Where two continental plates meet, San Andreas fault meets the ocean. Was the closest point to epicenter of 1906 San Francisco great earthquake. Plenty of areas and paths to walk. Enjoy paragliders working the air currents too.

Mussel Rock itself is unlike other rock surrounding it. What you are seeing is the upper corner of the subducted plate that got clipped off. Imagine two thick continental plates colliding and the lighter plate is pushed below the other one. The forces keep pushing from behind and not all of the subducted can fit, eventually part of it is ripped off, the upper corner that couldn't go under with the rest of the plate and was left behind. It is no surprise that there is a major fault where two plates met. In 1906 the tension that had built up from these plates pushing on the other but for a long time there was no movement and then part of it slipped. The 'Great Earthquake' resulted from that slip. San Francisco shook and the parts that were landfill became quicksand, the buildings there disintegrated. The parts built on solid land shook, some shook apart, some remained until the fires from all the gas pipes breaking burnt it all down. And San Francisco was no more until the rebuilding began.