Valles Caldera National Preserve - New Mexico

Valles Caldera is one of three active supervolcanoes in the United States. The other two are Yellowstone and Long Valley (in the vicinity of Mammoth Mountain and Mono Lake in California). A supervolcano is one that is very large and with the potential to have major effects on global climates and ecosystems if they were to erupt. Valles Caldera is one of the most thoroughly studied caldera complexes in the United States. It has been called the "premier example of a resurgent, structural caldera on planet earth [which...] exhibits world-class examples of landforms resulting from a very large explosive volcano..." It is a volcanic field, a cluster of many smaller volcanoes with many small centers of eruption, unlike the prototypical Hawaiian volcano which is just one volcano. However, it has had at least two explosive caldera events, the most recent about 1.2 million years ago, which formed the Valles Caldera and caused a thick ash flow, called the Bandelier Tuff, to cover almost all of the earlier volcanic rock. The Valles Caldera was not created by an eruption which blew off the summit peak. Instead, the caldera was created when the ground above the magma chamber collapsed into it during a series of explosive eruptions. 

This map of the Valles Caldera is from here. 

It is located in the Jemez Mountains of northern New Mexico, northwest of Santa Fe and has a 13.7 mile diameter (it is larger than the Ngorongoro Crater in Tanzania, which we have visited, which has a diameter between 10 and 12 miles). The floor of the caldera is 8,000 feet or higher and there are lava domes within the crater that reach as high as 11,253 feet (Redondo Peak). Cerro la Jara, a 247 foot rhyolite lava dome near the entrance station, is the most obvious lava dome to a neophyte like me, as it is surrounded by large grass areas in the caldera and has the shape and size of what I think of when I think of a lava dome. 

Looking out over the grass fields of Valle Grande. 

Cerro la Jara, a volcanic dome in Valle Grande.

The caldera contains hot springs, natural gas seeps and fumaroles, none of which we saw, and beautiful grass valleys (valles) which give it it's name. We drove in to the entrance station in Valle Grande, the largest grass valley, and continued on almost to the other side of the caldera. Valle Grande is the only grass valley accessible by (dirt) road. 

During our drive in the caldera I thought the mountains ahead were the other side of the caldera rim. However, after looking at the volcano map, I believe they are just large lava domes within the caldera. 

The caldera has a subarctic climate with very cold winters and mild summers. The average high in July, the hottest month, is 76 degrees. The average low for the same month is 38 degrees. Only two months, July and August, have an average low above freezing. 

The caldera has a herd of 2,500 to 3,000 elk. I visited the caldera twice, once with Judy in late morning where we saw none, and then early the next morning alone where I saw lots and lots of them, both in the trees on the sides of the caldera and on the caldera floor. 

Two elk partly up the rim, with the caldera floor below them. 

Elk on the caldera floor. 

We found a colony of Gunnison's prairie dogs near the Valle Grande entrance station.

We also found several birds near the entrance station, including a raven and some barn swallows, including a barn swallow nest on the entrance station. 

A poor photo of a mule dear on the caldera rim. 

I really loved the caldera and would like to explore it more someday.