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Aug 30 2013

Friday Photos: Whidbey Island Erosion

Whidbey Island, Washington is a fantastic place to see glacial deposits while you enjoy some seascapes.

Bluff at Penn Cove, Monroe Landing, on Whidbey Island. The bluff is chock full of glacial deposits. The beach is a delightful jumble of rocks, mud flats, and sand, where you can break up your geological investigations by amusing yourself with little crabs, clams, and if you’re very lucky, a live shrimp.

You can also see excellent evidence of why it’s not a good idea to build on a bluff. We didn’t actually mean to see those. My intrepid companion and I meant to go see a fine example of a clastic dike. I should have remembered lessons learned from Doctor Who: “Turn Left.” If I had, we’d have ended up at Blowers Bluff as intended. But, like Donna, we turned right, and will have to get it right (left?) on a second go.

No matter. It turned out to be a happy little accident. There’s enough in the bluff that is not Blowers Bluff to keep a person interested in both geology and sea critters happy for hours. And it has some textbook examples of erosion.

Root ball in eroding bluff. This tree is going to find itself slip-siding down onto the beach, if it hasn’t already.

These glacial sediments are quite firm, even hard, but they’re more like dried mud than rocks: classic unconsolidated sediments, which haven’t had the opportunity to turn to stone just yet. And between the waves from Puget Sound and the gargantuan amounts of rain we get here in the winter, they have a habit of eroding rapidly.

Erosion. You can see in this photo that parts of the bluff are well on their way to becoming beach, and it looks like there’s some slumping going on to the right. Chunks of the bluff are sloughing off.

This is why Scenic Heights Road is endeavoring to become Scenic Lows Road.

Erosion undermining the road.

There were moments photographing this bluff when I questioned the wisdom of standing beneath it. This closeup of the eroded bit of road should explain why:

Closeup of erosion undermining the road.

The US Geological Survey estimates that 51% of Island County’s shorelines are unstable (pdf). All around Puget Sound, you can see signs of mass wasting. Waves make the bluffs too steep, while soaking rains cause the compacted sediments to lose cohesion, leading to landslides and debris flows. It can get rather exciting round here in the winter.

Before I began my geological adventures, I used to think I’d like a nice house on the seashore, probably perched up high with a view of the ocean. These days, I’m content living inland. Don’t get me wrong: I liked The Little Mermaid, but I’d rather not have “Under the Sea” stuck in my head because that’s where my house landed.

 

References:

Tucker, Dave (2010): “Blowers Bluff, Whidbey Island.” Northwest Geology Field Trips.

Crucher, Suzanne (2008): “Determination of Shoreline Erosion Rates of Double Bluff.” University of Washington Earth & Space Sciences.

Shipman, Hugh (2004): “Coastal Bluffs and Sea Cliffs on Puget Sound, Washington.” U.S. Geological Survey Professional Paper 1693.

 

Previously published at Scientific American/Rosetta Stones.

7 comments

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  1. 1
    StevoR : Free West Papua, free Tibet, let the Chagossians return!

    There’s enough in the bluff that is not Blowers Bluff to keep a person interested in both geology and sea critters happy for hours. And it has some textbook examples of erosion.

    Textbook eh? I’d have said field work examples myself, but, great anyhow. ;-)

  2. 2
    rq

    Well, the textbook had to get its examples from somewhere.

    That road looks awfully sketchy, though… On the plus side, they can save money by slowly building the bridge in under the road, rather than having to start from scratch with all the supports and complicated pouring of concrete after it falls in. Right? ;)
    And here’s a question, if there are so many bluffs eroding above the beach, why is the beach, to all appearances (from the photo, that is), a pebble beach? Or is the beach directly below the bluff a sand beach, and the pebble beach is just there for the scenery, and not below the actual bluffs at all (which I suspect)?

  3. 3
    Gregory in Seattle

    @rq #2 – The fine sediments gets washed away by wind, rain and wave, leaving only the larger stones behind. The Puget Sound is pretty sheltered and doesn’t have the kind of pounding surf that would reduce the rocks to sand. Thus, like most of the coastline in the Sound, a pebble beach.

  4. 4
    Trebuchet

    Very nice! My sister-in-law used to live just about a block off Scenic Heights Road, on Shady Lane. Really! I always liked visiting and taking her kids on a walk to the beach.

    A lot of our bluffs are made of clay, which both retains water and is slippery when wet. Not a good combination for stability. People then come along and install houses with septic systems on them!

  5. 5
    Anne Murphy

    Another great spot to see Whidbey erosion is along West Beach Road. There’s a little pull-out parking lot at the south end of the no-bank waterfront houses (identifiable by the crumbling bulkhead that’s usually covered by grafitti). Park there, then walk south along the base of the bluff for a great look at erosion in action.

  6. 6
    =8)-DX

    a nice house on the seashore, probably perched up high with a view of the ocean.

    Odd that you thought of Little Mermaid, I immediately jumped to: Ponyo on the cliff.. there home is almost idylic, their own generator, water, radio, the perfect view and by the sea..

  7. 7
    George Stelle

    You left out what I find to be the coolest part of those bluffs! http://en.wikipedia.org/wiki/Midden#Shell_middens . There used to be a good sized indigenous settlement right in that area, and as a result there is a large exposed mussel shell midden in the cliff. If I recall correctly it is most prominent right around where the cliff starts.

    Source: the field visible in the first photograph belongs to my parents :).

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