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Up The Road: North Coast Tour: Studying Geology “On The Brink”

Bob Wick
US Bureau of Land Management

The Great California Road Trip has rolled west—to explore more of the North Coast, “the brink of the world,” as an ancient Ohlone dancing song has it. Gain new appreciation of our edge of the world, up close and personal, by taking along a nifty state parks geology guide produced with help from the California Geological Survey.

Geological Gems of California State Parks, available online as a free download, includes 50 different geological “notes” that describe and illustrate key geological processes and unique features you’ll see at parks all over the Golden State.

Before we go, a quickie review:

Known for its volcanism and countless earthquakes—an average of 15,000 shakers every year, believe it or not, though most don’t amount to much—California nonetheless perches confidently on the edge of the Pacific Ring of Fire. Native peoples have always explained California’s fiery, earth-shaking temperament in marvelous myths and legends, but there are scientific creation stories too.

According to the theory of plate tectonics, the most widely accepted of these, the earth’s crust is divided into 20 or so major solid rock (or lithospheric) “plates” upon which both land and sea ride, the earth’s crust. The interactions of these plates create all earth movement, from continental drift and landforms to volcanic explosions and earthquakes.

Most of California teeters on the western edge of the vast North American Plate. The adjacent Pacific Plate, which first collided with what is now California about 250 million years ago, grinds slowly but steadily north (to Alaska), along a line more or less defined by the famous San Andreas Fault. Plate movement itself is imperceptible: at the rate things are going, within 10 million years or so Los Angeles will become San Francisco’s next-door neighbor.

Credit Bob Wick / US Bureau of Land Management
US Bureau of Land Management
The rugged, rocky North Coast has its peaceful  moments.

But the steady friction and tension create sudden events too—such as the instant, jolting slippage responsible for the massive 1906 San Francisco earthquake and fire as well as the city’s more recent shake-up in 1989.

After reminding us that California’s unique landscape, the interplay of landforms, habitats, and climate, is the result of geology, Geo Gems “land ’splains” the Coast Ranges. The largely soft underlying sedimentary rock—sediments once accumulated on the ocean floor, then uplifted—mixed with other rocks through tectonic collisions to create the Franciscan Complex “mélange,” or mixture.

The tortured result of further tectonic collisions, compression, and erosion over the eons—notably twisted hard-rock cliffs and characteristic offshore sea stacks—is what you’ll see all along the coast, including Del Norte Coast Redwoods State Park near Crescent City.

But there are surprises, too, especially from lands associated with the Mendocino Triple Junction earthquake faults. Such as polished jade pebbles in Humboldt Redwoods’ South Fork of the Eel River, and rare, ephemeral pink and purple sand beaches composed of garnet sand—but here today, gone tomorrow—along the southern part of California’s “Lost Coast,” Sinkyone Wilderness State Park. More on all that next time.

Up the Road Encourages Responsible, Safe Travel

Here are previous Up the Road episodes that explore why we should travel, how to do it responsibly, and how to travel responsibly now, in the shadow of COVID-19. Not everyone should be traveling now, of course. But everyone who does travel needs to do so responsibly, to prevent viral spread. Take a listen:

Photo Credit #1

Photo Credit #2

Kim Weir, a former NSPR news reporter, is editor and founder of Up the Road, a nonprofit public-interest journalism project dedicated to sustaining the Northern California story. She is also an active member of the Society of American Travel Writers. North State Public Radio’s Up the Road program is jointly produced by Up the Road.
Matt Fidler is a producer and sound designer with over 15 years’ experience producing nationally distributed public radio programs. He has worked for shows such as Freakonomics Radio, Selected Shorts, Studio 360, The New Yorker Radio Hour and The Takeaway. In 2017, Matt launched the language podcast Very Bad Words, hitting the #28 spot in the iTunes podcast charts.