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Sierra Ledge Rat
Mountain climber
Old and Broken Down in Appalachia
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Oct 30, 2015 - 10:28pm PT
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kpinwalla2
Social climber
WA
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Oct 31, 2015 - 08:48am PT
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Technically the Bighorn slide is mass wasting, not erosion, since erosion involves incorporation and transportation of rock material in a fluid medium such as water, wind, or ice. If you want to witness some world-class erosion, you should get on a plane right now and fly to Oman. Cyclone Chapala is about to make landfall there and some areas are expected to receive 2-3 years worth of rainfall in one or two days. All that water poured that quickly onto one of the driest places on Earth - it's gonna move a lot of silt and sand.
BTW - that "gash" in the Bighorns is called a "sackung" - basically a crack created when a large-scale landslide pulls away from a hill.
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BASE104
Social climber
An Oil Field
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Oct 31, 2015 - 10:30am PT
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Cool. Sandstones are one of my specialties, and a basic principle is that everything above sea level is being eroded constantly. The exceptions being closed basins with accommodation space for sediment to accumulate.
That sandy ground beneath Indian Creek is weathered sand grains from the Wingate Formation, and it is headed down the Colorado River eventually. It would eventually make it to sea level, but there are dams now. Those dams will eventually become mini sedimentary basins. The Colorado moves an incredible amount of stuff every year.
The Glen Canyon Dam will be a waterfall someday. Then it will breach, then you will have something really interesting. Anyway, the dam will not last forever. I haven't calculated the volume of Lake Powell vs. the annual volume of delivered sediment, but offhand, I would guess that it will happen very quickly in geologic time.
Anyway, sand grains are usually quartz grains that originated in granitic rocks. Quartz is very stable chemically, unlike the accompanying feldspars and micas, which chemically weather into clay minerals. Quartz survives, limited only by physical processes. However, the grains can be recycled over and over. The Wingate may come from a predecessor sandstone. The sand deposited from erosion of the Colorado Plateau will someday become a new sandstone and shale assemblage. Generally, that is what happens to sand grains, and they can be deposited as rock, uplifted and weathered again, over and over.
Death Valley has a shale that has glacial dropstones in it. Dropstones are rocks that get stuck in calving glaciers. As they float out into the ocean and melt, very large rocks fall out and find themselves embedded in marine mud. That is very cool, from my point of view, when you see it.
Erosion is a fascinating topic. Geomorphology was one of the most interesting classes that I took. At that time, it was being taught in the geography department, and not even a prerequisite. That baffled me when I saw how important it was to geology. Go figure. The geomorphologist was over in that department.
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thebravecowboy
climber
The Good Places
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Topic Author's Reply - Nov 1, 2015 - 03:26pm PT
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funny how we subdivide geomorph from structure, for sure.
as in:
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McHale's Navy
Trad climber
From Panorama City, CA
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Near Sawmill Pass
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Chalkpaw
climber
Flag, AZCO
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Nov 10, 2015 - 09:01am PT
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Eroding petrified wood along the Painted Desert, between Tuba and Cameron.
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Chalkpaw
climber
Flag, AZCO
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Nov 10, 2015 - 09:12am PT
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Living at the top of the local watershed has all kinds of erosion opportunities. From the house to the west, water drops into Oak Creek and travels south. From the house to the east, water drops into Walnut Canyon and travels north into the Little Colorado. In theory at least. Pits and dams impeedes water doing this at least for the moment.
From the climber's perspective, to the east is priest draw, to the west is Kelly Canyon.
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BASE104
Social climber
An Oil Field
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Nov 10, 2015 - 11:27am PT
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That crack in Wyoming that was posted above is a slump feature.
Gravity always wins, and water runs downhill. Understand that, and you are on your way to becoming a knowledgeable amateur geologist. You can learn a lot with a little reading. Climbers are always taking what for a geologist, would be a field trip. Climbers are pretty smart, and good at identifying differences in rock.
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jonnyrig
climber
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Nov 10, 2015 - 08:33pm PT
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Thanks for the link to that report. Interesting reading. Sort of reminds me of those areas along I80 between, say, Vacaville on down to Berkly, and pretty much most of the ranges in the entire bay area. Incidentally, there are a bunch of layers of weakness up along the Columbia River that have caused some spectacular landslides in the past, and have serious potential in the future as well.
Careful where you put your house, I guess.
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thebravecowboy
climber
The Good Places
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Topic Author's Reply - Nov 12, 2015 - 12:54am PT
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thebravecowboy
climber
The Good Places
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Topic Author's Reply - Nov 12, 2015 - 12:27pm PT
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all those dry (for today) streambeds take that material to the big river when it gets to the valley bottom though. Water, water, water moves. Somehow a saltating grain just ain't as cool as those extensional gashes and the (semi)solid masses of Quaternary material moving, though.
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thebravecowboy
climber
The Good Places
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Topic Author's Reply - Nov 12, 2015 - 12:32pm PT
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Yeah, this earth, it's alright.
some thirsty valley bottoms out your way DMT. kinda envious.
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thebravecowboy
climber
The Good Places
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Topic Author's Reply - Nov 15, 2015 - 07:48am PT
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A fine show of a dramatic topogrqphic inversion. Thanks for sharing!
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StahlBro
Trad climber
San Diego, CA
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Nov 15, 2015 - 09:04am PT
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thebravecowboy
climber
The Good Places
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Topic Author's Reply - Nov 15, 2015 - 09:15am PT
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Stahlbro! Once again you've got me all jelly!
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MisterE
Gym climber
Small Town with a Big Back Yard
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Nov 15, 2015 - 09:42am PT
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Interestingly, erosion is the only naturally-occurring thing that can kill an established slow-growing White Mountain Bristlecone Pine.
There is no cellular degradation - the cells in a 1-year-old tree are exactly the same as on a 3500-year old tree.
Unique in the natural world, I believe.
Cool thread.
Edit for White Mountain alluvial fan coolness we just pulled out of the archive: USFS- shot taken of Lone Tree Creek in 1967
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StahlBro
Trad climber
San Diego, CA
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Nov 15, 2015 - 10:05am PT
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Thanks Cowboy!
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thebravecowboy
climber
The Good Places
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Topic Author's Reply - Nov 15, 2015 - 09:08pm PT
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A great vantage on that fan EW. Envy makes me green.
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