San Geronimo Ridge Road: Green Hill to Sir Francis Drake Blvd

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This out-and-back hike was a segment of the Bay Area Ridge Trail mainly along the San Geronimo Ridge between the Mt Tamalpais Watershed area of the Marin Municipal Water District and Gary Giacomini Open Space Preserve.  I started at a trailhead on Sir Francis Drake Blvd. about 2 miles west of Fairfax at the Fairfax end of Brown Bridge.  (If you reach the White Hill Summit, as I initially did, you’ve gone too far.)  The trailhead itself is just some roadside parking, with room for perhaps 6-8 cars.  There are actually two trailheads at this parking area, and it turns out that the correct one is partially obscured by some residual road construction barriers.  So I started hiking on an incorrect trail – but it really didn’t matter since it did meet up with the Bay Area Ridge Trail part way up the hillside.

The route I took went through a very shady area past beautiful, tall redwood trees and lush ferns.

image of redwood trees close to the trailhead

Redwood trees close to the trailhead

The trail climbed steeply, with a few hundred feet of elevation gain in about 0.25 mile.  About halfway up there was a Tee intersection, without signage, where I went left, and then another Tee intersection with a forest road, where I went right.  After about 0.25 mile on the forest road I found the signage indicating that the Bay Area Ridge Trail was joining the road.  On my return trip I followed the Bay Area Ridge Trail signage back to the trailhead; since the grade was more gradual, the distance was 0.4 mile longer.  Mileages below are from the trailhead using the correct trail.

GPS track

GPS track

This road is the White Hill Fire Road which passes through White Hill Open Space Preserve and climbs steadily to about 1150 feet elevation at about 2 miles from the trailhead.

Elevation profile

Elevation profile

Here there are good views east across San Pablo Bay.  In this picture the Richmond-San Rafael Bridge is at the right and Mt. Diablo, about 40 miles away, is at the left.

photo of San Pablo Bay, Richmond-San Rafael Bridge, and Mt. Diablo

San Pablo Bay, Richmond-San Rafael Bridge, and Mt. Diablo

The trail makes a “closest approach” to White Hill and gradually curves to the west, rolling slightly up and down.

picture of trail winding across open area

Trail winding across open area

Along the way there is a good view to the north, past Loma Alta to Big Rock Ridge at the far side of Lucas Valley Open Space Preserve, where there are other segments of the Bay Area Ridge Trail.

image of Lucas Valley Open Space Preserve behind Loma Alta

Lucas Valley Open Space Preserve behind Loma Alta

About 3.7 miles from the trailhead the trail tees with another fire road at a Mt. Tamalpais Watershed sign.  This is San Geronimo Ridge Road, which goes along the ridge line between the watershed and Gary Giacomini OSP.  The next 1.5 miles, along the ridge, include what I will call two false summits before the actual highest point on the trail at Green Hill (see elevation profile).  The road was rockier and the walking was more difficult than the earlier section.  Having said that, the views from the ridge were very pretty.  A distinctive hill to the northwest was visible from many locations.  I think this is Black Mountain.

photo of Black Mountain from San Geronimo Ridge Road

Black Mountain from San Geronimo Ridge Road

Around the second false summit there was an area with a forest of unusual dwarf Sargent cypress trees; the trees are of small stature due to the serpentine soil conditions.  Here is one tree, with my hiking poles propped in front of the trunk and serving as a simple length scale.  My poles are 1.1 meters (43 inches) long.

picture of dwarf Sargent cypress tree

Dwarf Sargent cypress tree

As I approached the actual summit near Green Hill, I was able to see Kent Lake, a Marin Municipal Water District reservoir formed by damming the Lagunitas Creek.  The surface of the reservoir is about 1000 feet lower than the vista point along the trail.

image of Kent Lake from San Geronimo Ridge Road near Green Hill

Kent Lake from San Geronimo Ridge Road near Green Hill

Even though I was pretty sure that this was, indeed, the actual summit, my plan was to continue to the junction with Hudt Camp Road, about 0.6 mile farther, to turn around.  After I’d uploaded my GPS data and had a chance to study the elevations, I was amused to discover that all 3 summits seem to be within less than 10 feet of the same elevation!

On the way down the hill to the junction there was a nice view of Bolinas Ridge, almost the same height as San Geronimo Ridge, across the steep valley containing Kent Lake.

picture of Bolinas Ridge from San Geronimo Ridge

Bolinas Ridge from San Geronimo Ridge

At the Hudt Camp Road junction I turned around and returned to the trailhead.  About 1.2 miles from the trailhead there was a beautiful view of Mt. Tamalpais, with late afternoon shadows spilling down the nearer hillsides.

photo of Mt Tamalpais in late afternoon

Mt Tamalpais in late afternoon

The last section of trail, which I hiked only on my return, includes a section of the former route of Sir Francis Drake Blvd, which has been rerouted to a location with less impact to the steep hillside.

As on other occasions I was pleasantly surprised by the variety of terrain and beautiful views along the trail.

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4 Responses to San Geronimo Ridge Road: Green Hill to Sir Francis Drake Blvd

  1. Pingback: A Simple Method to Quantify Hiking Effort | trailhiker

  2. Pingback: Samuel P. Taylor State Park and San Geronimo Ridge Road | trailhiker

  3. Pingback: Loma Alta Open Space Preserve | trailhiker

  4. Pingback: Samuel P. Taylor State Park and San Geronimo Ridge Road | trailhiker

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