Rocks are earth’s history books and I love learning what they reveal. I started studying geology in college while exploring my interest in environmental science. Ultimately, I decided that being a geologist was for me! Studying earthquakes, volcanoes and fossils helped me understand more about how the earth works. I deepened my awareness of how the earth changes with time and how its processes unfold. This knowledge is invaluable for planning environmental restoration — which ultimately led me to POST!
The beauty and biodiversity of the Bay Area is unparalleled — from our state flower, the poppy, to our state bird, the quail. Though our state rock is lesser known, it is every bit as iconic. Allow me to introduce you to serpentine. Smooth, slippery and shiny, its mottled surface features shades of green, blue, black and cream. As it breaks down, it eventually forms serpentine soil — home to abundant and rare wildflowers (click here for tips on where to see these bloom)!
As POST’s resident geologist, seeing serpentine fascinates me. Its very presence at the earth’s surface is testament to the dynamic geologic history of our region. It hails from the earth’s mantle; that is, from hundreds of miles below the earth’s surface. It rose to the surface along faults when the ancient Farallon tectonic plate was shoved under the North American plate over a hundred million years ago.
Over time, our compelling state rock breaks down into a special soil. While it only makes up 1% of California’s land overall, it is more common here in the Santa Clara Valley. Reportedly, the single largest untouched stretch of it exists in Coyote Valley, just east of Highway 101. Unsurprisingly, this rare serpentine soil is home to several native plants, many of which are rare themselves or are endangered. Because the serpentine habitat is not abundant to begin with, it is especially at risk of loss due to ongoing human development.
It’s pretty remarkable (and inspiring!) how some native plants have managed to thrive in serpentine soil with its famously harsh nutrient composition. It is low in nutrients like calcium and high in magnesium and heavy metals. For many plants, the environment is toxic. Over millions of years, several native species have proven their resilience by adapting to serpentine soil. As such, these habitats offer a much-needed refuge. In other habitats’ more nutrient-rich soils, the same native plants might find themselves out-competed by other native or various invasive species.
Serpentine soils are home to many endemic species. These species live in particular local habitats that are not found in many places. A pair of local wildflowers — dwarf plantain and purple owl’s clover — grow in serpentine soil areas. These are the primary food sources for the threatened bay checkerspot caterpillar. A rare variant of the Edith’s checkerspot butterfly is another case. They lay their eggs exclusively on plants living on serpentine soils.
This is an example of why the Bay Area is a biodiversity hotspot. You can find a variety of ecosystems in our region because of the geologic history and diversity of rock types at the surface! Geology is at the heart of why this area is so biodiverse. Isn’t that so cool?!
For the flora enthusiasts among us, serpentine areas are ideal for viewing indigenous plants, trees and flowers. During wildflower season, you can see this soil (and the array of beautiful blossoms it nurtures) up close! Here are some of the unique blooms you’ll find at this time of year, and where you can find them.
What You’ll See: Look for serpentine sunflowers, shooting stars, and California buttercups
Preserve information: Click here
What You’ll See: Look for golden yarrow, clay mariposa lily, orange bush monkeyflower
Preserve information: Click here
Here are a few guidelines while viewing wildflowers:
Peninsula Open Space Trust (POST) protects open space on the Peninsula and in the South Bay for the benefit of all. Since its founding in 1977, POST has been responsible for saving more than 87,000 acres as permanently protected land in San Mateo, Santa Clara and Santa Cruz counties. Learn more