Point Reyes Walkabout

Kehoe Marsh and McClures Beach in Winter

January 2, 2013

This post about McClures Beach is the second-to-last post in Jules Evens’s yearlong quest to hike and write about every trail at Point Reyes National Seashore, which turned 50 years old in 2012.

Note: We just heard from reader Sandy Steinman that McClures trail was close don Dec 29, 2012 due to rock slides. For now, we’ll have to enjoy Jules’s words and photos while awaiting news on the trail’s reopening!


In every outthrust headland, in every curving beach, in every grain of sand there is the story of the earth.   —Rachel Carson

Overcast, rain imminent, late afternoon, minus tide with Terry Nordbye.

These two short trails lead to one of the most dramatic and ecologically interesting stretches of beach on the peninsula—Kehoe Beach and McClures Beach. The walk from the end of one trail to the other along the outer beach is difficult and dangerous unless you time the trek to coincide with an extremely low tide. Three granitic “outthrust headlands” intersect the shoreline, jutting into the tidal reach from the coastal cliffs. This afternoon was a minus 1.5’ tide, so we decided to try to walk from Kehoe to McClures, about 3-miles northward along the shore.

Gulls gather along the beach in Point Reyes
Gulls gather along the beach where the freshwater from Kehoe Marsh flows into the breakers forming a functional, though temporary, estuarine zone.

The geology is well-exposed north of the entrance to the beach, bound on the upland margin by steep cliffs of Laird sandstone (of the Miocene) overlying granitic basement rock (of the Cretaceous). Even without plumbing the depth of their geomorphology, these cliffs lend interesting insight into the tumultuous and mysterious origins of the peninsula—rising-and-falling seas, and uber-tectonic tumult.

Laird sandstone where the Kehoe Beach trail meets the shore dunes.
Laird sandstone where the Kehoe Beach trail meets the shore dunes. Fossilized mollusks and urchins at the base of this tilted rock face indicate its formation in shallow seas during the middle Miocene (about 16 to 11 million years ago). The tall grass like vegetation in the dunes is European Beach Grass (Ammophila arenaria), introduced to California to stabilize dunes. It has accomplished its intended purpose, but unfortunately displaced many native species.
Granitic exposure at Point Reyes
Salinian granitic coastal cliffs just north of the Kehoe Beach trail reveal the bedrock that underlies the entire peninsula, of the Cretaceous period (145-66 milion years ago). This basement formation is overlain by younger sandstone, marine and alluvial deposits of much younger origins (Miocene to lower Pliocene).


The rocky intertidal is all about real estate; “personal space” is sacrificed for a small patch of property, every millimeter matters. The granitic boulders that extend out into the intertidal off Kehoe Beach are covered with dense colonies of intertidal invertebrates. In the high intertidal the California mussel (Mytilus californicus) is the dominant resident, securing a foothold with its ability to attach to the rocky substrate. A glue-like secretion anchors the “beard,” or byssal threads, and allows the mussel to remain in place despite intense wave action. The “mussel-barnacle” zone rarely extend into the lower intertidal, because at lower elevations, ochre sea stars (Pisaster ochraceous) are highly effective predators of both mussels and barnacles.

Black oystercatchers at Point Reyes
The high to middle intertidal is also called the “mussel-barnacle zone,” for obvious reasons. Black Oystercatchers are in their element among the dense beds of bivalves. Contrary to the species’ name, oysters are rarely taken—mussels, limpets and crabs are the main food items. That stout red bill is evolution’s effective chisel, the perfect tool for prying open a mussel shell and severing the adductor muscle.
Gooseneck barnacles and mussels
Goose-necked barnacles (Pollicipes polymerus) are common in the middle intertidal, crowded in closely with California mussels (Mytilus californianus), where they attach to rocks and mussels with their rubbery stalks (peduncles). Barnacles are hermaphrodites, so they always have a date on Saturday night.

Pisaster is not the only predatory invertebrate in the lower intertidal. Anemone’s are common here too, although they are passive (sessile) predators, laying in wait for whatever the tide sweeps into their tentacles. The tentacles are fully extended when submerged, and each contains spring-loaded stinging cells (nematocycts) that paralyze the prey, be it detached mussel, urchin, crab, or small fish. Two species of anemone are most common along these shores—the Giant Green Anemone and the much smaller Aggregating Anemone.

Aggregating anemones
Aggregating anemones (Anthopleura elegantissima) crowd into dense colonies just below mussels-barnacle zone. Relatively small for an anemone (about 1-2 inches across), grains of sand and bits of shell adhere to their bodies providing camouflage. Within its body tissue, this anemone hosts photosynthetic organisms that contribute to the anemone’s nutrition another example of nature’s symbiotic model.
Giant green anemone
Giant green anemone (Anthopleura xanthogrammica) tends to be somewhat solitary, but like the aggregating anemone, this species also harbors photosynthetic symbionts, hence the green color, and becomes decorated with pebbles and shell fragments. The black tar-like material on the rock above is an algae, Ralfsia.

The low tide has exposed the subtidal community, and we search the smaller pools for some of the rare and seldom seen critters that can be found here. Nudibranchs, the inelegantly named “sea slugs,” are the most sought after because of their striking beauty—the butterflies of the invertebrate community. The common ones along our shore have names as exotic as their beauty—Hermissenda, Dialulua, Catalina, Aplysia. Our time is limited and we are exposed to incoming tide, so our search ends unsuccessfully. For an excellent introduction to these mysterious and gorgeous creatures, see California Academy of Sciences’ brief video.

Algal beds
Algal beds. Plants colonize the lower rocks where invertebrates are less dominant. Brown and red algae are represented here. The browns include the long “feather boa” (Egregia) in the center and the single blades at the end of long stems (Laminaria), upper left. The encrusting blackish blobs are “tar-spot” brown algae (Ralfsia). The pinkish tufts are a red alga (Gracilaria).

After crawling through a fissure in the rocks that separates Kehoe from McClures Beach, we find the tide pools and slippery rocks too daunting and too dangerous to continue, so we turn around, retrace our steps back to the car and drive to the McClures Beach trail.

A window in the granitic hogback that separates Kehoe and McClures
A window in the granitic hogback that separates Kehoe and McClures is just large enough for a humanoid to squeeze through. This fissure, well above the high tide line, allows access to the remote stretch of shoreline that connects Kehoe and McClures beaches.

The half-mile trail that descends from the McClures Beach Trailhead passes through an ancient dune system that was deposited by wind within the last two million years. The cliff faces, well exposed where the trail reaches the beach, are beautifully fluted by the persistent forces of wind and rain.

McClures Beach cliffs
The beach at McClures is bound by nearly vertical sandstone cliffs, deposited in the Quaternary, probably “before or during the last ice age.” (Download a USGS doc about that here.)

As I’ve discovered before, one of the pleasures of a desultory walk taken with open eyes and an open mind and heart is to happen upon unexpected or ephemeral beauty in familiar places. Such serendipity is sometimes amplified by its ephemeral nature.

Patterns in the sand
As the uplands judiciously release their moisture following rains, the freshwater seeps beneath the beach, then daylights downslope, creating intricate dendritic patterns in the sand.

At the end of the day, in the fading light, the shoreline and the skyline converge to provide yet another alluring panorama. As we’ve said to each other several times today, how fortunate we are to be in a place of such spectacular radiance.

McClures Beach Sunset
Leaving McClures at sunset, another moment of beauty and peace that the more remote reaches of the peninsula provide.


About the Author

Naturalist and writer Jules Evens has lived near Point Reyes for over 30 years. He is the founder of Avocet Research Associates and the author of The Natural History of the Point Reyes Peninsula and An Introduction to California Birdlife (both UC Press).

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