Draft: Should be completed by early February 2025.
About our hike
Rocks we will see in this area include sandstone, radiolarian chert, greenstone, and pillow basalt.
This hike is adapted on Ted Konigsmark’s Geological Trips: San Francisco and the Bay Area, Trip 2. We start at Rodeo Beach, where this is a nice outcropping of sandstone, then head across the beach to see some pillow basalts. Then the uphill begins: We walk a couple miles and 820 feet up to Battery 129, where we can see hawks soaring (Hawk Hill) and millions of year old radiolarian chert. After a brief lunch break, we start back down and swing by the pillow basalts at Point Bonita lighthouse. Then a short hike back to the beach.
The hike is 7-8 miles, with about 1,000 feet of elevation gain.
Geology
Sandstone at north end of Rodeo Beach
.
Pillow basalts at south end of Rodeo Beach
.
Radiolarian chert at Battery 129

Radiolaria are microscopic, silica based skeletons. Radiolaria live in deep oceans, and their skeletons float down to the ocean deeps over millions of years.
Links for more information
- Hawk Hill: Golden Gate Raptor Observatory
- Alltrails map of the hike here.
- Geology of the Golden Gate Headlands. Excellent field trip guide with details of many stops.
- Geological Outings Around the Bay: Marin Headlands, 2011, KQED Quest