Colorado Desert is a low-lying barren desert basin, about 245 feet below sea level in part. It is dominated by the Salton Sea, a relative modern consequence of Colorado River floods unleashed by irrigators between 1905 and 1907. The province is a depressed fault block between active branches of the alluvium-covered San Andreas Fault with the southern extension of the Mojave Desert on the east. It is characterized by the ancient beach lines and silt deposits of extinct Lake Cahuilla. The Imperial and Coachella valleys are agricultural oases developed with waters diverted from the lower Colorado River. Drainage from these two agricultural areas has maintained the Salton Sea for more than century.

The Mojave Desert is a broad interior region of isolated mountain ranges separated by expanses of arid plains. It has several interior enclosed drainage systems characterized by ephemeral streams and many playas. There are two important fault trends that control topography -- a prominent NW-SE trend and a secondary east-west trend (apparent alignment with Transverse Ranges is significant). The Mojave province is wedged in a sharp angle between the Garlock Fault (southern boundary Sierra Nevada) and the San Andreas Fault, where it bends east from its northwest trend. The northern boundary of the Mojave is separated from the prominent Basin and Ranges by the eastern extension of the Garlock Fault. Scattered mining operations, military bases, and transportation corridors provide a basis for local development.

The Basin and Range is the westernmost part of the Great Basin, a vast topographic region that extends eastward into Utah. The province is characterized by interior drainage systems with ephemeral streams, alkali lakes and dry playas, and the typical horst and graben structure (subparallel, fault-bounded ranges separated by down-dropped basins). Death Valley, the lowest area in the United States (280 feet below sea level at Badwater), is located in one of these grabens. Another graben, the Owens Valley, lies between the bold eastern fault scarp of the Sierra Nevada and the White and Inyo Mountains. The lonely, arid landscapes have been the focus of scattered mining camps for more than 150 years, and military activities in the latter half of the 20th century. The City of Los Angeles obtains much of its domestic water from the Owens River.

Collections of unique aerial panoramas of these regions may be seen in the
Salton Basin, Mojave Desert, and Basin and Range sections of the California Atlas of Panoramic Aerial Images.