Arizona
The relatively recent eruption of Sunset Crater Volcano, in AD 1085, left a classic round cinder cone.
En route to Flagstaff, Arizona, you might fly over the San Francisco Volcanic Field and the Sunset Crater Volcano. Look for the white-capped San Francisco Peaks, which host a ski resort you may be able to see in the winter, and the round black cinder cone of Sunset Crater Volcano to the east.
In the last 6 million years, more than 600 volcanoes have sprung up in the San Francisco Volcanic Field, covering 1800 square miles on the southern edge of the Colorado Plateau in northern Arizona. This area includes the San Francisco Peaks—the remains of an eroded stratovolcano similar to the Cascade Volcanoes—and Humphrey’s Peak, Arizona’s highest point at 12,633 feet. The most recent eruptions occurred around AD 1085 at the Sunset Crater Volcano—the youngest volcano in the complex.
After the AD 1085 eruption of the Sunset Crater Volcano, the Sinagua people moved to the Wupatki Pueblo, fifteen miles northeast of the crater. Ruins of the pueblo remain and can be visited.
When Sunset Crater Volcano last erupted, the area was inhabited by the Sinagua people, agriculturalists who lived in pit houses and, later, multi-roomed pueblos. The Sinagua people almost certainly witnessed the eruption, as it would have been hard to miss: the main cinder cone of the volcano was created in a matter of days (according to tree ring and paleomagnetic data), rising 1120 feet above the surrounding landscape. The blast may have been accompanied by earthquakes and exploding volcanic fire bombs, as well as ash, cinders, and lava flows a hundred feet thick.
Lava flows emanated from the cinder cones and from several long fissures that opened at the base of the volcano. From the air, these flows stand out black against the landscape, extending for four miles outward from the raised cinder cone, in the direction of the prevailing winds at the time of the eruption.
The San Francisco Volcanic Field has now been dormant for longer than 800 years, but it’s not extinct. Another eruption could birth another cinder cone in the next few hundred years. For now, a seismograph installed at the Sunset Crater National Monument visitor center keeps tabs on earthquake activity that might foretell another eruption. When it happens, we—like the Sinagua people—will have to get out of the way.
Archaeological studies of the region show that in the aftermath of the Sunset Crater eruption, the Sinagua people moved to the Wupatki Pueblo, north and east of the crater. The population of Wupatki and the surrounding area is estimated to have been around a hundred people before the eruption and as many as 2000 after the eruption. The pueblo was supported by cultivated corn and squash, and the Sinagua appear to have collected rainwater for drinking, as few springs are found in the region’s loose volcanic soils. By AD 1225 the pueblo was abandoned, likely as a result of prolonged drought.
Sunset Crater Volcano’s black cinder cone is one of many volcanic features in the San Francisco Volcanic Field.
The black cinder cone of Sunset Crater Volcano can be seen from above, flying over the San Francisco Volcanic Field in northern Arizona. Look for the San Francisco Peaks nearby, which are snowy in winter.
