California's geography has been shaped by volcanic activity and plate tectonics, with glaciers and erosion playing supporting roles. Many of the state's most memorable and unique landmarks tell the story of this volcanic past.

In this part of California, lava flows filled the channel of the Stanislaus River about 9 million years ago and has remained solid as the surrounding rock eroded. The result is the Table Mountain formation that stretches from Knight's Ferry beyond Sonora along Highway 108. A moderate three-mile trek to the top of this formation starts at the end of Shell Road in Jamestown and takes hikers to the amazingly flat top. To avoid the heat, try it in the spring or fall.