Spirelike rock formations 500 to 1,200 feet high, with caves and a variety of volcanic features, rise above the smooth contours of the surrounding countryside. These rocks are remains of an ancient volcano. Or rather they are part of the remains, as the rest of the volcano now lies 195 miles to the southeast. Sound intriguing? Well, the story began more than 23 million years ago when a volcano formed along the San Andreas Rift Zone. As the Pacific plate and the North American plate continued their movement this caused one side of the volcano to move in one direction and the other side to go in the other.