La Garita Mountain (elevation 4179 m [13711 ft]), Colorado
La Garita Mountain (elevation 4179 m [13711 ft]), Colorado. The mountain is a resurgent block of Fish Canyon Tuff that is more than 1 km (0.6 mi) thick—the top is eroded and the base is not exposed. The tuff formed during the eruption of La Garita caldera about 27.8 million years ago and has a volume of more than 5000 km3 (1200 mi3)—one of the largest eruptions known on Earth. USGS photo by Peter Lipman, 1986.