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The Daily Bucket is a regular feature of the Backyard Science group.  It is a place to note of any observations you have made of the world around you.  Rain, sun, wind...insects, birds, flowers...meteorites, rocks...seasonal changes...all are worthy additions to the bucket.  Please let us know what is going on around you in a comment.  Include, as close as is comfortable for you, where you are located. Each note is a record that we can refer to in the future as we try to understand the patterns that are quietly unwinding around us.
Olympic National Park
Washington coast
December 2013

(All photos by me. In to enlarge)

Emerging onto Third Beach for a day hike a couple of weeks ago, the shore felt very peaceful, more so than usual in fact, with that sunny sky and no breath of wind. This kind of weather is HIGHLY UNUSUAL out here in December, where 12 feet of rain drench this side of the Olympic Mountains between October and March. WARNING!! If you take a journey to see the sights along this wilderness coastline, be sure to bring raingear, boots and possibly an umbrella. Seriously!

We encountered a bemused Douglas Squirrel soaking up the sun at the driftwood logjam over the creek. Climbing over the driftwood, we head off down the beach, which at mid-tide level has a wide expanse of sand.

landslide 3

landslide 2

Halfway down the beach there's a landslide, with rocks and dirt and plants tumbled across the sand. If the tide was higher, it would block passage further, unless a hiker crawls through or scrambles over. The tide is ebbing, so we can relax, knowing the beach will be wider when we come back.

landslide 4

beachhike below...

Looking at it close-up I could tell this just happened, sometime in the last few days. Would have been exciting to see the cascade, but not from below!

A big Sitka Spruce tree extends farthest out, after being ripped out and rolled on its way down. The remaining branches snapped on landing. An uprooted Red Alder rests on the Spruce and the fresh boulders which have cracked and broken on descent.

landslide 5

landslide 6

This is the Alder, with loose branches of Spruce.

landslide 7

The top of the Spruce trunk impaled the beach, and a few high tides have just started washing sand over the ends of some branches. Looking up the other way we can see bark scraped off, and quite a few woodpecker holes.

landslide 10

landslide 11

Another reason to think this slide is recent is the muddy water seeping out. Runoff water is generally transparent, like this little creek right next to the slide, draining through "clean" sand and gravel.

landslide 8

landslide 23

Besides rocks and broken vegetation, the debris is a mix of multi-colored sediments. There's gray subsoil, a brown layer and a bright yellow layer on top. These are sediments laid down by the series of glaciers advancing and retreating as well as the intervening ice-free times during the Ice Ages. I've read that the yellow layer is "aeolian" or wind-blown. The rusty red patch is a well-rotted tree.

landslide 9

landslide 12

These wide sandy beaches we love to walk only exist because the bedrock there is a weakly compacted "melange" of rocks pushed up by tectonic forces, like a fruit cocktail. The whole Olympic peninsula is composed of rocks from various places out in the Pacific that were packed onto North America by an incoming tectonic plate. Some are harder than others. Where rock is easily eroded, we get indented beaches; the headlands are harder rock eroding more slowly, and protrude into the sea. Washington state DNR has a good field guide with another section here, describing the geology of the area in more detail.

Walking down to the end of the beach we can see the transition. In fact the headland is impassable, so hikers have to go up and over. The circular sign in black and red marks the overland trail. Beyond it is steep bedrock. This is as far as we hike today.

See the waterfall? That's what's known as a "hanging valley": the ocean is eroding the headland faster than the creek is eroding it down. These are the two main forces working on this coastline, to wear away the rock: the ocean, and water running off the land. Both bedrock and loose boulders are thrashed by relentless surf.

landslide 14

landslide 16

landslide 17

landslide 18

Looking back at the headland, we can compare the two kinds the rock here, the steeply vertical headland on the right and the slanted, weaker rock on the left. A less recent landslide is evident there, bare of vegetation. The seastacks on the far right are even harder, more resistant rock. They are what's left of an earlier headland.

landslide 15

Coming up to the landslide on our way back, it's clear how much of the beach it has covered (to get a sense of the scale of this mass of material, check out the scale figure standing in front of it - that's me). It will take some time for a series of high tides and storm surges to wash all this debris away. Boulders and dead trees will remain, and this spot will look like the rest of the beach.

landslide 20

Landslides occur in some places along the beach more than others. The little creek we passed is a clue. It had rained heavily the week before, saturating the hillside, loosening the soil and rocks. Tree roots infiltrate extensively for anchorage, but when the ground becomes soupy, the whole mass slides down. This tree is just hanging on.

landslide 21

There's a circular trail marker where we take the 1.5 mile trail back to the car. The trail goes up fairly steeply here, but this is the easiest route up. Looking below, we can see the creek that has eroded a valley into the hillside, carrying trees down to the beach, forming much of the logjam there. Very likely there have been landslides here too. Young trees fill the valley. These big old trees are safe, for now.

landslide 24

landslide 25

landslide 27

Episode 3 of What I Did on My Holiday Break ;-)


Now I want to hear what's going on in your part of the country. Still in the grip of winter, or are you seeing signs of spring? Please tell us what nature is showing you.

And -

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Originally posted to Backyard Science on Fri Jan 17, 2014 at 06:30 AM PST.

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