Hi Todd,

Here's a little background on the area:

Robert Sibley Volcanic Regional Preserve

East Bay residents have several volcanoes in their backyard at Sibley Volcanic Regional Preserve, which shares with Temescal and Tilden the distinction of being one of the District's original parks.

Round Top, a peak within Sibley and one of the highest peaks in the Oakland hills, is made up of lava and volcanic debris left over from a 10-million-year-old volcano.

Though Round Top was once the infilling of a great cauldron, it stands out today because it was originally surrounded by sedimentary rocks of the Orinda Formation, which have eroded away.

During the past 10 million years the Berkeley Hills were uplifted on a gigantic scale because of strains on the Hayward and Moraga fault systems. This uplift entailed folding of the rock formations, and the Round Top complex was tilted on its side.

This folding and erosion have exposed a cross section of a great volcano, right down to its roots, providing an unsurpassed outdoor laboratory for the study of volcanism in the Central Coast Ranges.

Volcanic dikes, mudflows, lava flows, and other evidence of the extinct volcanoes are visible throughout the park's 660 acres. There are also vistas of Mt. Diablo and the hills of Las Trampas, and beautiful displays of wildflowers in season.

An unstaffed visitor center next to the staging area at the park entrance has displays illustrating the park's geology, and a supply of park brochures containing a map with a self-guided volcanic tour.

The park is named in honor of Robert Sibley, who helped found the Park District and served 10 years on its board.

Sibley Volcanic Preserve's main entrance is on Skyline Boulevard just east of the intersection with Grizzly Peak Boulevard in the Oakland hills.

• Robert Sibley Volcanic Regional Preserve