Such maps show areas with unusually high or unusually low magnetic fields. At Fort Irwin, magnetic anomaly maps are particularly useful for learning about faults and plutons that underlie the area. Note, for example, the different patterns of anomalies to the north and south of the Coyote Canyon fault. By carefully studying these patterns, we can learn about the dip and extent of the Coyote Canyon fault beneath the earth's suface. Both the gabbro and skarn have many iron minerals that contribute to the magnetic anomaly here.
Gravity studies Rocks also have variable densities.
For example, a volume of unconsolidated sedimentary deposits has less mass andproduces a smaller gravitational attraction than the same volume of limestone or dolomite. Sedimentary basins, therefore, are often reflected in the earth's gravity field as regions of relatively low gravitational attraction. These highs and lows are very small, on the order of 0.001 percent of the earth's gravity field. This map shows the regional gravity at Fort Irwin and surrounding areas. The three hatched areas, on the other hand, indicate actual basins at Fort Irwin.