"This is a complicated geological area, what with volcanic dikes, mudflows, and lava flows. A eucalyptus forest covers most of the trails in this area, which has a violent past and a calm and comforting future. The Sibley Volcanic Regional Preserve was one of three initial parks established by the East Bay Regional Park District, way back in 1936. Even farther back, about 10 million years ago, lava flowed through the area, spreading north toward Inspiration Point and southeast to Morgana. Eventually, weather eroded the hard volcanic rock, which is now open for all to see. At the unstaffed visitor center, be sure to pick up the brochure detailing a self-guided trek through this volcanic wonderland."