Kasha-Katuwe Tent Rocks National Monument (New Mexico) - The area owes its remarkable geology to layers of volcanic rock and ash deposited by pyroclastic flow from a volcanic explosion within the Jemez Volcanic Field that occurred 6 to 7 million years ago. Over time, weathering and erosion of these layers has created canyons and tent rocks. The tent rocks themselves are cones of soft pumice and tuff beneath harder caprocks.
The Jemez Mountains are a classic example of intracontinental volcanism and consist of a broadly circular ridge surrounding the famous Valles Caldera. The most recent known eruption was a basalt flow dated to 50,000 to 60,000 years before the present; however, most of the volume of the range is composed of rhyolite. The two most recent caldera-forming eruptions, dated to about 1.4 million and 1.1 million years ago, produced massive ignimbrite deposits. Soda Damn