Sea Stacks

Fifteen to sixteen million years ago, a lava flow from the Blue Mountains of eastern Oregon reached the northwestern coast of Oregon and solidified. Over the ensuing time relentless wave and wind action have caused fractures and erosion to create the giant rocks we see today. They used to be part of the mainland, but have been eroded away. This origin story is easy to understand. Haystack Rock off of Cannon Beach is one such example.

Further south things are more complicated. We will take the formations that are off the coast near Bandon for our example. Some parts of these rocks were formed 201 million years ago and other parts were formed a mere 56 million years ago. And other parts were formed between those times. They are a mix of metamorphic and sedimentary rock. Formed at the bottom of the ocean, lifted above, sunken again, and this may have repeated multiple times. It is part of what is called the Sixes River Terrane. A terrane is a chunk of the earths crust bounded by faults with a distinct structure and history. The Sixes River Terrane used to belong to another tectonic plate, but as it’s plate was subducted by the North American Plate it was scraped off and accreted to our plate. This took place 200 million years ago and the terrane may have originated in California.

However, once these crazy mixed up chunks of crust were in place along the coast, the relentless wind and wave action caused the same kind of erosion as happened further north, creating these giant rocks offshore.

These giant rocks are properly called sea stacks. They may take on fantastical shapes and are often named for what they look like. Face Rock off Bandon is one such sea stack. The Coquille people’s origins story is that it is the face of Princess Ewauna, daughter of Chief Siskiyou, who was lured out to sea and turned to stone.

Happy Trails…

P.S. This blog is going on vacation over the weekend. I will start again on Monday as I head back out to finish the OCT.