Northern Tier 2010

July 2, 2010

Fog, as Far as the Eye Can See

Filed under: Geology, Pre-Tour Vacation — Henry Scott @ 8:00 pm


We’re staying at the Log Cabin Resort on Crescent Lake in Olympic National Park (ONP) for three days, and tonight will be the second. It is particularly interesting for me to be here because just the week before last I lectured about the geology of this park, yet I hadn’t seen it first hand. Briefly, ONP is an excellent example of an actively forming (and simultaneously eroding) accretionary wedge: a rugged landscape formed from material scraped off of the seafloor as the Pacific Ocean’s Juan de Fuca plate subducts beneath North America — this has been going on for tens of millions of years!

Accordingly, the rocks one sees in ONP are from the seafloor, such as sandstones, shales and basalts. Basalt is a volcanic rock, and much of the basalt in ONP shows telltale signs that it erupted under water: as the molten rock poured from fissures at the bottom of the ocean, it was quickly cooled by the water, and as it solidified it impeded the flow of more lava in the same spot. Each new pulse of lava was stopped in its tracks and frozen in time as a rigid blob. Some think the rigid blobs look like pillows, despite have no comfort qualities, and they are usually referred to as “pillow” basalts for this reason. I’m pointing to an individual pillow in the picture above, but entire hillsides are formed from them. We took this particular shot along the Hurricane Ridge Road.


The sandstones and shales are often found as alternating layers in outcrops, and form as submarine landslides move accumulating sediment from shallow waters nearshore down steep slopes to deeper waters. These flows are referred to as a turbidity currents. Notably, the relatively coarse sand-sized grains settle out first, and the finer grains that eventually make shale take much longer to settle. Each new flow produces this progression, and the resulting layered rocks are called turbidites. The image at left shows a not just a turbidite, but one that has been tilted up at an angle and faulted a bit — not surprising given that these rocks were scraped off of the seafloor.

We also saw lots of wildflowers, and some deer and marmots during a hike we took up the Hurricane Hill Trail. Unfortunately, it was too foggy to see any good vistas, but it was very cool to feel like we were walking into a cloud. And we were!

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3 Comments »

  1. Henry, this is awesome. Glad you had a great start. Your route looks like you are going into Canada(just barely crossing the border). No french on this side of Canada. I am going to show this to my Earth and Atmopsheric Science students the geology is great!! Hope you have great weather espcially in the mountains. Take more pics of flowers if you get a chance…deer looks the same as the ones that run into our car.

    Comment by Barb and Ed — July 3, 2010 @ 9:24 pm

  2. Glad to hear you’re well and that the trip has been hassle-free so far. As I told you when we returned from Zion/Bryce Canyon/Grand Canyon, your geology knowledge is enviable. Cheers to Jennifer! Take care, my friend,

    Comment by Bruce — July 3, 2010 @ 11:22 pm

  3. love the info. im taking a summer geology class and your pics and info were a great help. I’m passing it onto my instructor.

    Comment by just a human — June 30, 2012 @ 3:48 pm


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