Wednesday, June 27, 2012

Trails with a view of San Francisco Bay: Sibley's Volcanic and Quarry Trail

The Volcanic Trail and the Quarry Trail in the Sibley Volcanic Regional Preserve contour the rolling ridges of the Berkeley-Oakland hills. Along these trail, hikers, mountain bikers and horseback riders enjoy the view over the lower ridge forest to the Bay with Treasure Island and the skyline of San Francisco in the background.

On a foggy day this westward view may be rather limited; but perhaps not to the east, where you can see Mount Diablo. In late summer or fall you are likely to experience the hot and dry Diablo Winds coming from there. Being located close to Oakland neighborhoods, the Sibley Preserve is a wildland urban interface (WUI), also called wooei. The preserve and neighborhoods are at a high fire risk when such winds from the east blow over the ridge.

The most spectacular features are found right next to the trails— for a geologist anyway. Fires, blasts and hot lava have ruled over the area for quiet some time, evidenced by the basalt lava blocks scattered around. You are invited to explore sites that, for example, expose Orinda Formation river gravels and mudstones, brick-red knobs, basaltic tuffs and other rocks built from lava and ash.

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