Ecuador's classic waterfall has disappeared

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jmmoxon
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Ecuador's classic waterfall has disappeared

Post by jmmoxon »

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Re: Ecuador's classic waterfall has disappeared

Post by cathalferris »

I haven't yet seen any indication where that flow reappears. That's a fairly large flow of water into a cave that's not immediately flowing where the plunge pool was..

Are there any larger flows into underground systems around the world? I know there are a few streams in counties Clare and Galway that have significant distances underground but not huge flows, certainly not on the scale of this river.

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Re: Ecuador's classic waterfall has disappeared

Post by Franky »

cathalferris wrote:
Sun Apr 05, 2020 4:46 pm
I haven't yet seen any indication where that flow reappears. That's a fairly large flow of water into a cave that's not immediately flowing where the plunge pool was..
Apparently, it flows under the undercutting behind the waterfall, which is now an arch. Actually, I guess the undercutting must have been the exit of a cave, because otherwise there'd have been no space for the rock to collapse into.

From https://science.thewire.in/environment/ ... disappear/:
Now the water falls a few meters behind it, divided into three sections and with a less steep slope. The river flows under an arch that survived the collapse of the land, but from the place where it used to be photographed, it’s as if it never existed.
It's a bit misleading for the headlines to say the waterfall has "disappeared" - it's just moved backwards, which is what waterfalls do. If you look at footage, the new waterfall is almost as impressive as the old one, it's just not visible from the viewing platform:

Last edited by Franky on Mon Apr 06, 2020 12:29 pm, edited 1 time in total.

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Re: Ecuador's classic waterfall has disappeared

Post by Poke »

It looks to me like the entire flow is exiting via the old plunge-pool.

I've seen a few reports saying that authorities don't know "why" it has collapsed - to me it seems really obvious. The waterfall was originally formed by a band of hard (probably igneous?) rock running through much softer conglomerate rocks. Over many years, the plungepool has eaten it's way back under the band of hard rock to a point where there was nothing but conglomerate above it. Water probably started seeping through the conglomerate taking away the sediment which glued it together, and when there was too much weight for what was left to take, it all fell in on itself.

Whilst there is a waterfall in its place in that footage, I think that was taken very soon after the collapse. The lip of that waterfall is over the same conglomerate that washed away, so over time, the angle of the "waterfall" will move further and further from vertical, until it is just a (very) steep rapid. It'll probably happen rapidly at first, then slow over time.

I read a different report that said a hydro scheme upstream could have resulted in sediment settling out of the water before it reached the falls. Water without sediment (apparently) causes increased rates of erosion, so some are blaming the hydro for accelerating the collapse. I can only assume that the reports which say they don't know "why" it collapsed are referring to whether or not the hydro plant was to blame?
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Re: Ecuador's classic waterfall has disappeared

Post by Poke »

Wow. 2 months later and the waterfall has well and truly disappeared. I thought it would happen fast at first, but I didn't think it would be that fast! That is an incredible volume of earth that has been scoured away!



The story is apparently that the erosion has progressed upstream that the associated landslides have severed a major oil pipeline which crossed the river, releasing an unknown amount of oil into the river. A few shots of the pipeline here:



People are understandably annoyed as this outcome wasn't exactly unforseen!
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Re: Ecuador's classic waterfall has disappeared

Post by Chris Bolton »

Thanks for the update, Poke. That new gorge is a serious bit of landforming in progress. I was initially puzzled by "Water without sediment (apparently) causes increased rates of erosion" as I'd expect the opposite, but it lines up exactly with your hypothesis that seepage behind the capstone was the problem. Fresh sediment would be drawn into the seep and keep it blocked, but with no sediment coming down, there's only one way the fines content of the conglomerate can go.

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Re: Ecuador's classic waterfall has disappeared

Post by Mal Grey »

That's astonishingly quick!

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Re: Ecuador's classic waterfall has disappeared

Post by Franky »

Fascinating to watch a geological transformation happening before your eyes. Bits are falling off the banks every second in that video! I wonder how long it will take to "settle down". It certainly looks like an exciting run at the moment!

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Re: Ecuador's classic waterfall has disappeared

Post by jmmoxon »

Possibly now cutting through ash layers (they would erode very quickly), after a lava flow (more resistant) created the original waterfall.
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Re: Ecuador's classic waterfall has disappeared

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Last edited by Mark Gawler on Fri May 15, 2020 9:39 am, edited 1 time in total.
Reason: Fixed image links
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Re: Ecuador's classic waterfall has disappeared

Post by Franky »

jmmoxon wrote:
Thu Apr 09, 2020 9:23 pm
Possibly now cutting through ash layers (they would erode very quickly), after a lava flow (more resistant) created the original waterfall.
My (amateur) hypothesis is that the shoulder of rock from which the waterfall dropped is limestone. That would explain the light hue of the rock (see Poke's second image), and the existence of the arch (limestone being soluble in water). Once the water in the plunge pool had dissolved the limestone all the way through the shoulder, the ash/conglomerate behind it would start to fall away into the gap, and in a short time, the weight of the loose material behind the arch would cause the river bed to start collapsing, backward from behind the limestone shoulder.

Probably a load of ****cks but I thought I'd put it out there.

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Re: Ecuador's classic waterfall has disappeared

Post by jmmoxon »

Difficult to tell on any of the photos / videos what the arch is composed of - it does look fairly columnar...
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Re: Ecuador's classic waterfall has disappeared

Post by Poke »

I'd put my money on Mike's hypothesis that it is igneous rock rather than limestone. I think the river is on the flanks of a volcano, and the angle of the band of rock I think is consistent with lava flowing down from the volcano side. Also amateur hypothesis though! :-)

Whilst they've lost the waterfall as a tourist destination, that arch is pretty impressive... and its got a good story behind it. Could still be as attractive from a tourism point of view. Hope so, for the sake of the local economy!
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Re: Ecuador's classic waterfall has disappeared

Post by Poke »

Apparently the erosion has now reached ~2km upstream.

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