Dotsero

Dotsero is a 700-meter (2,300 ft) wide by 400-meter (1,300 ft) deep maar volcano located in Dotsero, Colorado near the junction of the Colorado River and the Eagle River. It is classified as a scoria cone with evaporitic rock, basaltic tephra, and oxidized sandstone. Erupting approximately 4200 years ago, it is the youngest volcano in Colorado.