Tomales Bay

Tomales Bay exists as a feature of the San Andreas fault. Here two huge plates of the earth’s crust move against each other, the Pacific plate west of the bay and the North American plate to the east. The crack in the earth’s surface between the plates sinks in some locations, forming what geologists call a rift valley. Tomales Bay is a flooded rift valley, the deepest part of a valley that continues south for ten more miles to return to the ocean at Bolinas Lagoon. In the San Francisco earthquake of 1906, the greatest movement occurred in this lightly populated area, moving Point Reyes north as much as 16 feet in one dramatic shift.

Tomales Bay is sandy bottomed and shallow, although the main channel depth ranges to 60 feet. The bay, 13 miles long by one-half to one-and-a-half miles wide, nestles in a dramatic setting with the high hills of Tomales Point and Inverness Ridge rising abruptly on the west, and the more gradual rise of Bolinas Ridge to the east punctuated by numerous points and bays along the bayshore. Jewel-like, placid whitesand pocket beaches dot the western shore. Both Point Reyes National Seashore and Tomales Bay State Park encompass much of the shoreline.

The name Tomales probably originated from the Coast Miwok tribe’s name for bay, tamal. Some say it’s from the Coast Miwok word for westerner. The bay’s eastern shore was well populated with Coast Miwok villages, the westernmost settlements of the Tamal Miwok who lived primarily near the western shore of northern San Francisco Bay. Still others claim the Mexican food tamales as the source.

The many piles of discarded shells, called middens, left by the Coast Miwok at villages along the bayshore attest to its abundant marine life. More than 1000 species of worms, clams, crabs and other invertebrates inhabit the bay. Fish include perch, flounder, sting rays, leopard sharks, sand dabs and herring. Almost /00 species of water associated birds have been identified here. Harbor seals also frequent the bay and the ocean just outside the bay is a major breeding area for great white sharks.

Today Tomales Bay is popular for boating, fishing, and clamming. Clams are harvested on the sand flats during low tides. Rock crabs and Dungeness crabs are netted off the bottom from skiffs. Commercial uses include robust oyster growing operations in the bay’s clean water and herring netted for their prized roe which is shipped to Japan.

Marin County residents consider conservation of Tomales Bay very important. Bay waters are nearly pristine, while the few towns are small. The ranch lands east of the bay, although ringed by considerable public land, have been dogged by proposals for developments and dumps. The U.S. Congress is considering establishing a buffer zone from the bayfront to the ridgeline which would encourage ranchers to sell development rights, allowing them to continue owning the land while including it in Point Reyes National Seashore. If the owner eventually became a willing seller, the federal government would purchase the land for the park. We hope with time that everyone will see the wisdom of preserving this national treasure.