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Valles Caldera
In the Jemez Mountain region of New Mexico, an unusually forceful volcanic eruption created the 13-mile wide circular depression now known as the Valles Caldera, a preserve known for its huge mountain meadows, abundant wildlife, and meandering streams. The area also preserves the homeland of ancestral native peoples and embraces a rich ranching history.

The Eruption
The Valles caldera-forming eruption occurred approximately 1.25 million years ago when huge volumes of Bandelier tuff were explosively evacuated from a underground magma storage region. As a result of the "supereruption," the ground subsided along a network of nearly circular faults, called a ring fracture, leaving the caldera, a 20 x 23 km (12 x 14 mi) depression. Resurgent doming of the central caldera floor occurred between 1.25 and 1.22 million years ago, which was immediately followed by additional dome eruptions around the caldera margins up until about 40,000 years ago. These resurgent and ring-fracture eruptions are interlayered with lake deposits, indicating the caldera has been at least partially filled by lakes since its formation. The youngest volcanism occurred in the southwest sector, which coincides with the present-day Valles geothermal system, which is fueled by a magma storage region residing beneath the southwestern caldera.