The Valles Caldera is the "type specimen" of a caldera complex volcano - a relatively unfamiliar type but very common through the world and through geologic history. We approached the Valles Caldera from the south, through San Diego canyon past the Jemez Springs Pueblo and the Soda Dam Hot Springs. After we entered the canyon, the walls were capped with ash-flow tuffs from the Valles caldera -- the Bandelier Tuff. Closer to the caldera itself, we passed cliffs of obsidian erupted from the caldera - the Banco Bonito lava flow. We had lunch on the caldera rim, looking across the caldera "moat" to its resurgent dome, Redondo Peak, and to several of its obsidian lava flows. The flanks of Redondo Peak host many hot springs, fumaroles, and cold acid springs (all related to the volcano), but we could not gain access. After lunch, we stopped at a road cut in the Banco Bonito obsidian flow and its underlying pumice, and then in the Valle Grande itself.
  Other stops on this field day are described in separate pages: desert crust soils, paleozoic-cretaceous rocks, and the Soda Dam hot springs and travertine deposit.