Mud Flood
March 7, 2019 4:14 PM Subscribe
A group of trackers on the flanks of Aconcagua in Argentina experienced a spectacular debris flow.
It starts slowly, but hang in there!
HOLY CRAP. I’m so glad that guide was familiar with the sound of an approaching surge, else this video would be hosted on LiveLeak.
posted by ejs at 4:36 PM on March 7, 2019 [6 favorites]
posted by ejs at 4:36 PM on March 7, 2019 [6 favorites]
Me watching the video: "Well, that river of rocks sure looks odd, I could watch it all day, but I don't think I'd call it spectacu... WHOA! SHIT!"
posted by ardgedee at 4:54 PM on March 7, 2019 [2 favorites]
posted by ardgedee at 4:54 PM on March 7, 2019 [2 favorites]
That’s pretty terrifying. I’m super glad nobody died because it sure seems like that wasn’t very far from happening
posted by aubilenon at 5:05 PM on March 7, 2019 [5 favorites]
posted by aubilenon at 5:05 PM on March 7, 2019 [5 favorites]
How much water is in that? What is it how does it happen give me science about it. I beg you.
posted by vrakatar at 5:15 PM on March 7, 2019 [1 favorite]
posted by vrakatar at 5:15 PM on March 7, 2019 [1 favorite]
Whoof.
If you click through to the AGU link there's more of that debris channel, and then in the sidebar there's a whole rank and file of related AGU topics. E.g. "an interesting, disruptive landslide" on 101 in Oregon, which is quite a peaceful small problem compared to the huge landslides near dams in various parts of the Himalayas.
posted by clew at 5:16 PM on March 7, 2019
If you click through to the AGU link there's more of that debris channel, and then in the sidebar there's a whole rank and file of related AGU topics. E.g. "an interesting, disruptive landslide" on 101 in Oregon, which is quite a peaceful small problem compared to the huge landslides near dams in various parts of the Himalayas.
posted by clew at 5:16 PM on March 7, 2019
Vrakatar, the AGU post comments are wondering that too -- the `nose' of the flow is dry, pushed by a bulge of wet heavy mobilized material behind; but also the sides of the channel seem very damp, so maybe the flow at the beginning is the tail of an earlier wet flow.
posted by clew at 5:17 PM on March 7, 2019 [2 favorites]
posted by clew at 5:17 PM on March 7, 2019 [2 favorites]
(Not the comments, the text of the post, sorry.)
If you want more science, the Landslide Blog links to all the papers from Triggering and Propagation of Rapid Flow-like Landslides – The Proceedings of the Second JTC-1 Workshop, online free. Largish PDF.
posted by clew at 5:20 PM on March 7, 2019
If you want more science, the Landslide Blog links to all the papers from Triggering and Propagation of Rapid Flow-like Landslides – The Proceedings of the Second JTC-1 Workshop, online free. Largish PDF.
posted by clew at 5:20 PM on March 7, 2019
Better, here's a blog post from Geological Digressions with simple diagrams explaining why wet material flows more than dry does (v useful pictures, and a tiny experiment that You can Do at Home).
posted by clew at 5:34 PM on March 7, 2019 [2 favorites]
posted by clew at 5:34 PM on March 7, 2019 [2 favorites]
The AGU video collection is amazing. Some of those are scary.
posted by Dip Flash at 5:37 PM on March 7, 2019
posted by Dip Flash at 5:37 PM on March 7, 2019
I was wanting to scream at the video, when the guides are still escorting people across the debris flow. I mean, yeah, they have way more experience than me, but if I saw part of the dirt of the mountainside begin to flow, there’s no freaking way I’d just step across it.
They were literally only about five seconds away from getting someone killed, dragged down the hillside under tons of flowing mud. Sheesh.
posted by darkstar at 6:07 PM on March 7, 2019 [4 favorites]
They were literally only about five seconds away from getting someone killed, dragged down the hillside under tons of flowing mud. Sheesh.
posted by darkstar at 6:07 PM on March 7, 2019 [4 favorites]
that was amazing to see the guide snap into action.
posted by biggreenplant at 6:11 PM on March 7, 2019 [2 favorites]
posted by biggreenplant at 6:11 PM on March 7, 2019 [2 favorites]
that landslide blog is serious rabbitholing material
posted by thelonius at 6:54 PM on March 7, 2019 [2 favorites]
posted by thelonius at 6:54 PM on March 7, 2019 [2 favorites]
How do these things even work? How can they happen if the slope of the mountain isn't above its angle of repose, which I thought would be impossible?
posted by Joe in Australia at 8:35 PM on March 7, 2019 [1 favorite]
posted by Joe in Australia at 8:35 PM on March 7, 2019 [1 favorite]
Also, this is totally the Sambatyon, which is a
river resembling a fortress, which contains no water but rather rolls sand and stones with great force. If it encountered a mountain of iron it could undoubtedly grind it into powder. On Friday, at sunset, a cloud surrounds the river, so that no man is able to cross it. At the close of the Sabbath the river resumes its normal torrent of stones and sand.posted by Joe in Australia at 8:43 PM on March 7, 2019 [3 favorites]
Well, this is all new to me. The article about the San Gabriel Range and the debris basins, the giant boulders downtown that is amazing.
posted by Oyéah at 9:08 PM on March 7, 2019 [1 favorite]
posted by Oyéah at 9:08 PM on March 7, 2019 [1 favorite]
If you liked the Aconcagua debris flow, you'll love the debris flows at Illgraben in Switzerland, which are so frequent that there's an alarm system and a series of concrete dams to slow and channel the flows. (Video starts gently but you can hear the rumble of the approaching boulders and the main flow becomes visible at 1:00.)
posted by cyanistes at 2:59 AM on March 8, 2019 [6 favorites]
posted by cyanistes at 2:59 AM on March 8, 2019 [6 favorites]
Thanks for sharing! I saw that second video a few years ago and a while back had tried to find oit again but couldn't.
Debris flows are really cool. They're what really carved Grand Canyon. I mean, yeah, it wouldn't exist without the Colorado River, but the Colorado river is primarily responsible for carving the depth of Grand Canyon. All that width? That's debris flows. They move the rock down to the Colorado River, and the Colorado River moves that rock down toward the Gulf of California.
Grand Canyon is a massive collection of smaller individual drainages that feed into the river. These drainages may contain a stream that flows at a few hundred cubic feet per second, or normally contain no water at all. This is in comparison to the Colorado River, which today flows at around 10,000 cfs, and during ice age times would have had regular seasonal flows as high as 500,000 cfs. And yet, drainages that are dry for 99% of the year have cut side canyons down to the same depth as the Colorado River itself. How is that even possible?
Debris flows are the answer! The steep grade from rim to river means that these debris flows move fast. I've read that the maximum particle size that can be carried by water scales in proportion to the sixth power of its velocity. So when water gets moving fast, the rocks it carries get REALLY big REALLY fast. All those fast-moving giant rocks in a debris flow do an awesome job carving canyons. So there you go. Debris flows are neat.
posted by compartment at 8:23 AM on March 8, 2019 [7 favorites]
Debris flows are really cool. They're what really carved Grand Canyon. I mean, yeah, it wouldn't exist without the Colorado River, but the Colorado river is primarily responsible for carving the depth of Grand Canyon. All that width? That's debris flows. They move the rock down to the Colorado River, and the Colorado River moves that rock down toward the Gulf of California.
Grand Canyon is a massive collection of smaller individual drainages that feed into the river. These drainages may contain a stream that flows at a few hundred cubic feet per second, or normally contain no water at all. This is in comparison to the Colorado River, which today flows at around 10,000 cfs, and during ice age times would have had regular seasonal flows as high as 500,000 cfs. And yet, drainages that are dry for 99% of the year have cut side canyons down to the same depth as the Colorado River itself. How is that even possible?
Debris flows are the answer! The steep grade from rim to river means that these debris flows move fast. I've read that the maximum particle size that can be carried by water scales in proportion to the sixth power of its velocity. So when water gets moving fast, the rocks it carries get REALLY big REALLY fast. All those fast-moving giant rocks in a debris flow do an awesome job carving canyons. So there you go. Debris flows are neat.
posted by compartment at 8:23 AM on March 8, 2019 [7 favorites]
Joe in Australia, a slope can be steeper than its angle of repose because mountains aren't made by dribbling separate rocks from above, they're made by shoving blocks of material up from below. Then the blocks shatter or weather into separate rocks/particles, and *then* the angle of repose is relevant, but (a) rocks can be temporarily balanced together, like a wall (b) roots can hold them together and also force them apart (c) the angle of repose is lower in saturated material (d) rain or animal movements can shift a few particles free and the movement of small ones can start the movement of large ones, like an avalanche (e) &c.
tl;dr McPhee, as above. Or check out textbooks on geomorphology.
posted by clew at 3:03 PM on March 8, 2019 [2 favorites]
tl;dr McPhee, as above. Or check out textbooks on geomorphology.
posted by clew at 3:03 PM on March 8, 2019 [2 favorites]
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