This post will start with the geology. I'm not a geologist but as a native Californian I know something of earthquakes. Pinnacles lies on the San Andreas Fault. The rock formations are the remains of an ancient volcano that straddled the fault. The rest of the volcano is nearly 200 miles to the southeast. This part is slowly sliding north.
This view is take from the highway on the east side of the monument. The campground is on the east side and while you can hike to the west no road crosses the monument. It would take at least an hour and a half to drive to the west entrance.