The formations giving the name to this national monument (later upgraded to a national park) are made up of rhyolithic and andesitic rocks going back to an ancient volcano ripped apart by tectonic movements along the San Andreas Fault.
The formations giving the name to this national monument (later upgraded to a national park) are made up of rhyolithic and andesitic rocks going back to an ancient volcano ripped apart by tectonic movements along the San Andreas Fault.