Sibley Volcanic Regional Preserve

The residents of East Bay have a volcano in their backyard in the Sibley Volcanic Regional Reserve. Sibley holds the distinction of being one of the first parks in the East Bay Regional Park District with Temescal and Tilden which was initially named Round Top Park. Later, the preserve was named in honor of Robert Sibley, who helped found the District and served on its board of directors for 10 years.

The most prominent feature of the preservation is the Round Top (1763 ft. above sea level). The unstaffed visitor center in the scene of the Skyline Boulevard displays the geology of the reserve. On the site, a self-directed booklet displays the geological characteristics of the preserve.

The preserve includes a volcanic core from the Pliocene epoch that created much of the lava flows from the Tilden Regional Park to Moraga Ridges, around 10 million years ago. Geologists call this local volcanism the Moraga Volcanics. The lava-bearing rock formations were eventually folded into compressive strains created by a variety of local failures including the Hayward Fault and the Round Top wind complex was tilted. Folding, erosion and quarry exposure offered an excellent way of researching the California Coast Ranges volcano, via the cross section of the large volcano. UC Berkeley dates lava inside the vent at the age of 9.5 million years.

Various trails allow access all over the preserve. The 31-mile East Bay Skyline National Recreation Trail, part of the Bay Area Ridge Trail, crosses the rim of Wildcat Canyon and Anthony Chabot Parks. Round Top Road goes from the visitor center of Sibley to the top of the Round Top. Round Top Loop Trail circles the highest elevation of the Round Top.

Once a quarry path, Volcanic Trail includes most of the stops on the self-guided volcanic tour. The paved Quarry Road rises and reaches the eastern end of the Volcanic Trail on the northwest side of the park. Quarry Trail connects the center of the Volcanic Trail to the lower point of Quarry Road. Finally, the Pond Trail is a short section of trail which descends to the north side of the preserve to a few lakes.

Most of the trails are hiking and horseback riding. There are a few trails that are multi-use. Dogs are not allowed on the nearby Huckleberry Trails but are allowed at Sibley. A visitor center in the park’s booklets automatically allow visitors to stroll around the park and learn about it at their leisure.

Bicycles on narrow-gage trails are not permitted, except on the Skyline Trail between the Sibley Visitor Center and Old Tunnel Lane. Bikes are allowed from the fork 15 kilometers east of the visitor center at the top of the Round Top on the broader fire paths and paved roads.