A Quick Trip to the Ocean Shore

For a few days near the end of 2017, Cheryl and I went with two friends to Iron Springs Resort, on the Pacific Coast of Washington, between the (not) world famous towns of Moclips and Copalis Beach. We love the ocean, the beach, the sound and swash of surf, the flooding and ebbing tides, the flocks of sandpipers, the coastal forests and marshes, the estuaries where rivers interchange with ocean, the bald eagles, the great blue herons, the sand dollars, the seafood. The escape from crowds and major retail centers. And I got some bits of geology along the way.

Iron Springs Resort, at the mouth of Boone Creek. We stayed in the cabin to the left of the highest cabin, with views through picture windows across the creek and beach to the ocean, and each evening a fire we built burning in the fireplace. Underlying the cabins are layers of sediment that form low bluffs along this part of the coast. How did those layers of sediment form? How old are they?

The reddish color in the layers of sediment that form the bluffs along the beaches near Iron Springs comes from oxidation of iron in the minerals that form some of the sediment grains. Because a lot of the sediment grains are eroded pieces of Crescent Formation basalt, which has a lot of iron in it, the bluff is rather rusty. It may be that the red color of the local cliffs is how Iron Springs got its name, but see this history of Iron Springs Resort for other possible sources of the name.

These layers of sand and silt are depicted on the geologic map (see below) as Qoa, outwash from the Quaternary epoch (between 2.6 million and 11.7 thousand years ago) shed by alpine glaciers that grew large on the nearby flank of the Olympic Mountains and extended down toward the coast in the larger river valleys. They are older than the most recent glaciation, the "Wisconsin" age glaciation that ended between 12,000 and 20,000 years ago. (How do we know these rusty layers of stream-laid sediment are older than Wisconsin? Because in other places nearby, they can be seen underneath the younger, less coherent, less rusty Wisconsin-age glacial outwash sediments.)

A scallop-shaped concavity in the bluff is where a recent landslide occurred. The debris it left on the bottom of the cliff forms a mound temporarily stabilized by vegetation adapted to the ephemeral habitat. As you walk along the beach, you can see one scallop-shaped landslide site after another, each fronted by a vegetated mound at the base of the cliff/back of the beach.

The coastal forests feel familiar to me. I grew up on Puget Sound and frequently visited the northern Olympic Peninsula coast where my grandpa Roy and grandma Gretchen had a cabin on a bluff overlooking Dungeness Spit and the Strait of Juan de Fuca.

Inland from the resort is a small network of trails through the coastal forest. Based on the big old sawn stumps, and the not-so-big, more-recently-sawn stumps, this patch of forest has been logged at least twice, and is still thinned and trimmed on a selective basis.

Despite being logged more than once, the Iron Springs woods have some pretty big trees, some new trees growing out of dead-tree nurse logs, and enough mosses, lichens, and ferns to make me feel at home.

This is Boone Creek from the side of Highway 109, looking at part of Iron Springs Resort. The rip-rap boulders brought in to stabilize the shoulder of the road above the culvert consist of basalt.

Here is a basalt pillow with flow lines across its surface, formed when the lava was still oozing and enlarging the pillow as it erupted on the floor of the ocean and the rind was cooling and solidifying. Presumably these basalt pillows and chunks of volcanic breccia from spalled and broken pillows are from a nearby quarry, and are part of the Crescent Formation, Eocene-age (about 50 million years old) oceanic crust that was accreted to the edge of North America as a result of the Juan de Fuca Plate subducting beneath the leading edge of our continent, which it continues to do today, occasionally accumulating enough pent-up tectonic strain to generate huge earthquakes that spawn giant wave surges - tsunami- that inundate low-lying part of the coast. If we had felt an earthquake while at beach level, we would have headed immediately for higher up, out of reach of tsunami.

The tracks on the beach may have been left by snails (that's what Ken, the paleontologist of the group, the one with the most knowledge of biology, suggested). The shell is that of a razor clam. People come from miles around to dig the meaty, tasty razor clams, which burrow quickly through the fine sand with their narrow, sharp-edged shells, making it a challenge to dig them up faster than they can burrow on down beyond your reach. It was not razor clam season or we would have seen a lot more people, and cars, on the beach at low tide. (Motorized vehicles are allowed on some stretches of beach in this part of the Washington state coast.)

The beach sediment is mostly a mixture of fine sand, silt, and, in some places, clay. Not a rocky or shingly beach. Out near the surf, I could find no stones large enough to throw. The lack of coarse-grained sediment on the beach is due to the fact that hardly any solid bedrock, such as Crescent Formation basalt, is exposed along the shore. Instead, the bedrock is mantled by and hidden beneath glacial drift sediments, alluvial sediment spread by rivers entering the ocean via estuaries, and alluvial sediments spread by small streams that fan out across the beach on their way into the surf. It is from these young, fine-grained sediment sources that the littoral sediments (beach sediments) are derived.

Our twice-a-day beach walks took us along short little bits of the Pacific Ocean's edge edge. Though the Pacific spans about 1/3 of the Earth, it is a shrinking descendant its predecessor, the Panthalassa Ocean, which once straddled 2/3 of the world. That was 250 million years ago, before Pangea broke up. As the continents rifted apart and began steadily drifting away from each other, new subduction zones formed in front of them, swallowing the Panthalassa Ocean floor beneath the advancing plates, shrinking its basin. This process continues happening today around the ocean, from Tierra del Fuego to the Aleutian Islands, the Kamchatka Peninsula of Russia to New Zealand - and of course, here along the Pacific Northwest coast. 

The ocean may look peaceful (hence the name) and the sound of the surf may sound soothing (if you're not in it), but we get lulled by these quieter intervals of more gradual geologic processes that occur between catastrophes. The geology around the edge of the Pacific Ocean is wracked and upheaved by volcanic eruptions and huge earthquakes. 

People who experienced the eruption of Mount Saint Helens on May 18, 1980, know this. People who experienced the Good Friday earthquake in Alaska on March 27, 1964, know this. But still, it is pleasant to enjoy the quiet times between.

A great blue heron in the estuary of the Copalis River. Where the river leaves the inland coastal zone and enters the littoral (i.e. active beach) zone, where the beach is actually a current of sand and other sediment being moved by waves, tides, and currents, the river turns sharply north (see the map below). So do other rivers entering the ocean along this stretch of coastline. This illustrates that the littoral drift (the direction the waves and storms are moving the beach sediments) is to the north. Sand dumped to the shore zone by the Copalis River has been picked up and re-deposited by the wind into a dune field.

Our last walk was in Griffiths-Priday State Park at Copalis Beach. The trail follows alongside the Copalis River estuary to where the river crosses the beach and joins the ocean.

After we got home at the end of the week, Cheryl pointed out that the calendar on the wall, from the Washington Native Plant Society, had a relevant image for December.

Picture of the image above the month of December, 2017, in our Washington Native Plant Society calendar. The caption speaks for itself.

Detail from the "Geologic Map of Southwest Washington" by Timothy Walsh and others, 1987, Washington State Department of Natural Resources. Boone Creek is the next stream entering the ocean north of the Copalis River, at the unlabeled site of Iron Springs. "Qoa," pre-Wisconsin Quaternary alpine glacial outwash (from one or more glaciers that came partway down to the coast in river valleys from the Olympic Mountains), forms the reddish-colored layers of sand and silt that underlie the cabins and form the scenic bluffs at Iron Springs Resort. "Ev_c?" is Eocene-age basalt or broken basalt formation, either the Crescent Formation, or broken up in a subduction zone mélange derived from the Crescent Formation. The offshore rock labeled "Ev_c?" is called Copalis Rock.

Meera, Ken, and Cheryl on the beach between Iron Springs and the Copalis River, with Copalis Rock in the background. Copalis Rock is made of basalt of the Eocene-age (50 or so million years old) Crescent Formation. Sticking up from the right-hand end of Copalis Rock, above and to the left of Ken's head, is a bald eagle, which Ken, with his eagle eyes, spotted from a long ways away.