Round Top is an extinct volcano located in the Berkeley Hills, just east of Oakland, California, within Contra Costa County.

The park was renamed Sibley Volcanic Regional Preserve in 1958 in honor of Robert Sibley, the second president of the park district, shortly after his death in 1958.

The volcanic activity that created Round Top started around 10.2 Million years ago[2] and continued for over a million years.

[3] The area has two known main volcanic vents: one under the Lawrence Berkeley National Laboratory and the other at Round Top itself.

Over time, the Round Top vent has tilted and fallen sideways, a testament to the geological changes that have shaped the region over millions of years.