Juan de Fuca Plate

A couple of weeks before Christmas, Peggy and I made a trip over to Cape Arago on the Oregon Coast. The waves featured in my January 7^th post were from this trip as is today’s post on Sunset Bay State Park, which is located at the beginning of the Cape just outside of Coos Bay.

The tourist and real estate industries of the Oregon Coast prefer to ignore the next BIG one, or put it off to sometime in the distant future. The folks involved in predicting earthquakes have a different perspective. The sheer number of tsunami evacuation route signs along the Oregon coast speak to their concerns. The Cascadia Subduction Zone is real. A massive 9-point something or other earthquake known as a mega–thrust is in our future. They happen every 300 to 600 years. The last one was in 1700. The oceanic Juan de Fuca plate is diving under the North American continental plate and it will not be denied. It’s stuck right now. Small earthquakes near the surface are creating pressure on the trapped area, however. When it gives, all hell will break loose.

I, for one, pay careful attention to the evacuation routes whenever Peggy and I visit the coast. If the earth shakes, we will be out of there! So what if we leave our welcome mat behind.

Sunset Bay State Park is a geological wonderland when it comes to featuring various aspects of what can happen when a massive earthquake strikes. The most fascinating to me are the stumps of ancient trees. Twelve hundred years ago, a forest stood above the ocean where Sunset Bay now stands. An earthquake caused a subsidence in the land, drowning the forest. At low tides, the remains can still be seen.

I was fascinated by the different shapes of trunks left by the ancient trees.

This ancient tree stump at Sunset Bay State Park bears a strong resemblance to a man doing jumping jacks.

This tree has roots on roots. A genealogist would be impressed.

Incoming tide surrounded the tree trunk and reflected the fluffy clouds in the sky.

Peggy stands in front the ancient tree trunks to provide perspective. Her Covid-19 mask serves as a scarf.

Faults, fractures in the earth’s surface along which the blocks of crust move relative to one another can be seen among the tilted and layered rocks of the Bay at low tide. The rocks, BTW, also provide an excellent area for tide pools that feature sea life loved by kids and adults alike.

Low tide at Sunset Bay. You can see a number of tide pools to explore, but it also shows a clear fault running from left to right. A second fault can be seen behind it. The crust between the faults moves when earthquakes strike.

We spent a few minutes peering into tide pools.

We were impressed by the sea anemone. The slit is the anemone’s mouth, and, for convenience, its anus as well. The tentacles contain stingers filled with a toxin for stunning dinner, which is then transported to its mouth.

For fun, I rendered the anemone in black and white.

While the bay represents an earthquake caused subsidence, the Whiskey Run terrace surrounding the Bay represents uplifts and folding also created by tectonic activity related to the Cascadia Subduction Zone. The wave-caused erosion taking place in Sunset Bay operated on the terrace when it was at sea level. It’s estimated that the land rises approximately three feet every thousand years.

The terrace above Sunset Bay was once at sea level. Like the Bay, waves created the flatness of the terrace.

A close up of the Whiskey Run terrace. The sedimentary layers have been tilted down to the right by tectonic forces and then eroded away by wave action. A layer of dirt/rock has since been laid down on top, providing soil for the forest.

And finally, I would like to feature a strange, non-tectonic feature of Sunset Bay: concretions. Peggy and I first came across these round, rock-like structures on the southern coast of the South Island of New Zealand. They are created when groundwater triggers extra amounts of ‘cement’ around irregularities in the rock such as shells, creating a round structure that continues to grow as more cement is added. The hardness of the covering makes it harder to erode than the surrounding rock.

And these are concretions apparently marching out to sea. Why, I haven’t a clue.

I’ll conclude with a few other photos from Sunset Bay that I found interesting.

Peggy walking through the tunnel that connected our campground to the bay.

And finally, I’ll wrap up this post on Sunset Bay with more waves.

NEW BLOG SCHEDULE: I’ve been working on revising the book on my Liberia Peace Corps experience— adding a few chapters on my experience working for the Peace Corps after I was a Volunteer and updating the chapters I wrote about modern Liberia. Several of you have read the book and a few of you may have even been around when I first blogged it several years ago. Anyway, I am going to reblog it again, adding it to my schedule. On Mondays I will continue to blog my book, It’s 4 AM and a Bear is Standing on top of Me. On Wednesdays, I will blog The Bush Devil Ate Sam. On Fridays, I will continue my travel blog.

Blog a Book Monday: Will you believe I actually have a good day on the Sierra Trek?

Blog a Book Wednesday: Introduction to the Bush Devil Ate Sam

Travel Blog Friday: I return to my Backroad series following Highway 191 through Navajo country in Utah and ending up in Arizona’s Lyman State Park.