The Channel Islands are located within a unique geological region off the southern California coast. Over millions of years, large plates of the earth’s crust moved along fault lines, pushing against the coastline of Mexico and California and creating the coastal geography that is seen today.
During this shifting, part of the southern California coast was rotated, resulting in the unusual east-west axis of the California coast just south of Point Conception, termed the Transverse Ranges, and the formation of the Channel Island chain along this coast. The Continental Borderland is the offshore section of the underwater geology that forms a wide continental shelf (Norris and Webb 1990). Unlike most wide continental shelves that consist of gently sloping platforms interrupted by low banks and occasional canyons, the Continental Borderland is a region of basins and elevated ridges (Norris and Webb 1990) (Fig 1). The Channel Islands are the portions of the ridges that rise above sea level.
Parallel to and situated between the California coast and the Channel Islands is the 1,950-foot deep Santa Barbara Basin. The seaward edge of the Continental Borderland (known as the Patton Escarpment) descends 13,200 feet to the deep ocean floor (Norris and Webb 1990). The highest point in the Channel Islands is the 2,450 foot Picacho Diablo on Santa Cruz Island and the deepest point within sanctuary boundaries is 5570 feet on the south side of Santa Cruz Island.
Oil and Natural Gas
More than 20 oil fields and several natural gas fields lie beneath the Santa Barbara Channel. Most are close to the mainland and several are accessed from offshore oil and gas platforms (Norris and Webb 1990). There are more than 40 naturally occurring oil and gas seeps in the Santa Barbara Channel (Norris and Webb 1990). The area is known to have one of the highest natural oil seepage rates in the world. Seeps at Coal Oil Point near Santa Barbara are estimated to discharge approximately 150-170 barrels (6,300-7,140 gallons) of oil per day (Hornafius et al. 1999).
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