This seep also releases on the order of 100 to 150 barrels (16 to 24 m3) of liquid petroleum per day. The field produces about 9 cubic meters of natural gas per barrel of petroleum.
Leakage from the natural seeps near Platform Holly, the production platform for the South Ellwood Offshore oilfield, has decreased substantially, probably from the decrease in reservoir pressure due to the oil and gas produced at the platform.
Platform Holly & oil slick in water, February 2016. Doc Searls, the photographer, said this was more oil than he is used to seeing. Oil slicks increase after earthquakes.
Tar balls at the beach, Coal Oil Point, looking WNW. This was an unusually heavy accumulation, in June 2003. Inset shows oily sheen from fresh tar balls.
Written records, dating from as early as 1792, describe effects of offshore seeps in the Santa Barbara Channel. Oil and tar "slicks" have long been a trademark of the area. In 1792, Captain Cook's navigator George Vancouver recorded on passing through the Channel (Imray, 1868):
The surface of the sea, which was perfectly smooth and tranquil, was covered with a thick, slimy substance, which when separated or disturbed by a little agitation, became very luminous, whilst the light breeze, which came principally from the shore, brought with it a strong smell of tar, or some such resinous substance. 
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