The largest composite volcano in northern Arizona. The summit of San Francisco Mountain once stood above 16,000 feet. The east flank collapsed in the late Pleistocene in a massive debris avalanche that reduced the summit peak to ~12,600 feet. Structurally, the cone comprises alternating lava flows and tephra shot through with dikes and cryptodomes.
Dick Holm (NAU retired) published a great geologic map of the Peaks that can be downloaded at https://pubs.er.usgs.gov/publication/i1663 .
View from northeast to southwest. Photo by Ted Grussing, Oct. 2018.
