About 25 miles southwest of Bodega Bay, just beyond the horizon on a clear day, a huge rocky mountain rises from the muddy ocean floor to within 120 feet of the blue Pacific surface.
The 93 million-year-old formation, once a chunk of the southern Sierra Nevada, sheared off and slowly edged along the San Andreas fault to the North Coast. It lay undiscovered until the 1850s and wasn't seen by human eyes until 1978.
But the 26-square-mile granite mass known as Cordell Bank is a smorgasbord for scores of species of seabirds and whales that fly and swim thousands of miles to feast on an abundance of food procured by the wind, the Earth's rotation and a southbound current that sweeps along the California coast.
Nutrients drawn from the ocean's frigid depths provide the base of a food chain that sustains life forms ranging from microscopic plankton to the world's largest creature, the blue whale, with a profusion of finned, feathered and furred animals in between.
On Cordell Bank's rocky ridges and pinnacles closest to the surface, a dazzling array of sponges, corals, sea squirts and sea stars are layered one on top of the other, while vast schools of groundfish swim close by.
The organisms at Cordell Bank are served by one of the world's most productive ecosystems, known as an upwelling system, that literally manufactures food and delivers it all year long.
"They just sit there and gobble as the food floats by," said John Largier, an oceanographer at the Bodega Marine Laboratory who describes the upwelling as "a perennial fountain of youth."
Bob Schmieder of Walnut Creek, who says he is the first person to see Cordell Bank through a scuba diver's mask, said "the place just grows like a Sunset magazine garden ... complicated, colorful and alive."
Cordell Bank, a place unknown to most people who aren't fishermen or scientists, is in the news because of the 529-square mile marine sanctuary that surrounds and protects it from harm, such as overfishing and energy development.
(On Google Earth, the bank is labeled and its underwater contours are visible, with depth below the surface shown wherever the cursor rests.)
When the National Oceanic and Atmospheric Administration announced plans in December to more than double the size of the Cordell Bank and adjacent Gulf of the Farallones national marine sanctuaries, North Coast environmentalists and public officials hailed it as the long-sought salvation from the threat of offshore oil drilling.
Moving the sanctuaries' boundary from Bodega Bay about 60 miles north to just beyond Point Arena in southern Mendocino County will protect the entire marine food system that makes Cordell Bank - and the area stretching south to the Farallon Islands - a natural wonder.
Less than half of the system currently is protected, and an oil spill at Point Arena - an area targeted for drilling as recently as 2009 - would ride the upwelling system south to foul rather than feed the Cordell Bank coastal region.
Such a prospect provides a "strong scientific justification" for expanding the sanctuaries to Point Arena, said Dan Howard, superintendent of the Cordell Bank National Marine Sanctuary.
Upwellings occur in thin bands along the west coast of four continents - North and South America, Europe and Africa - where wind drives what's known as a boundary current.
The upwellings cover only 5 percent of the world's oceans, but account for about one-fourth of the global fish harvest.
The California Current, which extends south from British Columbia to the tip of Baja California, provides the locomotion for the Point Arena upwelling.
Persistent north winds, strongest along the North Coast in May and June but prevailing year-round, catch the top 100 feet of the ocean's water, Largier said. The Earth's rotation contributes a force - the Coriolis effect - that pushes the water out to sea, drawing an upwelling of cold, clear water from depths up to 1,000 feet to replace it.
The upwelling carries nutrients, primarily nitrate and phosphate, that are the product of natural composting of dead organic material at depth and on the ocean floor. "As it comes to the surface, the ocean is being fertilized," Largier said.
Sunlight strikes the nutrients about 100 feet down, igniting a massive bloom of phytoplankton, microscopic plants that turn the water green, like "grass in a springtime meadow," he said.
Tiny animals, mostly copepods and krill, devour the plants, filling the ocean with a moveable feast.
The headlands at Point Arena accelerate the wind and current, the coast range of mountains channels the wind and the Point Reyes Peninsula bounces the current over Cordell Bank.
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