The National Park Service (NPS) seeks additional information to better understand the source(s) of groundwater and associated groundwater flow paths to Montezuma Well (fig. 1) in Montezuma Castle National Monument, central Arizona. The source of water to Montezuma Well, a flowing sinkhole in a desert setting (see picture on cover), is poorly understood. Water emerges from the middle limestone facies of the lacustrine Verde Formation (Twenter and Metzger, 1963), but the precise origin of the water and its travel path are largely unknown (McKee and others, 1947; Lange, 1957). Some have proposed...

The April 4, 2010 (Mw7.2), El Mayor-Cucapah, Baja California, Mexico, earthquake is the strongest earthquake to shake the Salton Trough area since the 1992 (Mw7.3) Landers earthquake. Similar to the Landers event, ground-surface fracturing occurred on multiple faults in the trough. However, the 2010 event triggered surface slip on more faults in the central Salton Trough than previous earthquakes, including multiple faults in the Yuha Desert area, the southwestern section of the Salton Trough. In the central Salton Trough, surface fracturing occurred along the southern San Andreas, Coyote...

Aeromagnetic anomaly images are geophysical prospecting tools frequently used in the exploration of metalliferous minerals and hydrocarbons.

Groundwater provided public drinking-water supplies for 37 percent the population of the United States in 2000. Within the State of Florida, the reliance on groundwater for drinking water is much greater- 80 percent of the population relied on groundwater for publicity supplied drinking water in 2000.

As part of its regular program to provide timely information on domestic mineral commodities, the Bureau of Mines conducted an engineering appraisal of more than 1,300 lode and placer gold deposits in the United States to determine their gold production potential. While these deposits were estimated to contain over 400 million ounces of gold, only 9 million ounces, or slightly more than 2 percent, was found to be producible at $35 per ounce under prevailing mining and metallurgical technologies. The study revealed that any significant increase in available gold in the United States is most...

This collection of essays focuses on the Flat's first settlers: those who were on the land before the end of 1910. It describes their lives before they settled here, examines their activities during the years that they were on the land, and follows them after they left the area. It is not a standard compilation of complete life histories, however, for it concentrates heavily on the relatively short periods of time when these individuals and families were residents of Tobar Flat. It integrates biography with the area's geography and history, in essence weaving these elements into...