Shell Ridge Open Space

Shell Ridge is located in the heart of Walnut Creek, starting a short distance from the city center and continuing to Mount Diablo. It is the largest open space area of the city, and consists of a series of parallel ridges and valleys. Shell Ridge gets its name from the marine fossils left behind when the waters of the ocean that once covered it retreated. There are lots of opportunities for hiking , biking, and horseback riding along ridge tops, creek ways, and hillsides.

Shell Ridge is also home to the historic cattle ranch Borges Ranch; and Howe Homestead Park, the Associated Press’ former home and orchard James P Howe.

This walk through Shell Ridge Open Space and Diablo Foothills Regional Park creates a double loop. Along the way you can find grassy hills, single-track tracks, steep climbs, thrilling ridgetop scenery, oak trees, fire roads, meadow valleys, forested gullies, cliffs of Castle Rock and a rewarding finish along tree-lined Indian Creek. More frequent views of Walnut Creek, Alamo, and Mt Diablo, nearby.

The route is mostly open so use sunscreen and carry plenty of water. Have an eye for mountain bikes going by.

In the late Miocene epoch the ground on which you walk was laid down as sediments in a shallow sea about 12,000,000 years ago. Mount Diablo plays a role here because it was forced upward and folded the surrounding lands about five thousand thousand years ago. Because of this, the entire area around Shell Ridge was split apart, and large blocks of these sediments appeared to rise when this happened, and the edges became loose debris which was eventually washed away by small streams. If you stand on top of Shell Ridge and look down, you might be able to imagine what this terrain looked like several thousand years ago. Such inclined blocks are arranged in parallel rows.

From horizontal the tilts range from 60 to nearly 80 degrees. The ditch along the road leading to the water tank of Muir reveals several strata of rocks with very steep tilts. Mentally, move those blocks back down again and you have an uplifted sea floor level plateau. The highest point on Shell Ridge (north of Ginder Gap) is 829 feet above the current sea level and still contains several varieties of seashells that once stood in the shallow sea.