Standing in ranks on the lower slopes of Pueblo Canyon, rock sentinels with stone heads and conical bodies keep watch over canyon floor. A creation of an unusual combination of geology, the photogenic rock towers have lured visitors to the canyon for more than a century. Known variously as hoodoos, stone tents, or tent rocks, the formations are found only in a handful of locations around the world.

Tent rocks in Pueblo Canyon are composed of welded volcanic ash spewed from a massive eruption of the Valles Caldera about 1.2 million years ago. A mixture of pulverized rock and hot gases flowed down from the rim of the volcano like liquid, spreading a layer of fused ash—tuff—up to 200 feet thick. Subsequent rainstorms moved assorted sized chunks of lava from above and deposited them on top of the ash. A stream draining the east face of the volcano gradually carved a deepening canyon out of the deposits. In the depths of Pueblo Canyon, the erosion-resistant lava boulders offered protection to the much softer tuff layer below. As the softer material eroded away, the caprocks of lava were left balanced on columns of tuff. Where the caprock remains in place, the formation takes on the appearance of a cloaked human figure. Other caprocks gave up their precarious perch, leaving behind teepees of tuff that give the features their name.

In the first two decades of the twentieth century, the tent rocks were one of the popular tourist destinations in northern New Mexico. Visitors taking the long, rough road from Santa Fe to Bandelier National Monument often enjoyed a side trip to Otowi Pueblo and the tent rocks upstream of the site. Photos of the tents were featured in The Ethnogeography of the Tewa Indians by the Smithsonian Institution’s John Peabody Harrington. The September 1909 edition of National Geographic featured photos of Pueblo Canyon and commented on the unusual rock formations.

“At the village in Otowi Cañon the wonderful “Tent Rocks’ comprise the distinctive feature. In this vicinity there are probably fifty of these cone-shaped, porous formation of tufa, about one-half of them bearing on the pinnacle a stone of another kind. Some of the Tent Rocks were excavated by the ancient people and used as dwelling-places, the inner walls still showing the prehistoric plaster.”