About us
This group's goal is to get exercise while exploring and learning about the geology and natural science of the San Francisco Bay Area. The aim is the mid-point between the hiking groups that don't stop long enough to explore and learn about what they're passing and the nature groups that see lots of great stuff, but don't get that much exercise.
Hikes will be lead by members with knowledge of unique, exotic, or otherwise fascinating features of our area. If you have a favorite hike that you'd like to lead, drop a suggestion and I'll make you a leader (you just have to commit to coming on the hike and sharing your knowledge).
Everyone with interest is invited, and presentations should be aimed at people with interest but not necessarily a strong academic background in the subject (although some conversations occasionally get pretty deep).
Our primary focus will be on geology, but we won't pass up a good tidbit of information about the flora and fauna as we hike.
I've finally started putting together a website with more details on the geology of our hikes. You can find them at https://geology.trampleasure.net/ A few direct links to pages on my site include:
Upcoming events
2
SF Sutro Baths/Lands End/China Beach 5 miles ~800 feet climbing
Lands End Trailhead, 24 Merrie Way, San Francisco, CA, USThis hike visits many of the points in Trip 1 of Ted Konigsmark’s Geological Trips: San Francisco and the Bay Area. Here's an AllTrails map of the hike. [This is the rescheduled hike from the April 12 rain-cancelled hike.]
Along this route, we’ll see several representative features of the Franciscan Complex, a group of rocks formed when pieces of the Farallon Plate were scraped off during subduction roughly 80–150 million years ago. The trail gives us a chance to observe how these materials were deformed, uplifted, and exposed along the coastline.
As we start near Sutro Baths and continue along Lands End, we’ll see graywacke sandstone, shale, and blocks of metamorphosed oceanic crust such as greenstone and blueschist. These rocks often appear mixed together in a chaotic arrangement known as a mélange, which reflects the shearing and pressure that occurred deep within the subduction zone. We’ll also pass a clear example of a landslide surface within the City College mélange, where the disrupted, clay‑rich material makes the slope especially prone to movement.
Farther along the trail, we’ll come across outcrops of radiolarian chert, identifiable by its thin, ribbon‑like layers of red and brown. This rock formed from the silica shells of microscopic plankton that settled on the deep ocean floor. The folding and tilting of these layers show how tectonic forces later acted on them.
As we approach China Beach, we’ll see more serpentinite and greenstone. Serpentinite forms when ultramafic rocks from the Earth’s mantle are chemically altered by seawater. Its greenish color and smooth texture make it easy to recognize, and its tendency to break down contributes to the unstable slopes in this part of the coastline.
Overall, we’ll be walking through a compact cross‑section of the Franciscan Complex, observing how subduction, metamorphism, landsliding, and uplift have shaped this stretch of the San Francisco shoreline. It’s a good opportunity to see a variety of rock types and geologic structures in a relatively short distance.
Our pace will be moderate, with plenty of stops to look at the geology, and no one left behind. We seem to average around 2MPH (including stops), so the hike should take three to four hours. Last time we took about four hours, although return times are not guaranteed.
- Bring a lunch or snacks; we'll take a food break at China Beach before we turn around to return to Lands End.
- Weather forecast: It's April in SF, so light mist/rain is possible, but most likely fog and light sun.
- Kids are welcome if they can handle the five miles. If your kid poops out part-way, finding your way back on your own is easy.
- No dogs.
- Donations accepted. I'll pass around my hat at the start of the hike and suggest $2/person.
There's no RSVP limit, but we averaging 15-25 folks. No-shows are penalized, but please remember to change your RSVP if you change your plans.
Meet at Lands End Trailhead at the far (northwest) end of the parking lot at the North side of Point Lobos Ave, just west of 48th St. There is a big parking lot, but if it fills up look across the street just below the main parking lot for overflow.
Those on public transit can take the 38 Geary to "the end of the line" two blocks away. For East Bay folks, the 38 is a relatively quick trip from BART; I think there's also a reasonable CalTrain connection, although I don't know it (http://511.org is great for transit trip planning).
Gather at 10:00 AM. I'll give an introductory talk with a bit of background on the region, if you've heard this before, just make sure you arrive by 10:15. If you get there late and can't find us, my cell number is five one oh, 495-7035 (please post advanced questions by email, not by phone).
Links to previous times we've done this hike:
30 attendees
Mt. Lassen hiking and camping
Location not specified yetJoin us for three days of exploring the geology of Lassen Volcanic National Park. We’ve reserved a group site at Lost Creek Group Campground for June 26–30, which accommodates up to 20 people.
We’ll begin accepting RSVPs in late March or early April, but wanted to share the dates now so you can add them to your calendar.
The trip will include three full days of hiking on June 27–29, with plans for:- A summit hike (about 5 miles with 2,000 feet of elevation gain)
- A hike through the park’s geothermal features
- One additional hike (details to come)
Most hikes will be moderate, though the summit hike is strenuous—it’s a steady climb most of the way up. Participants are welcome to skip any hike they’re not comfortable with, but campsite reservations will be prioritized for those planning to hike on at least two days.
If camping isn’t your preference, there are B&Bs and other lodging options available just outside the park’s north entrance. Those staying off-site are very welcome to join us for the hikes and unwind together around the campfire in the evenings.
We may also add an optional extension to explore Lava Beds National Monument, which would include one half-day and one full day of exploring. If offered, this extension will be listed as a separate trip.
More details about our trips can be found here.
Previous trips to Lassen include:- July 2021 (Mt Lassen & Lava Beds listed separately--this year there was smoke from a bad fire and we ended up not going to Lava Beds)
- August 2013
- July 2011
19 attendees
Past events
243
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