main trail took us to the top of a 300-foot hill that provided a tremendous 360-degree view of the area. In this photo, the rock formations of City of Rocks are in the midground (the white streaks above the center of the photograph are campers’ recreational vehicles parked amongst the rocks, and the light brown building to the left of the RVs is the park’s visitor center). The tallest mountains on the left horizon are the Cobre Mountains, 16 miles away, and the Pinos Altos range, 30 miles in the distance, is just to the right of the Cobre Mountains.

This eye-catching grass is cane bluestem (Bothriochloa barbinodis), a valuable forage for ranchers but one of the first grasses to disappear if a pasture is overgrazed. The seed heads catch the sun in such a way as to look absolutely illuminated from within.

When we walk by a creosote bush (lower left), I like to rub my fingers on the leaves – they smell just like the air outside after a rainstorm. Along with seemingly every other plant, Native Americans found many medicinal uses for creosote. In the background is Table Mountain, the tallest point in City of Rocks State Park. The distinct layers of rock seen on the mountain’s slopes are due to different volcanic ashflows more than 30 million years ago..

If you plan to visit City of Rocks State Park, you’ll want to do make plans to do so soon-ish. The erosional forces that created the cracks between the rocks continue to degrade the stones even today (I mean, you saw all the lichen), and in several million years the whole area will just be flat.

Nancy and I definitely enjoyed our time in the park – it was a lovely day, with highs in the low 60s and very calm breezes, and the 4-mile hike gave all of us some great views and good exercise (Monday, January 9, was a day of relaxation and recuperation for Gunther). We plan to take the Goddard to the park in the next few years for some actual camping – it has more than 40 developed sites – and it has some other trails that we haven’t yet enjoyed.

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