Round Top (elevation 1,761 feet [537 m]) is named for an extinct volcano in the Oakland Hills which started to erupt 10.2 Million years ago.

Berkeley Professor Emeritus Garniss Curtis studied the Sibley Regional Preserve extensively, dating the volcano to be 10.2 million years old.

[2] Since 10.2 million years ago, the Pacific tectonic plate has slowly pushed the volcano north.

[2] The preserve contains a Pliocene epoch volcanic center that, about ten million years ago, produced most of the lavas that underlie the East Bay ridges from Inspiration Point in Tilden Regional Park to Moraga.

The results of such compressive strains of local faults has altered the volcano's original landscape, and Round Top now tilts towards the east.

[6] Such local faults, notably Hayward and Moraga, have also caused the volcano to form a trough that is the Siesta/Gateway Valley.

"[2] A bake zone is a region where heat from the lava of the volcano changed the color of the surrounding rocks to red.

There are no picnic areas in the preserve; however, there are plenty of benches good for a rest, view and snack, as well as a campground.

The visitor center at the Skyline Boulevard entrance is unstaffed and offers brochures for self-guided tours.

Constructed in 1990 and donated as a "gift to the world" by East Bay resident Helena Mazzariello,[b] it is a favorite destination for hikers who come to pray, meditate, and examine talismans left in the center by previous visitors.

The organization reports that analysis of high-resolution aerial photographs show no trace of such activity.