The Pacific Crest Trail from this starting point climbs up and over the slope of Mount Williamson before arriving at Islip Saddle. Because there was no traffic on the highway, we chose to walk on the highway through two tunnels that went under Mount Williamson, thus saving ourselves a lot of extra up and down distance. Note the complexity of the relationships between gneiss, diorite, and granite on the face of the mountain.

Return to the San Gabriel Mountains GeoTrek Day 7 page.