[gb]

The trail for two to three hundred yards is bisected by a fresh fault - possibly from this summer. It is not a landslide slip because there is a broad bench below and the fault appears to be one of several movements that have happened in this same location over the years. This is about 1-1/4 to 1-1/2 miles west of Bogachiel Peak. The trail in fact appears to have been built directly on an older rendition of this fault and it is now split widthwise by from 2 to about 10' over a distance of 2-300 yards. The trail in this area was built on top of a sharp-crested buckle. There are several transverse faults of up to 10-15' wide and the trail in this area is now a scramble between and over large angular blocks that don't appear that stable - like unstable talus. The fault is pretty much filled with these angular blocks. Several earlier faulting episodes in this area have left parallel cross-slope ridges and troughs that are from a couple of feet to 10 feet or so in height/depth. The fault at one point longitudinally tore apart tree roots. This is the first time I've ever seen something like this, though I know of the large old fault on Kindy Ridge.

[altasnob]

Interesting. The entire coast of Washington reaching into Mt Olympus is listed as the most seismically unstable area of the state, along with Seattle and central Puget Sound. More seismically unstable than the Cascades. The area you describe is right on the boundary of the most seismically unstable area. https://www.dnr.wa.gov/programs-and-services/geology/geologic-hazards/earthquakes-and-faults

[benneke]

I haven't been there this year but that fault section has been there at least since 2018, I'd be interested to hear if it has changed since then

[zimmertr]

Anyone have any photos? I am so darn interested in seeing this I might have to go myself!

[altersego]

I hiked it in August 2017 and remember thinking "why is the trail all effed up here?"

[meck]

I've been around the loop several times over the last few years. I always assumed it was just a massive landslide getting ready to release (as I recall most everything to the west and below has already slid away, looks like a large dirt slope). I'd hate to be there when it goes.

[coldrain108]

I was just up there in July. We had a specific bench shaped rock that we used as a break time rest spot. It was gone. There is a really impressive crack splitting some solid rock. Boulders on end. From a distant vantage point you can see that the entire area is "sliding" into the Bogie river valley.

You can see the side hill trail at the upper right hand side just after the first rock slide. When I first did that route in 1990 the trail didn't go out to the edge like that, it went down into the "vale" and back up to the Lunch Lake drop in. I did this loop as my honeymoon in '90 and I've been back many time since then. Crazy when recognized landmarks disappear. No more "Tea Rock"!

[gb]

[Brushbuffalo]

[Slugman]

I’ve been there twice but each time dropped down to Lunch lake, and so missed that section.

[coldrain108]

[Slugman]

Whoops, last time I was there was 8 years ago.

[Brushbuffalo]

Quoting from "Geology of Olympic National Park" by Rowland Tabor ( p. 103): "At the head of the Bogachiel River, the Bogachiel Peak Trail detours around a peculiar depression filled with a jumble of sandstone blocks. Gravity produced this ridgetop depression by pulling the steeply dipping beds of sandstone away from the Bogachiel Peak ridge and down into the cirque below. It is likely this sort of ridge failure, quite common throughout the Olympics, came shortly after alpine glaciers melted away, removing their support from the oversteepened valley walls." I reported on similar features on another High Divide and ( less prominently) on Anderson Mountain in Whatcom County. There is a photo and drawing ( fig. 83 in this book) that matches the one submitted by coldrain108 in this thread. The prominent gray slope of boulders below and to the left of the higher depression is shown, and as several posters have commented, periodic movement is ongoing. Earth is always changing on different space and time scales... sometimes slowly, sometimes catastrophically, at still other times at rates that tumble boulders about and produce surface scarps that develop in hours to days.