Big Sur Geology
The mountains of the rugged Big Sur coastline rise to 5,000 foot
summits within two miles of the ocean, the most abrupt elevation
change of the entire Pacific shore.
Several hundred million years ago, river-borne sediments from
a mountain range in what is now Mexico were deposited along the
western coast. These layers of sandstone, siltstone and limestone
were compressed and folded by the underriding of tectonic plates
at the continent's edge. The sediments metamorphosed with pressure
into schist, gneiss, granofels and marbles--now the oldest rocks
in the Santa Lucia range.
By sixty five
million years ago, this plate -- called the Salinan block -- began
to drift northward. In response to the clockwise rotation of the
Pacific Ocean's crust, the block was temporarily halted in its
smooth progress and became jostled with faulting and uplifting,
a process that still continues today. Seismic activity along the
many faults is common as the mountains continue to be uplifed.
Stream canyons frequently follow fault lines. Lateral faults are
in the majority here, hence, most canyons parallel the coast rather
than descend directly to it.
highest peaks visible are granitic rock, which tends to be more
resistant to erosion. In places where stream erosion was minor,
the taller peaks may also be marble (metamorphosed limestone)--Pico
Blanco is one such marble summit. The original sediments of sandstone
and siltstone have been tilted up into cliffs in some areas. The
sculpted shapes at Point Lobos are rare local examples of conglomerate