Geological Survey Water-Supply Paper 1475-J Ground Water in the Wupatki and Sunset Crater National Monuments, Coconino County, Arizona

LANDFORMS

The Wupatki-Sunset Crater area is in the eastern part of the San Francisco volcanic field, northeast of San Francisco Mountain, the highest point in Arizona. The area is on the southwest flank of the Black Mesa basin and the regional dip of the rocks averages between 1° and 3° NE. Physiographically, it is partly in the valley of the Little Colorado River and partly on the San Francisco Plateau. The slope of the plateau is to the northeast, and locally it is accentuated by the Black Point segment of the East Kaibab monocline. In the vicinity of the Wupatki National Monument, the Black Point segment of the East Kaibab monocline separates the lower tableland from Antelope Prairie, the northeastern part of the San Francisco Plateau. The surface of the lower tableland is carved from the Moenkopi formation near the Little Colorado River. Antelope Prairie is a stripped surface eroded on the Kaibab limestone. Many of the low mesas near Wupatki Ruin are capped by thin basalt flows.

The southern part of the area, near the Sunset Crater National Monument, is in a rugged and irregular terrain that flanks the east slopes of San Francisco Mountain and includes groups of dissected extinct volcanoes consisting of numerous cinder cones and associated flows. Deposition of alluvial material in the basins between many of the extinct volcanoes has formed parks. West of O'Leary Peak, along U.S. Highway 89, glacial outwash from San Francisco Mountain forms small, rounded valleys and ridges, which contrast with the surrounding volcanic terrane.

The altitudes range from about 7,000 feet in the Sunset Crater area to about 5,000 feet in the Wupatki area. The highest point within the mapped area (pl. 20) is O'Leary Peak, which has an altitude of 8,925 feet. The lowest altitude is about 4,200 feet, at the Little Colorado River where it leaves the mapped area.

DRAINAGE

The area is drained by the Little Colorado River and its tributaries; the largest in the area being Deadman Wash. All the streams in the area are intermittent. Channels as deep as 150 feet have been eroded where the streams have breached the East Kaibab monocline in the Wupatki area. In some places the channels are choked by windblown cinders and small alluvial fans, indicating that they may have been dry for several years. Several small basins, of interior drainage due to damming by volcanic rocks, have developed near Sunset Crater. These include parts of Bonito, Black Bill, and Doney Parks.

CLIMATE

Climatological data for the Wupatki-Sunset Crater area were obtained from official records of the U.S. Weather Bureau and from records of the National Park Service. Precipitation ranges from more than 25 inches per year in the Sunset Crater area to less than 10 inches per year in the Wupatki area. For the most part, the precipitation occurs as torrential summer rainfall and winter snowfall. At Wupatki, the mean annual temperature is about 57 °F. A mean annual temperature of about 45 °F. is estimated for the Sunset Crater area, on the basis of Weather Bureau data for Flagstaff, which is at a slightly lower altitude. The difference in climate at Sunset Crater and Wupatki National Monuments is due primarily to the difference in altitude.