Olympic Peninsula

Located just west of Seattle across the Puget Sound, the Olympic Peninsula is a mystical and wondrous locality ripe with deep temperate rainforests, rugged coastline, glaciated mountains, and several other interesting landscapes. A large swath of the area is protected as Olympic National Park, and the possibilities of exploration on “The Peninsula” are endless.

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Geologically speaking, the Olympic Peninsula and mountains are quite interesting, typifying a geologic structure common in subduction zones known as an “accretionary wedge” or “accretionary prism”. As the Juan De Fuca Plate subducts under North America, vast amounts of oceanic sediment accumulated and lithified on the ocean floor get dragged onto the continent, as all of the rock mass lying on the oceanic plate can not slide into the asthenosphere like the plate itself does. Quite literally, the floor is being dragged under these oceanic sediments, and they pile up onto the continental plate. That is an accretionary wedge (or prism), and that is exactly how the Olympic Mountains were built and how they continue to be uplifted today. As these oceanic sediments accumulate on the margin of the continental plate, they become highly folded and faulted, as the subduction of the Juan De Fuca Plate quite literally deforms and distorts the western margin of North America. The majority of the rocks composing the Olympic Peninsula and mountains are oceanic sediments 18-57 million years in age. On the north and east sides of the peninsula, a basalt unit known as the “Siletzia Terrane” outcrops, remnants of a large offshore igneous province, comparable to modern-day Iceland that was sutured onto the western margin of North America. The Siletzia Terrane outcrops on the majority of the Pacific Northwest Coast, from California to Vancouver Island, but it is notably absent in the core of the Olympics. This is because the growth of the Olympic Mountains deformed Siletzia in the area, pushing it north and east as oceanic sediments from the subduction zone accumulated and uplifted during the last 50 million years.

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Today, the Olympic Peninsula and coastline is the closest location to the plate boundary of the Cascadia Subduction Zone in Washington, and as such, is at the greatest risk for a cataclysmic earthquake. In 1700, the Cascadia Subduction Zone ruptured, generating a massive Mw 8.7-9.2 earthquake, instantly sinking the coastline, and generating a deadly 100' high tsunami that barreled towards the coast, as well as across the Pacific to Japan. Another megathrust earthquake here is imminent, and you can read all about it here.

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The Olympic Peninsula is unique in a myriad of ways, perhaps most notably due to the existence of temperate rainforests on the peninsula, including the Hoh and Quinault Rainforests, located on the western side of the Olympic Mountains. Average precipitation in this ecosystem is 12 feet per year, making it the wettest ecosystem in the contiguous United States (Wai’ale’ale on the island of Kauai in Hawaii is wetter). Sitka Spruces, Western Hemlocks, Western Red Cedars, and Coastal Douglas Firs dominate and grow to absolutely immense sizes in the rainforests. Near the Queets River, a particular Sitka Spruce specimen is 244’9” tall and has a diameter of 14’5”. The Olympic Mountains reach a height of 7,965’ at Mount Olympus, their summits glaciated. As such, subalpine ecosystems abound in the upper reaches of the range, complete with Subalpine Fir, Whitebark Pine, and a treasure trove of wildflower species. The leeward side of the Olympics, towards the Puget Sound, is notably drier, receiving only 17” of precipitation per year, though it is still forested. Black Bears, Roosevelt Elk, Mule Deer, Olympic Marmots, Mountain Lions, Bald Eagles, Ospreys, and Raccoons abound in Olympic’s forests. On the coast, Harbor Seals, Sea Lions, Sea Otters, Sea Gulls, and a litany of fish, crustacean, and mollusk species dominate. An interesting factoid pertaining to salmon is that the Elwha River used to be dammed up, but the dam was demolished and the riparian area was restored in 2011 so that salmon could return to the river.

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The Olympic Peninsula has several beautiful spots to explore, from mountain to sea and everything in between. A drive up to Hurricane Ridge is a must, and offers the visitor splendid alpine views of the entire range. Several alpine hikes, such as that to Seven Lakes Basin, also offer stunning views of the range. The Hoh and Quinault Rainforests are must visits as well, as exploring those unique ecosystems is a grand experience. Sol Duc Hot Springs is a wonderful place to soak, relax, and unwind. Lake Crescent is stunningly beautiful and is an amazing place to paddleboard, canoe, or even go for a dip on a hot day. Moving towards the coast, hikes out to Shi Shi Beach, La Push, Kalaloch, and Cape Alava are amazing opportunities to explore the coast and see some beautiful sea stacks and marine wildlife, though timing your visit based on the tides is strongly recommended. Going out to Cape Flattery is interesting, as it is the westernmost point in the contiguous United States. In terms of cultural experiences, the Makah Museum in Neah Bay is a wonderful place to learn about the Native Americans that originally inhabited the Olympic Peninsula, and if you’re into the Twilight books and movies, visiting the town of Forks (where the fictional stories take place) is an interesting tourist trap. All in all, the Olympic Peninsula is a very interesting place in terms of geology, ecology, and culture, and it is well worth a visit.