Field Locations
Southern California Geologic History
During the last 150 million years, Southern California has undergone vast geological land sculpturing. Volcanoes, earthquakes, landslides, weathering, and tectonic movement have all contributed to the present day face of Southern California. This site will walk you through a few of the geologic timestamps that are beautifully carved into the coastal and desert regions of Southern California.
The early times of the Cretaceous period, 150 to 65 million years ago were turbulent times for southern California, as the Farallon plate was subducting underneath the North American plate, and volcanoes scorched the California interior. This was a period of mountain building and land reshaping. Much of present day California was submerged in the Pacific, teaming with crustaceans, and invertebrates which would eventually help form the bioclastic portions of the coastal sedimentary beds.
Some 75 million years ago, San Diego was submerged in the ocean; heavy tides swept the sandy floor throughout the region depositing beds of sand that would later become a time marker for the sedimentary bedrock. As the ocean waters began to subside, and reveal the ever now so popular San Diego coastline, the once coastal ocean community of marine animals laid rest a final chapter in the coastal diary. (Abbott, 1999)
Further inland near the Colorado River, erosional sedimentation was sealing the fate for the Gulf of California as the ever increasing flow of fine grained soil was being deposited, and would begin to separate the Salton Trough from its oceanic cousin, the Gulf of California. The deposition left by the flowing waters of the Colorado River partitioned the Gulf of California from the current San Diego/Imperial desert regions.
In the wake of this regional segregation, are fossilized records dating back to the Miocene age. This is very fortunate for geologist, as this assemblage of fauna provides a great deal of information about San Diego’s geological past in terms of the biosphere, hydrosphere, and lithosphere. Though the oceans, and the Colorado River played a key role in Southern California’s land shaping, heavy rains, and flooding have also contributed to large canyons, valleys, and troughs throughout the region.
Considerable mass wasting has formed the alluvial fans found throughout the Imperial valleys. Much of the desert plains are a result of massive flooding removing tons of debris in its path. In harmony with these processes were volcanoes, further contributing to the mountain building of the peninsular ranges, and the desert rim. Lava flows are evident throughout these areas, and a perfect example can be seen in the Carrizo Badlands. (Remeika and Lindsay, 1992)
Join with me now as we venture from the marvelously sculpted terraces of the San Diego coastline to the alluvial canyons of the Salton Trough, and deserts, where we will travel back into geological time, and picture a once thriving community of marine life and terrestrial creatures.
Begin the Tour |
