Round Top
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Round Top is an extinct volcano (elevation 1,763 feet / 537m, 122.193°W, 37.85°N) in the Berkeley Hills, just east of Oakland, California. The peak lies entirely within the bounds of Contra Costa County. In 1936, the area surrounding the peak was established as Round Top Regional Park, one of the first three parks of the East Bay Regional Parks District (EBRPD). The park was re-named Sibley Volcanic Regional Preserve for the second president of the EBRPD, Robert Sibley, shortly after his death.
Robert Sibley Volcanic Regional Preserve contains a volcanic center that, about 10 million years ago, produced most of the lavas that underlie the East Bay ridges from Inspiration Point in Tilden Regional Park to Moraga; geologists refer to this local volcanism as the Moraga Volcanics. Subsequent compressive strains produced by various local faults including the Hayward Fault folded the lava-bearing rock formations, tilting the Round Top vent complex on its side. Folding, erosion, and a quarry operation exposed a cross section of the great volcano, providing an excellent means to study a Central Coast range volcano. Lava within the vent has been dated at UC Berkeley at 9.5 million years old.
