Sibley Volcanic Regional Preserve,
East Bay Regional Park District,

Contra Costa County

In brief:
This east bay hills loop includes a self-guided tour through ancient volcanic features, and hosts a Bay Area Ridge Trail segment.

Distance, category, and difficulty:
This 2.6 mile loop hike is easy. Trails have minimal elevation changes and the preserve is small. Trailhead elevation is around 1400 feet. The featured hike climbs to about 1600 feet, then descends back to the trailhead -- total elevation change is about 500 feet.

About half shade, half full sun.

Trail traffic:
Moderate, with lots of local foot traffic.

Trail surfaces:
Dirt fire roads and trails, and 2 short segments on pavement.

Hiking time:
1 hour.

Nice all year, but best in spring.

Getting there:
From CA 24 in Alameda County, exit Claremont (exit 3). Drive about 1.5 miles northeast on Claremont Avenue to a major intersection with Ashby. Continue straight through the light, then turn right to remain on Claremont Avenue (Claremont Boulevard veers left). You should see a brown "parks" sign for Tilden and Sibley Parks, then pass the back on the Claremont Hotel on the right. Continue on Claremont about 2 miles to the intersection with Grizzly Peak Boulevard. Turn right and drive about 2.4 miles to the intersection with Skyline Boulevard. Turn left onto Skyline, and almost immediately, after 0.1 mile, turn left into the preserve entrance.

Get driving or public transit directions from Transit and Trails:

GPS Coordinates* for Trailhead:
Latitude 3750'51.78"N
(* based on Google Earth data, shown as degrees, minutes, seconds)

Gas, food, and lodging:
Gas, restaurants, pay phone, and stores near the junction of Claremont and Ashby, about 3.5 miles to the northwest. No camping.

Trailhead details:
No entrance or parking fees. Parking for about 25 cars in two gravel lots. Be sure not to block the gate to the right of the visitor center, as utility vehicles use this paved road regularly. Restrooms and drinking water at visitor center. Detailed map and self-guided tour pamphlet available at visitor center. There is no designated handicapped parking.

Most trails are hiking and equestrian only. A few trails are multi-use. Dogs are permitted at Sibley, but are not allowed on adjacent Huckleberry trails. Park is open from 5 a.m. to 10 p.m., unless otherwise posted.

The Official Story:
EBRPD's Sibley page.
EBRPD headquarters 510-562-PARK

Map Choices:
• Use AAA's San Francisco Bay Region map to get there.
Map from EBRPD
Afoot and Afield: San Francisco Bay Area, by David Weintraub (order this book from has a great map and descriptions of a Sibley hike.
East Bay Trails, by David Weintraub, has a simple map and preserve description (order this book from
The Bay Area Ridge Trail, by Jean Rusmore(order this book from has a simple map and descriptions of Sibley's segment of the Ridge Trail.

East Bay Out, by Malcolm Margolin, has a good history of the park (order this book from
Geology Trails of Northern California, by Robin C. Johnson and Dot Lofstrom (order this book from has a nice geological description of this preserve.

Sibley in a nutshell -- a printable, text-only guide to the featured hike.

View photos from the featured hike

Go to Bay Area Hiker Home page

Sibley Volcanic Regional Preserve was one of the first three parks established by the East Bay Regional Park District. Dedicated in 1936 (!), Sibley is certainly unusual: who would guess that part of the east bay hills was volcanic? Photo of the preserve entranceThe geologic history of this area may well catch you by surprise. About 10 million years ago, lava flowed from here, spreading north to Inspiration Point and southeast to Moraga. The rock around the volcano eventually eroded, and today cross sections of the volcano are out in the open for all to see. A pamphlet available at the (unstaffed) visitor center allows you to take a self-guided volcanic hiking tour. And along the way, 2 dramatic labyrinths spark the imagination.
      Round Top, the highest point at Sibley, is distinctive in appearance, height, and location. One of the highest points in the Berkeley hills, Round Top is perched over and a little south of the Caldecott Tunnel. It lives up to its name, and once you have identified its curvaceous profile, you will be able to pick it out of the east bay hills' profile with ease.    
    Start your hike at the visitor center, where you can pick up a pamphlet with the map and self-guided tour, and interpretive displays show off the different types of rocks, plants, and animals at Sibley. A paved trail at Sibley There really is only one loop hike starting at Sibley, but this trailhead is also an important staging area for hikes to the north (about 3.5 miles to Tilden) and to the south (about 3 miles to the Skyline Gate of Redwood Regional Park). The "top" of Round Top is private and off limits, but there are great views from Round Top Loop Trail, particularly on clear winter days.
      For the featured hike, walk down the steps of the visitor center, turn left, and walk up the paved road. The right side of the multi-use road drops off to the south, and there are sweeping views past Huckleberry Preserve and Redwood Park, all the way to the mountains of eastern Santa Clara County. Along the edges of the road yellow star thistle thrives among a plant community of coyote brush, poison oak, Monterey pine, eucalyptus, California bay, coast live oak, and madrone. You might notice a few shrubs of toyon, a native plant with elliptical evergreen leaves and red berries developing in autumn and persisting through winter. Photo of Round Top Loop TrailToyon is one of 5 vines, shrubs, and trees which produce conspicuous red berries at Sibley. Look also for madrone, a tree with evergreen leaves, peeling bark, and marble-sized berries in winter, cotoneaster, a non-native shrub that puts forth small red berries in winter, hawthorn (notched leaves and small red berries in late summer and early autumn), and honeysuckle, a vine that dangles jewel-like berries in autumn. After 0.11 mile, the road splits at an unsigned junction. Stay to the right on the paved trail.
     Monterey pine, California bay, and coast live oak crowd the road. At 0.26 mile, you'll reach a signed junction with Round Top Loop Trail (you might only notice the small path to the right, but the other part of the trail heads left as well). Turn right onto narrow Round Top Loop Trail.
     The hiking and equestrian trail squeezes through a forest of Monterey pine. After a few feet, at 0.28 mile, the Bay Area Ridge Trail/Skyline Trail departs to the right, descending to Huckleberry Botanic Regional Preserve on the way to Redwood Park. View south to Mount DiabloStay to the left on Round Top Loop Trail.
      Blackberry and a few hawthorn thrive beneath the pines. The trail, open to hikers and equestrians only, is nearly level. There is a brief ascent, then a dirt spur trail from the paved road enters from the left at 0.33 mile. Keep right. Round Top Loop Trail leaves the pines behind and takes up with some eucalyptus, with an understory of blackberry, lupine, fennel, poison oak, sagebrush, coyote brush, and California coffeeberry. The trail, rocky at times, winds levelly through a forest of living and dead eucalyptus and pine. Charred stumps and fallen trees serve as evidence of a fire a few years ago. The heat from the fire opened Monterey pinecones, and there are quite a few young trees making a fresh start. LabyrinythThe eucalyptus trees on the south side of the trail seem to be dying en masse, giving this section of the hike a ghostly feel. It's the quietest part of Sibley, and through the thinning trees to the south you may see deer. Abruptly, near a cattle gate, the path ascends steeply and emerges into grassland. At 0.63 mile, a faint path heads right toward the preserve boundary -- walk a few steps to a hilltop with far reaching views. When it's clear, Mount Diablo is visible to the southeast. When I visited after a few days of rain in December, the snow-topped peaks of the Sierra were prominent on the horizon. At 0.78 mile the trail dips down to a T junction. Walk straight toward a fenced viewpoint and stop #4.
      Ten million years ago the pit just downhill was the interior of Round Top volcano. Quarry mining removed the basalt lava rocks, leaving the caldera exposed. Some time since then, a labyrinth appeared. Volcanic TrailNo one seems to know how or by whom they were constructed. Small trinkets, foreign coins, and other objects are often piled in the centers. These convoluted paths are true labyrinths, rather than mazes, and although I've never seen anyone tending them, the labyrinths are always perfectly clean and tidy. The whole thing makes me think of Spinal Tap and the song "Stonehenge," but I guess that's just my weird mind. Look just to the right of the viewpoint for a cluster of buckwheat, which produces pink blossoms in autumn. Walk back toward the previous junction and turn left to visit the labyrinth.
     The broad trail descends, with coast live oak and madrone on the right and patches of willow, sticky monkeyflower, lupine, and coyote brush on the left. After sweeping down to the quarry floor, you'll reach the large, crude labyrinth.Labyrinth This area is often flooded in wet months, when you might see some newts making their way to standing water. There are plenty of unofficial paths around, and if you are planning on exploring, take note of the steep drop-offs. When you're ready, retrace your steps back to the previous junction, at 1.17 miles. Continue north (straight) on the Volcanic Trail
      Coyote brush dominates the landscape, but you might also see bushes of lupine. At 1.31 miles, Round Top Loop Trail heads back to the trailhead, left. Continue straight on Volcanic Trail.
      Along this broad multi-use trail, views to the northwest open up, past hillsides descending through grassland to forests of eucalyptus, to Volmer Peak at Tilden Park, and if it's clear, Mount Tamalpais in Marin County. Traffic noise from CA 24 is audible. If you're taking the self-guided tour, look for the numbered posts that correspond to the pamphlet's descriptions.At 1.49 miles, you'll reach a junction near a watering trough. Stay to the right, then walk a few feet to a second junction.Returning on Volcanic Trail  Bear right (ignore another trail to the right which quickly ends at a gate) and at 1.62 miles you'll reach the second labyrinth. This one is smaller and vaguely heart-shaped, and the small bluff overlooking it is a nice, semi-secluded spot for a picnic (especially if there are no cows grazing nearby). When you are ready to continue (unless you're taking the self-guided tour, and then you're on your own), retrace your steps to the junction with Round Top Loop Trail, at 1.93 miles.
        Turn right onto Round Top Loop Trail, which sweeps around the northern flank of Round Top. The multi-use trail travels through chaparral, including some big coyote brush bushes that are lovely when in full fuzz in autumn (the nickname for this plant is fuzzy wuzzy and this is why). You might also see willow and teasel. Ascending a bit, the trail crosses through a cattle gate. At 2.33 miles, you'll reach a multi-trail junction. A paved road returns back to the trailhead, straight, and uphill to a dead-end, left. The trail to the right splits almost immediately, and both paths return to the trailhead, but in a much more intimate way (watch out for poison oak) than the road. Turn right ("to Visitor Center"), then right again. Path back to trailhead
     The trail, open to hikers and equestrians only, winds through California bay, blackberry bushes, poison oak, eucalyptus, and coyote brush. Look for dramatic displays of dangling red honeysuckle berries in autumn. The trail descends to a moist spot marked with several large currant bushes. A small interpretive site identifies the hills visible to the north, and the plants of the park. Two benches make a great spot to watch birds, large (hawks), small (hummingbirds), and every size in between. The paved path is lined with madrone, coast live oak, California bay, and Monterey pine as it returns to the trailhead. At 2.56 miles, it ends at a gate a few feet from the visitor center and parking lot.

Total distance:  2.56 miles
Last hiked:  Tuesday, December 4, 2001