This can be useful for helping to describe concealed geologic structures, such as faults, granite bodies, and sedimentary basins. Two kinds of geophysical studies are underway at Fort Irwin .
Some rocks are more magnetic than others.
The rocks within a young lava flow, for example, usually have more magnetic minerals than typical sedimentary rocks. By measuring the magnetic field just above the earth, we can learn something about the contacts between such rocks based on their magnetic properties. 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.