Imperial Valley Region Geology

Red Hill and dried up embayment of the Salton Sea.
Red Hill and dried up embayment of the Salton Sea.

The Imperial Valley Region is a very geologically dynamic area. It covers most of the southeastern corner of California and northern Baja California in Mexico. The region is very seismically active in addition to some volcanic activity. Outside of the Cascade volcanoes in Northern California, such as Lassen Peak, this region has the most recent volcanic activity in California. These pages will discuss some of the more unique aspects of the geology in this region with photos and information on various locations where this can be seen.

Spreading Center Geology

In the area adjacent to the southeastern Salton Sea, there is a rather unique geological occurrence, at least in North America. A spreading center, the same type that exists in the East African Rift and the Mid-Atlantic Ridge, is underneath the valley. This rift, an extension of the East Pacific Rise, has been forming for the last 30 million years since the spreading center between the Farallon Plate and the Pacific Plate was overridden by the North American Plate.

As a result of this geologic collision, the area is very seismically active as well as a lot of geothermal activity. The area is also known as the Brawley Seismic Zone. This zone is an area with “stepover” faults, a transition between the San Andreas Fault Zone and the Imperial Fault. The geothermal activity is the result of magma rising through the crust, helping the plates spread apart and creating the Salton Trough that the Salton Sea and Imperial Valley occupy.

One of the major surface expressions of the spreading center are the volcanoes at the southern end of the Salton Sea. These volcanoes mark some of the most recent volcanic activity in Southern California. Red Hill, Obsidian Butte, Mullet Island all are volcanoes marking this recent activity. In addition to these volcanoes, there is also a large amount of geothermal features in the area. Extending from near Red Hill to near Bombay Beach, there are numerous boiling mud pots. These mud pots are created from the groundwater being heated by the pool of magma not far below the surface and are quite gaseous. Gases, such as carbon dioxide and hydrogen sulfide, emanate from these vents and form mud volcanoes. One of the best locations for these mud volcanoes can be found near the intersection of Davis Road and Schrimpf Road.

Mud pots in the Salton Trough.
Mud pots in the Salton Trough.
Mud Volcanoes near Schrimpf Road and Davis Road.
Mud Volcanoes near Schrimpf Road and Davis Road.

Salton Sea and Lake Cahuilla

Shoreline of Lake Cahuilla along the Santa Rosa Mountains near Desert Shores.
Shoreline of Lake Cahuilla along the Santa Rosa Mountains near Desert Shores.
Eastern shoreline of Lake Cahuilla east of Niland, CA
Eastern shoreline of Lake Cahuilla east of Niland, CA

The Salton Sea, a body of water created by a mistake, is the most recent incarnation of Lake Cahuilla. The mistake, made by the California Development Company, was to use a former Colorado River channel as their “easy made” canal. In doing so, they hastened the shift of the Colorado River from the Gulf of California to the Salton Sink. This shift, which has occurred numerous times in the past, was caused in part by larger than normal spring floods along the Colorado River. More To Come.

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