Tips from a local geologist on visiting the Mendocino Coast
Last month, we guided you on a daytrip tour of the Sonoma County coastline, seen through the eyes of a geologist. Now we venture farther north, to the Mendocino County Coast, where the interesting rock formations, unique beaches and natural landmarks continue.
While it sounds odd, to get to the South Coast, you have to drive through the North Coast. That’s because Mendocino County residents refer to the coastal area south of Fort Bragg to Gualala as the South Coast, and the Sonoma County region that runs from Bodega Bay north to the Gualala River is referred to as the North Coast.
Gualala (pronounced “Wah-la-la” by locals, from the original Pomo name) is 6 miles north of The Sea Ranch and just over the Sonoma-Mendocino county line. The unincorporated community offers lodging, camping, groceries, shops and the only bookstore on the coast south of Mendocino (Four-Eyed Frog Books in the Cypress Village shopping center).
The Redwood Coast Land Conservancy, through an unnamed buyer, is purchasing 112 acres just inside the mouth of the Gualala River, at the south entrance to Gualala. The land includes an estuary, wetlands and the site of old timber mills once owned by logging companies. The river is accessible, and there are plans for trails along the river and estuary.
The Gualala River basin covers 300 square miles, from Lake Sonoma to the coast. The San Andreas Fault cuts a nearly straight line down the major north and south forks of the Gualala River, then follows the Garcia River to Point Arena.
Five miles north of Gualala is Anchor Bay (Highway 1 postmile marker 4.6), with a small strip of shops and a couple of restaurants (Mexican and Thai). On the north edge of town is a campground at the cove with a marvelous beach area. Although private, it’s accessible to the public for a small fee.
Just 10 miles north is Hearn Gulch, another acquisition held by the Redwood Land Conservancy. This is a must-see scenic-plus-geologic stop. At the boundary of the yellow sandstone of the Galloway Formation and the black rocks of the Iversen Basalt, you’ll find the only igneous rock you will encounter on the “South Coast.” This consists of a series of thin black pillow basalt rocks with white inclusions of a mineral and vesicles (small cavities) of what were previously gas bubbles. At Schooner Gulch (postmile marker 11.35), a fault ends the basalt layer.
Rock spheres, sinkholes
If you can go when the tide is low, visit Bowling Ball Beach, just north of Galloway Creek, as the truly unique “bowling balls” can only be seen at low tide. These round rock balls are an astonishing 3 to 4 feet in diameter and number about 100. They lie in perfect bowling ball “lanes” and consist of sandstone.
How were they formed? Why are they close to each other and in straight lines? And are they eroding out of the bedrock formation or did they get there in some other way? Some people believe the bowling balls were rolled around by the ocean and left in this particular spot. A true geological puzzle!
A mile north at Pelican Beach is Moat Creek (postmile marker 12.89), with the strangest rocks you will encounter in the area. Here there are faults, anticlines and synclines (folds in stratified rock), a mess to understand geologically. Apparently these are deep-water landslide deposits, probably formed at the edge of the Continental Shelf. A storm or an earthquake caused these unstable sediments to slip off the edge of our continent.
Point Arena is 15 miles north of Gualala and has a city government, unlike the unincorporated communities nearby along the coast. It’s an interesting small town populated by people with diverse interests. The library and theater are owned and maintained by local residents. The theater is one of the few places in California where you could watch the Met Opera via live telecast (pre-COVID-19, of course). These taped events are now offered streaming from their homepage, ArenaTheater.org, and are free.
Set on 23 acres, the Point Arena Lighthouse also is owned by locals, and this year they’re celebrating their 150th anniversary with lots of commemorative merchandise available at the Light Station Store as well as their new outdoor museum. Open from 10 a.m. – 3:30 p.m. daily, admission is $5 per person and children under 12 are free. PointArenaLighthouse.com has more information. The historic lighthouse itself is closed due to COVID-19 restrictions, given its tight interior spaces.
Sinkholes like the one that opened up near the lighthouse in early 2019 are caused by waves working in sea caves which capture the overlying material. Sadly, this erosion just east of the lighthouse will continue.