During the Oligocene

Oligocene

The Oligocene is a geologic epoch of the Paleogene Period and extends from about 34 million to 23 million years before the present . As with other older geologic periods, the rock beds that define the period are well identified but the exact dates of the start and end of the period are slightly...

 epoch

Epoch (reference date)

In the fields of chronology and periodization, an epoch is an instance in time chosen as the origin of a particular era. The "epoch" then serves as a reference point from which time is measured...

, a series of caldera

Caldera

A caldera is a cauldron-like volcanic feature usually formed by the collapse of land following a volcanic eruption, such as the one at Yellowstone National Park in the US. They are sometimes confused with volcanic craters...

 building eruptions of titanic proportions, some as large as VEI-8, devastated what is now Colorado

Colorado

Colorado is a U.S. state that encompasses much of the Rocky Mountains as well as the northeastern portion of the Colorado Plateau and the western edge of the Great Plains...

 and raised up the mountain chain, part of the San Juan Mountains

San Juan Mountains

The San Juan Mountains are a high and rugged mountain range in the Rocky Mountains in southwestern Colorado. The area is highly mineralized and figured in the gold and silver mining industry of early Colorado. Major towns, all old mining camps, include Creede, Lake City, Silverton, Ouray, and...

. The La Garita supervolcano's

La Garita Caldera

La Garita Caldera is a large volcanic caldera located in the San Juan volcanic field in the San Juan Mountains near the town of Creede in southwestern Colorado, United States. It lies to the west of the town of La Garita, Colorado...

 mega-colossal eruption created 5000 km³ of tephra

Tephra

200px|thumb|right|Tephra horizons in south-central [[Iceland]]. The thick and light coloured layer at center of the photo is [[rhyolitic]] tephra from [[Hekla]]....

, the largest eruption known. The volcanic hotspot has been dormant for millions of years and is now of no danger to anyone.

Today, they are one of Colorado's lesser known, but more picturesque wilderness areas, the La Garita Wilderness

La Garita Wilderness

The La Garita Wilderness is a U.S. Wilderness Area located in the La Garita Mountains of southern Colorado. The wilderness established in 1964 in Gunnison and Rio Grande national forests includes a segment of the Colorado Trail...

 is, in fact, one of the state's original five. "La Garita means "the lookout" in Spanish, and this wilderness amply deserves the name. From the summit of this wilderness's single fourteener (14,014 foot San Luis Peak

San Luis Peak

San Luis Peak is a fourteen thousand foot peak in the San Juan Mountains of the U.S. state of Colorado. It is located in the La Garita Wilderness in Saguache County approximately north of Creede...

), climbers can gaze across the upper Rio Grande Valley

Rio Grande

The Rio Grande is a river that flows from southwestern Colorado in the United States to the Gulf of Mexico. Along the way it forms part of the Mexico – United States border. Its length varies as its course changes...

 and down the long stretch of the San Luis Valley

San Luis Valley

The San Luis Valley is an extensive alpine valley in the U.S. states of Colorado and New Mexico covering approximately and sitting at an average elevation of above sea level. The valley sits atop the Rio Grande Rift and is drained to the south by the Rio Grande River, which rises in the San Juan...

. About 35 miles of the Continental Divide

Continental Divide

The Continental Divide of the Americas, or merely the Continental Gulf of Division or Great Divide, is the name given to the principal, and largely mountainous, hydrological divide of the Americas that separates the watersheds that drain into the Pacific Ocean from those river systems that drain...

lie well above a sprawling forestland that provides ideal habitats for huge numbers of elk and mule deer.