Tunnel to Marin Headlands Closed
The tunnel on Bunker Road from Alexander Avenue in Sausalito towards the Marin Headlands is closed for construction. Please follow the detour signs to Conzelman Road (just above the north end of the Golden Gate Bridge) to go up over the hill. More »
Muir Beach (but not nearby Muir Woods) parking lot closed June-November 2013
Muir Beach parking lot will be closed from June-November 2013 due to construction. Restrooms or nearby parking will not be available at Muir Beach during this period. Pacific Way is closed except to residents. Check back for updates or call (415)561-3054 More »
CAUTION: Post Storm Damage to Coastal Trail
The Presidio Coastal Trail segment just north of the Pacific Overlook and adjacent to Lincoln Blvd remains CLOSED indefinitely. We have posted signage to alert bicyclists and hikers and with information for safe trail alternatives. More »
The Story Behind Cookie Tectonics
Purpose of the activity: To provide a fun activity, using a common item, to demonstrate the geologic history of the Marin Headlands (and the SF Bay Area east of the San Andreas Fault) from approximately 180mya to about 30mya.
Geologic Concepts: Plate tectonics, plate boundaries, subduction, accretionary wedge, Franciscan Complex.
Background: It often seems that geologists use familiar food to describe rocks and landforms when mere hand-waving can’t do the job. Maybe it’s the hunger pangs we feel after tramping around landscapes better suited to mountain goats than bipeds. Whatever the reason, I still recall my geology field course outings in the early 1970s—eating bag lunches in rugged and remote mountains, commiserating with fellow students from the University of Montana. Invariably, our lunches became source material for geologic modeling. The humble PB&J sandwich could be bent and folded into tortured strata. The frosting slab of a sandwich cookie could become the Lewis Overthrust Belt. Trail mix was the stuff of a good conglomerate.
California geologists continued the edible trend. When I started my career as a park ranger in the Golden Gate National Parks in the mid-1980s, Clyde Wahrhaftig described the chaotic Franciscan Complex as a “tectonic stew,” or Jell-o salad. Today, Doris Sloan uses the phrase “melted ice cream landscape” to describe our Bay Area hills.
When I began developing ranger-led geology programs in the Marin Headlands in 1992, co-worker Diane Dobos-Bubno mentioned that she liked to use Oreo cookies for the geologic story of the Marin Headlands. After much research and field testing, I fashioned a script to accompany a sandwich-cookie demonstration to explain the formation, migration, and accretion of the Franciscan rocks onto the North American plate.
Did You Know?
The international peace symbol was designed in 1958 as the logo for the Campaign for Nuclear Disarmament (CND) and has deliberately never been copyrighted.