Sunset Crater is a cinder cone located north of Flagstaff in the U.S. state of Arizona. The crater is within the Sunset Crater Volcano National Monument.

Sunset Crater is the youngest in a string of volcanoes (the San Francisco volcanic field) that is related to the nearby San Francisco Peaks.

Formation

The date of the eruptions that formed the 340-meter-high cone (1,120 ft) was initially derived from tree-ring dates, suggesting the eruption began between the growing seasons of AD 1064–1065. However, more recent geologic and archaeological evidence places the eruption around AD 1085. The largest vent of the eruption, Sunset Crater itself, was the source of the Bonito and Kana-a lava flows that extended about 2.5 kilometers (1.6 mi) northwest and 9.6 kilometers (6 mi) northeast, respectively. Additional vents along a 10-kilometer-long fissure (6.2 mi) extending southeast produced small spatter ramparts and a 6.4-kilometer-long lava flow (4 mi) to the east. The Sunset Crater eruption produced a blanket of ash and lapilli covering an area of more than 2,100 square kilometers (810 sq mi) and forced the temporary abandonment of settlements of the local Sinagua people. The volcano has partially revegetated, with pines and wildflowers. The crater is the namesake for the Sunset Crater Beardtongue (Penstemon clutei). The volcano is monitored by the Yellowstone Volcano Observatory and is classified as a moderate threat.

Damage from hikers forced the National Park Service to close a trail leading to the crater, but a short trail at the base remains.

The hiking trail below the summit skirts the substantial Bonito Lava Flow. This hardened lava is black and appears fresh as it has devastated the forest in its path. The lava flow also created an ice cave or tube that is now closed to the public after a partial collapse.

2015 eruption scare

On June 5, 2015, a website with satellite images reported steam rising from the crater, leading to fears that Sunset Crater was erupting. The cause of the steam was later determined to be a forest fire, and geologists stated that the volcano was extinct.

Sunset Crater Volcano National Monument

Sunset Crater Volcano National Monument is a U.S. national monument created to protect Sunset Crater, a cinder cone within the San Francisco Volcanic Field. The monument is managed by the National Park Service in conjunction with nearby Wupatki National Monument. In 1928, a Hollywood film company, Famous Players–Lasky Corporation, planned to detonate large quantities of explosives on the side of Sunset Crater in order to create an avalanche for Zane Grey's motion picture Avalanche. Public outcry over this plan led in part to the proclamation of Sunset Crater Volcano National Monument by President Herbert Hoover in 1930.

A 1-mile (1.6 km), self-guided loop trail is located at the base of Sunset Crater, but hiking to the summit is not permitted. A trail providing access to the summit and crater was closed in 1973 because of excessive erosion caused by hikers. A visitor center is located near the park entrance, 15 miles (24 km) north of Flagstaff, Arizona, along U.S. Highway 89.

In April 2022, the Tunnel Fire burned over the entirety of the monument, though the visitor center was spared. In December 2022, 98 acres including the visitor center and administrative facilities were transferred from Coconino National Forest to the national monument.

Climate

According to the Köppen Climate Classification system, Sunset Crater has a Continental climate, abbreviated "Dsb" on climate maps.

See also

• List of national monuments of the United States