Geological Setting
Cordell Bank was originally created 93 million years ago, as a member of the Sierra Nevada mountains. The grinding of the plates at the San Andreas Fault, with the Pacific Plate moving north and the North American Plate moving south, parts of the Sierra Mountains were sheared off and carried northwards, including Cordell Bank. Eventually this grinding carried Cordell Bank to its present location opposite Reyes Point. Cordell Bank is still moving, by an average of 3 cm (1 in) per year.
Between 20,000 and 15,000 years ago the sea level in the area was 360 ft (110 m) below the current level, leaving most of Cordell Bank exposed and making it a true island. Today the bank rises out of soft sediment, deposited on the bank more recently by coastal erosion. Within just 7 miles (11,265 m) of Cordell Bank, the continental shelf drops to over 1 mi (2 km) deep. The seamount is largely composed of granite.
Read more about this topic: Cordell Bank National Marine Sanctuary
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