[Robert A Cook PE]

Many years ago, before I left my duty station in the north bay area, I took my dad (long-time civil/structural engineer) on a self-created full driving tour of the entire San Andreas fault from the south finger lakes through the golden gate to the 1906 epi-center north of the bay.

It is very, very sobering to see in the roadside cuts and creek beds the twisted, crushed, stretched rock - realizing that THIS is where the earth is moving northwest - and THAT (a few steps sideways, is the earth is moving south-east (relative directions).

The rock (on the fault line) is literally no more than gravel and sand now: but whole mountains have been cut in half on that split by millions of years of forces.

[Darksheare]

Pinnacles is, if memory serves, half of a volcano.
The other half is 170 or so miles to the southeast.
I haven't seen pics of the other half of it.