Yesterday I hiked the 1 ½ mile San Andreas Earthquake Trail in the Los Trancos Open Space Preserve. To reach the Preserve from Highway 280, you must drive 7 miles up a long and winding road, a drive of about 30 minutes. The Preserve is located on Montebello Ridge 2,000 feet above Palo Alto in the Santa Cruz Mountains.
At the summit, I enjoy the expansive view from Black Mountain, to Stevens Creek Canyon (the San Andreas Fault) to Loma Prieta Peak (3790 ft.). The Crystal Springs Reservoir is faintly visible in the East. Nearby a sign points to the beginning of the trail, and warns of mountain lions and other hazards.
The trail is marked with numbered posts, each one corresponding to a description in the accompanying brochure. The first post is just a short distance past the parking lot. I stand in a clearing marked by jumbled rocks and boulders. My brochure explains these rocks originated 2 million years ago near the Loma Prieta peak, on the North American Plate. Water has carried them over the San Andreas Fault to the Pacific Plate, and tectonic plate movement has carried them northward. Now they are 23 miles away from their origin.
A depression in the land identifies a sag pond, a place where the earth has stretched. Eventually landslides and erosion will fill in the pond and blend it into the landscape. For now, this “sag” in the earth denotes a relatively recent earthquake (1906).
The path descends into a wood of bay laurel, fir, and oaks. An abundance of willows implies fresh water. The brochure explains that spring water occurs along faults. Why? Because fine clay soil in a fault impedes the natural flow of the water and the water bubbles to the surface.
Poison oak flourishes in an area once subject to a landslide.
These unusual shaped tree trunks tell an interesting story. They are shaped like a bent elbow, growing parallel to the ground and then vertically. An earthquake threw them to the ground without severing their root systems. A branch resumed growing towards the light, resulting in the unusual shape.
The white topped posts signify a minor fault break.
Hikers have been enjoying this trail since 1977.