Sometime around sixty million years ago, when the transformation began, the lighter-weight North American Plate began overriding or subducting the denser Farallon plate, and as it did, its outer edge acted as a bulldozer, scooping up great mounds of sea floor sediment: A series of north-south ridges slowly took shape, row upon row of mountainous rubble that, in the end, stretched like parallel pleats along much of California’s western edge – rendering the Coast Range in place.
The over-ridden Farallon plate pushed at great force over time in a steadily downward motion and eventually began melting. As the two plates continued being forcibly smashed together over thousands of years, the tension cracks and fissures that formed were ready releases for the molten rock below. Volcanic magma moves upward — sometimes flowing out like molasses, other times, exploding from the earth in frenzied conflagrations. In some places the magma seeped into vertical cracks and hardened as a dike or wall. In other places it made its way along horizontal fissures to form a sort of underground lake which eventually solidified as a sill.
The residual area is absolutely breathtaking: One of my three favorite places to be under any circumstances…a truly majestic and humbling sight to take in every time I go back, and every way that I turn my head while I am there…I LOVE THIS PLACE.