Streaks come from flow in solid rock which occurred under intense squeezing in the subduction zone . This is metamorphic foliation, so called because of the layers formed during flow by the flat or platy minerals that line up parallel to flow. The ridge to the left of the trail is light green clay with dark green fragments of shiny serpentine embedded in it. Serpentine forms when very iron-rich rocks of the mantle combine with hot water. These fluids change olivene to serpentine.
Slick surfaces are polish formed by shear in fault zones.
Serpentine is intimately associated with high-grade metamorphic rocks, and may act to carry blocks of blueschist and eclogite from deep in the subduction zone up into the melange. Recent seismic studies of the Coast Ranges show another plate at depth which could be the hidden source of metamorphic blocks. The trail skirts a steep slope down to a gully with boulders scattered about. The north slope is light green serpentine, a continuation of the ridge next to the first outcrops. The boulders in the creek bed and on the beach are resistant blocks that have weathered out of the melange matrix.