Sunset Crater, a cinder cone north of Flagstaff in the San Francisco volcanic field, is the chain’s youngest volcano. Formed by a major eruption around AD 1085, it sent lava, ash, and lapilli across a wide area, with Sunset Crater as the largest vent and additional vents opening along a nearby fissure. The eruption temporarily forced Sinagua settlements to be abandoned, reshaping both landscape and human life. Later protected after public opposition to a 1928 proposal to blast part of the volcano for a film scene, the area became a national monument in 1930. The volcano is now considered extinct and access is limited to protect its fragile cinders.