The hills near McKittrick, in the southwest corner of California's Central Valley, host the state's largest area of oil seeps. A marker at the intersection of highways 58 and 33 is about 200 meters east of the site of these photos. The thick crude in this oil seep is better described as asphalt.
Asphalt is so common in the built environment that it takes an effort to recognize this oil seep as natural. The Central Valley oil district began here in the 1860s when Anglo entrepreneurs displaced the local tribes, who used the asphalt for waterproofing and medicine. Besides oilmen, paleontologists exploited this oil seep when bones in the asphalt pools were found to be Pleistocene fossils like those in the tar pits of Rancho La Brea farther south. Today California ranks fourth in the nation in petroleum production, behind Alaska, Texas and Louisiana. But the oil seeps, extending several kilometers in these foothills, now lie mostly undisturbed.
Images 1-12 of 12
 Seep Sign |  Trickling Asphalt |  Asphalt Droplets |  Asphalt Puddle |
 Asphalt Flow |  Asphalt Crust |  Asphalt Hand Specimen |  Asphalt Specimen |
 McKittrick Siltstone |  Oil-Soaked Strata |  Asphalt Cascade |  Asphalt Streambed |
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