San Francisco volcanic field

For other uses, see San Francisco (disambiguation).

The San Francisco volcanic field is an area of volcanoes in northern Arizona, north of Flagstaff, US. The field covers 1,800 square miles (4,700 km²) of the southern boundary of the Colorado Plateau. The field contains 600 volcanoes ranging in age from nearly 6 million years old to less than 1,000 years (Miocene to Holocene), of which Sunset Crater is the youngest.^[1] The highest peak in the field is Humphreys Peak, at Flagstaff's northern perimeter: the peak is Arizona's highest at 12,633 feet (3,851.5 m) and is a part of the San Francisco Peaks, an active^[2] stratovolcano complex.

USGS Digital elevation model of the San Francisco volcanic field

Satellite image of part of the San Francisco volcanic field, presented as a 3D terrain model. Note that North is to the right.

Description

This volcanic field seems to have formed from a geological hotspot.^[3] As the North American Plate moves over the spot, new volcanoes appear. Thus, the newest volcanoes are at the east side of the field. Most of the volcanoes are basalt cinder cones, but there are also large lava domes consisting of rhyolite and dacite.

Given that Sunset Crater is such a young volcanic feature of this area and that eruptions have occurred every several thousands of years in frequency, it is likely that there will be a future eruption in the San Francisco Volcanic field.^[3] However, it is impossible to predict when and exactly where a new eruption might occur. The United States Geological Survey (USGS) says that a future eruption would likely be in the eastern side of the volcanic field, where the most recent volcanic activity has occurred. Such an eruption is likely to be small and pose little hazard due to the remoteness of the area.^[3]

Visitation and usage

SP Crater is a cinder cone with a basalt lava flow that extends for 4 miles (6 km).

Popular tourist and hiking destinations in the volcanic field include the Kendrick Mountain Wilderness, 20 miles northwest of Flagstaff; and Sunset Crater. Sunset crater has a hiking trail along an ʻaʻā lava flow to its base.^[4]

Areas of the volcanic field have been used by NASA for testing techniques for exploration in a simulated extraterrestrial terrain environment.^[5] NASA has also conducted the Desert Research and Technology Studies (DRATS) tests here.

Notable vents

Black Point lava flow in the San Francisco volcanic field. Little Colorado River at lower right. Astronaut photo from the International Space Station, 2009.

Name	Elevation		Location	Last eruption
	meters	feet	Coordinates
Bill Williams Mountain[6]	2,821	9,256	-	2.8 million years ago
Colton Crater (Crater 160)[7]	2,246	7,368	35°32′42″N 111°38′10″W	-
Double Crater[8]	2,426	7,959	35°20′44″N 111°27′5″W	-
Kendrick Peak[6]	3,175	10,418	-	1.4 million years ago
Merriam Crater	2,077	6,813	35°20′19″N 111°17′11″W	20,000 years ago
Mount Elden	2,835	9,300	35°20′47″N 111°40′40″W	-
O'Leary Peak[6]	2,718	8,916	35°24′05″N 111°31′36″W	Pleistocene
San Francisco Peaks	3,851	12,633	35°20′47″N 111°40′40″W	-
Sitgreaves Mountain[6]	-	-	-	1.9 million years ago
SP Crater (SP Mountain)[9]	2,140	7,021	35°34′56″N 111°37′55″W	5,500 years ago [10]
Strawberry Crater			35°26′38″N 111°28′40″W	-
Sunset Crater[6][11]	2,446	8,026	35°21′51″N 111°30′11″W	950 ± 40 years
Sugarloaf Peak[6]	-	-	-	220,000 years ago

See also

• List of volcanoes in the United States
• List of volcanic fields