Agate Beach County Park and Duxbury Reef Preserve are located in Bolinas, CA. Duxbury Reef is the largest soft shale reef in California, and one of the largest shale reefs in all of North America. Duxbury Reef is part of the Gulf of the Farallones National Marine Sanctuary, encompassing over 1,280 square miles of ocean and shoreline along the northern California coast. The sanctuary protects 33 marine mammal species, including 20% of California's breeding harbor seal population. Agate Beach covers 6.6 acres, with nearly two miles of shoreline at low tide.

Sea tunnels and bridges are carved from shale and melange outcrops on the high tide line of Agate Beach

Over 20% of California's harbor seals breed in the Gulf of the Farallones National Marine Sanctuary

A receding tide at Duxbury Reef reveals acres of tide pools

With caution, you can venture out on natural jetties to explore the low intertidal zone

Various types of algae grow in the sub-regions of the intertidal zone

Tide pools form against the bluffs over Duxbury Reef

Look for mollusks, anemone, sea stars, barnacles, and snails in the tide pools of Duxbury Reef

Exposed cliffs over Agate Beach and Duxbury Reef are particularly susceptible to erosion

A short trail leads from the parking area to Agate Beach

A natural jetty extends out into Duxbury Reef

The scalloped coast line of Agate Beach

Nearly two miles of shoreline are exposed at low tide on Agate Beach

Sunset at Agate Beach

High tides rush over and through outcrops, bridges, coves, and tunnels on Agate Beach

A turkey vulture in the bluffs over Agate Beach