[Brushbuffalo]

Here are a few pictures captured on my "field check" on the Ridley Creek and Park Butte trails, hiked on September 26. Be sure to check out jdk610's blog for some beautiful pictures from her fine run of all of the major trails there, also done on Sept. 26th. More detail will be available in book form when Dave Tucker releases his new book on geology of the Mount Baker area. Watch for it!

Middle Fork of the Nooksack. Virtually all of the surface sediment here was deposited by a debris flow on May 31, 2013. Much more detail here.

Bridge rests on debris deposited in the 2013 debris flow

Trees knocked over by the 2013 debris flow

Rumor is that this was built to shelter judges during the 1911-13 Mt. Baker marathons. Not likely, as such a shelter would have been wiped out in the large 1927 glacier outburst flood from the Deming Glacier.

Poor picture of house-size boulders, now looming in the forest, carried by the Deming Glacier in the latest Pleistocene (deposited about 12,600 years ago)

Only lava flow crossed by Ridley Creek trail. 43,000 yrs. old (old for Mt. Baker itself but relatively young in the Mount Baker Volcanic Field)

Trail from Mazama Park to Cathedral Pass (on right) switchbacks below Cathedral Crag, a single thick basaltic andesite flow some 330,000 years old. A flow of this composition that thick would have been due to ponded lava. Trail is barely visible in this view, but it is good!

Mount Baker and the older remnants of the Black Buttes volcano (note the strata).Colfax Peak (center) and Lincoln Peak (left). View from Tarn Plateau

Survey Point (non-volcanic) and Pocket Lake, a classic small tarn. Looking east from Tarn Plateau, 200,000 year old andesite (I coined 'Tarn Plateau' in my MS thesis, and it has stuck in the geologic literature )

My favorite lookout

North and South (left) Sisters, a large slice of the mantle. Composed of olivine-rich dunite and peridotite. Its glaciers are barely surviving.

Receding Easton (center) and Squak Glaciers(right) from Park Butte. compare 1912. Portions of Deming (far left) and Talum (far right) also show. From Park Butte.

Pre-Mt. Baker basalt, rare in the Mt. Baker volcanic field. Contains green olivine crystals. I had the good fortune to first document this rock in 1976 near Park Butte, but it is much older than I had assumed (about 716,000 years old!), among the oldest lavas to be erupted outside of the Kulshan caldera, and the oldest you will find along a trail in the MBVF.

Note the trail in lower center connecting Mazama Park to Cathedral Pass. The trail from Mazama Park to Baker Pass is north of this (closer to Mt. Baker)

[mbravenboer]

Very interesting! I love that post about the debris flow.

[Sculpin]

[puzzlr]

Thanks for telling us what you see when you look at these landscapes. It's very interesting.

[Brushbuffalo]

[contour5]

Excellent post! Very much appreciate your taking the time to put this one together.

[Brushbuffalo]

[Pyrites]

Are you kidding? Class A report. Better than "I went somewhere. It rained."

[HitTheTrail]

Great post. Rather unique but very informative in a specialized sort of way. Keep it up for other areas of geologic interest. This is a bit off topic, but do any of you guys (or gals) know anything about the specific lithology of the Jurassic Ingalls Terrane (Jis on geologic maps). It looks to me to weather sort of like limestone and looks like a calcareous sandstone or sandy limestone. When I google the term they describe it as nothing like that. They are saying it is ultramafic. Up around Lake Caroline and Mt. Cashmere it is light brown and grussy looking. In fact the slide that came down into Eight Mile Lake are from those rocks and they are light brown. I don't get it.

[Anish]

Great stuff! Park Butte is also my favorite lookout. Thanks for all the information.

[Brushbuffalo]

HitTheTrail, I recall those brown rocks when descending on the trail after climbing Cashmere last year. They appeared to be ultramafic such as we see at the Twin Sisters and Ingalls Peak, as well as other more isolated places. Even though the rocks when freshly exposed are various tones of green, they weather to a rust color when oxidized. If peridotite rather than dunite (which is 90% or more olivine and usually Mg-rich green olivine), then pyroxene varieties such as enstatite and diopside are more abundant, giving the peridotite a brownish or grayish color even before oxidizing. I haven't answered your specific question about the Ingalls terrane, however. [ note, gentle readers, that is not a misspelling of terrain, as in landforms. "Terrane" refers to an assemblage of rocks of vastly different place of origin than where found today. This is plate tectonics in action].

[HitTheTrail]

Yeah, if the official geologic map says so and you say so they must be ultramafic. I was just thrown off by the color and the fact that they weather similar to the way some calcareous rocks weather. Guess I needed to look at them in thin section under a petscope. Thanks.

[Brockton]

Brushbuffalo - That was great, thanks. I'm always interested to learn more about local geology. Even if I don't understand everything, it's fun to read your geological notes along with the stunning photos. I'd love to see more reports like that. Thanks!

[Sculpin]

[Brushbuffalo]