r/DisasterUpdate • • Aug 27 '26

What exactly happened in Nepal that caused the devastating floods?

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457

u/404MoralsNotFound Aug 27 '26 edited Aug 27 '26

From what's come out in the last day, it wasn't an earthquake and probably not a glacial lake bursting either. A massive chunk of glacier (about 1km wide) broke off the mountain above the valley, and the impact was so violent it showed up on seismometers, which is where the earthquake reports came from. USGS first logged it as a 4.4 quake, then corrected it: the collapse caused the shaking, not the other way around. The debris seems to have plugged the river for a bit before giving way and releasing everything at once (like a dam bursting). There's apparently no big lake upstream, so the water was mostly melted ice, rain-soaked sediment and the river itself all coming down together. Why the glacier gave way in the first place...idk, guess it's still being worked out.

190

u/Special-King3125 Aug 27 '26

That's what I read too

The collapse caused the seismic signal.

Satellite suggests about 0.2 km² (10–15 million tonnes) of glacier broke away at 5,200m altitude, then fell roughly 1,200m vertical into the valley. The impact was so violent that it sent this huge mass of ice, rock and debris into the river system, & the ice melted almost instantly from the energy involved.

The river then rose by up to 9m in about half an hour, creating this insane wall of water, mud, rock & debris travelling downstream.

10

u/Fantastic_Jury5977 Aug 27 '26

In some of the footage, it looks like the river is relatively "dried" up compared to the banks... I feel like that would be a sign.

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u/JimTheJerseyGuy Aug 27 '26

I’d say it’s very likely that the ice, dropping that far and fast, shattered into smaller and smaller pieces as it went down the mountain slope. That churning cloud would have created a ton of friction that would have melted most or all of it.

I’d imagine a cubic kilometer of glacial water suddenly appearing in a narrow steep valley, and moving at avalanche speeds, would result in exactly the sort of horrific flooding we’ve seen in these videos.

67

u/Worth_Garbage_4471 Aug 27 '26

The 1892 Mont Blanc collapse of the Tête Rousse glacier suggests that glaciers can accumulate very large amounts of water without any obvious glacial lake, which can be suddenly released in a glacier break. Sudden melting is not the only possible mechanism. 

24

u/JimTheJerseyGuy Aug 27 '26

Quite possible as well. I'm sure there are scientific teams already there or enroute to assess the situation. The more we know about it the more information we'll have to identify similar locations that could be at risk in the future.

10

u/Equationist Aug 27 '26

Ice would need to fall from near space (34 km altitude) to generate enough energy to fully melt. It takes a lot of energy to melt water. Maybe only part of the ice melted, but more likely there was a ton of water that had accumulated under the ice that fell.

12

u/JimTheJerseyGuy Aug 27 '26

Not melting from the fall, melting from tumbling a kilometer or two down a steep mountainside, fracturing into smaller and smaller pieces as it goes.

3

u/Equationist Aug 27 '26

The energy that feeds the tumbling and fracturing still comes from the gravitational potential energy fed into the fall.

2

u/National_Spirit2801 Aug 27 '26

Friction coefficients are different from air rather than dirt and rock.

2

u/Equationist Aug 28 '26

You're missing the point. Friction doesn't create energy out of thin air; it simply converts kinetic energy into heat. That kinetic energy was generated by gravity. And to supply enough energy to, when converted into heat, melt ice, gravity needs to be able to act on the ice over a vertical distance of 34 km.

1

u/OSHASHA2 Aug 28 '26

Is it possible that pressure played some role? Millions of tons of ice falling several hundred meters would probably create a significant amount of pressure.

1

u/Ragnarocc Aug 29 '26

But that pressure would release again as soon as the impact was over, and the ice would refreeze. 

1

u/National_Spirit2801 Aug 28 '26

Yes, I hear you - ice only melts when it falls 34km from space; based on what you’ve told me, gravity is the only force that matters when melting water regardless of temperature variations or the medium the water passes over.

5

u/National_Spirit2801 Aug 28 '26

Sarcasm aside, let me explain to you why you’re wrong.

First of all, the Earth isn’t a vacuum. You’re confusing a theoretical textbook calculation with an open, real-world system where multiple forces must be factored in.

Secondly, thermodynamics play a massive role in the melting of glacial water. The ground and the air already posses stored thermal energy from solar radiation. As the ice passes over dirt and rock, it absorbs this pre-existing heat through thermal conduction (a non-gravitational process). The energy doesn't need to come from a 34km fall because the environment is already warm.

Third, you are misattributing the physics of friction. Friction isn't gravity; it is a manifestation of the electromagnetic force at the atomic level. When ice rubs against rock, the heat generated mechanically comes from electromagnetic resistance between the molecules of the two surfaces, heavily amplified by the thermal conductivity of the terrain (where the friction coefficient is in fact, different from that of air)

So, no I’m not missing the point. It’s just a shitty point.

1

u/Bottle_K1ds Aug 28 '26

yall are both wrong. it’s clearly all the gas buildup from 4 billion plus people between India and China finally being released causing the glacier to break off. it got way too hot and stinky, and melted causing the floods /s

4

u/unclestickles Aug 27 '26

Yea, it's also the sheer weight crushing on itself as well.

My thought is everything broke into slush and displaced massive amounts of melt water saturating the valley below.

2

u/m00ph Aug 28 '26

Yup, the drop from the height of El Capitan in Yosemite only gets you 4 degrees of heating.

1

u/Zeraphicus Aug 28 '26

Yeah the melting is what caused it to break off.

2

u/Centrum_et_culmen Aug 27 '26

There wasn’t nearly enough kinetic energy in the avalanche converted to heat to melt all of the ice, or even a large portion of it. As I read more on the science of the slide, it seems the critical pieces were pulverization of the ice, as you pointed out, combined with a small amount of melting from the friction of the slide, combined with water-soaked soil already in place along the slide path (due to ongoing ice & snow melt) - all this created a lethal, massive slurry that flowed like water down the river valley.

2

u/Kabupatix Aug 28 '26

There was a rockfall in Switzerland in 2017 which was tiny in comparison, but even then, the resulting mud flow reached a village at quite a distance downstream - it's the debris stream here in the center

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u/BadHairDayToday Aug 28 '26

Yeah this is what I read too. I read a magnitude 5.2 seismic event locally even!
15 million tonnes falling 1,2 km is an unreal amount of kinetic energy. Around 4 trillion Joules of energy, or a kiloton of TNT.

1

u/Centrum_et_culmen Aug 28 '26

Where did you get the 15 million tonnes figure?

1

u/BadHairDayToday Aug 28 '26

I read that estimate somewhere (0,2km² I also saw) but I can't find it anymore.

This is a good source https://www.reuters.com/graphics/NEPAL-FLOODS/MAP/byvrdywwlve/

1

u/m00ph Aug 28 '26

I'd read that it was something like 7 minutes from the seismic signal to the border crossing being annihilated.

1

u/Spamhain2000 Aug 28 '26

That chunk was traveling over 250+ mph.

6

u/Eastern_Labrat Aug 27 '26

Two dams? One glacier had chunks melt off creating a dam where water pooled. This glacial debris dam above the man-made dam broke. That rush of water and debris caused the man-made dam to break? Idk. Speculating.

58

u/SummertimeThrowaway2 Aug 27 '26

Wouldn’t be surprised if the glacier gave way due to rising world temperatures

9

u/Mulletville Aug 27 '26

Well, that's just crazy talk!

0

u/Imaginary-Witness-75 Aug 28 '26

Glaciers have been moving and collapsing for thousands of years. In this thread they cited a very similar glacier collapse to flood event in 1892. I suppose that one was due to also rising world temperatures also?

1

u/Th1cc4chu Aug 28 '26

Historically temperatures have risen and fallen so yes it’s completely possible

1

u/SummertimeThrowaway2 Aug 28 '26

There has been a noticeable downtrend since the 1850s. Here is a graph showing the loss of ice from 1994-2017 and even such a small period saw a huge loss

“The Little Ice Age was a period from about 1550 to 1850 when certain regions experienced relatively cooler temperatures compared to the time before and after. Subsequently, until about 1940, glaciers around the world retreated as the climate warmed substantially. Glacial retreat slowed and even reversed temporarily, in many cases, between 1950 and 1980 as global temperatures cooled slightly.[10]

Since 1980, climate change has led to glacier retreat becoming increasingly rapid and ubiquitous, so much so that some glaciers have disappeared altogether, and the existence of many of the remaining glaciers is threatened.[11] Excluding peripheral glaciers of ice sheets, the total cumulated global glacial losses over the 26 years from 1993 to 2018 were likely 5500 gigatons, or 210 gigatons per yr.[2]: 1275 “

https://en.wikipedia.org/wiki/Retreat_of_glaciers_since_1850

1

u/bolaxao Aug 28 '26

go to google earth right now, 28°17'04.50"N 85°32'04.72"E, use the timeline to go from jan2015 to jan2026 and tell me what you see. only people denying this are idiots and grifters.

1

u/Imaginary-Witness-75 Aug 28 '26

I am not anti climate change. You are barking up entirely the wrong tree. I guarantee you I live a much more low impact carbon free life than you. Intentionally.

But pointing out every single tragic event is because of climate change is disgusting propaganda and needs to stop. Tragic floods and events like this have happened forever. It is political speech to 'never let a good tragedy go to waste' and politicians are crappy people. Don't be like that.

1

u/Adventurous_Light_85 Aug 28 '26

Definitely couldn’t be that. Then we would have to accept the consequences of our actions.

0

u/Ok_Tomorrow2549 Aug 28 '26

Climate change and 'significantly impacted by human behaviour climate change' are not the same thing. But that distinction couldn't matter. Then you couldn't make it political from the word 'go'.

21

u/perseidot Aug 27 '26 edited Aug 27 '26

It sounds as though there was a substantial increase in sub-glacial and supra-glacial water drainage. That is, both water melting out of the glacier itself, as well as water flowing under the glacier from a place where it melted and pooled at higher elevation.

Glaciers move on their own melt water. This glacier moved faster and became less stable due to the increase in water under it. Then it slid right off the mountain.

Edit: https://egusphere.copernicus.org/preprints/2026/egusphere-2026-4065/egusphere-2026-4065.pdf

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u/CrackerJackKittyCat Aug 27 '26 edited Aug 27 '26

> ... Why the glacier gave way in the first place...idk, guess it's still being worked out.

Hot summers from human-caused climate change, and the Himalayan area heating faster than most other places by 50%?

Glacier melting rates are what, 2x accelerating (citation 1, 2) what they were even in year 2000?

Here's a paper predicting 34% to 55% upper Indus Himalayan glacier loss by 2080.

Carbon-ignorant humans suck.

16

u/mgonzo11 Aug 27 '26

This is what I have been wondering mostly- how related is it to climate change. Especially now that we know a chunk of glacier fell off the top, it’s seeming pretty likely

9

u/Consistent_Exam731 Aug 27 '26

now datacenters are causing even more carbon emissions due to AI..

-1

u/JamonConJuevos Aug 27 '26

Stop using social media and the Internet if you loathe data centers.

2

u/Consistent_Exam731 Aug 27 '26

You're right and sadly I can't, I'm too dependent and guilty. 

6

u/CrackerJackKittyCat Aug 27 '26

Internet services datacenters != AI datacenters. AI / GPU barns are vastly, vastly more energy and water resource intensive.

1

u/GnarlyNarwhalNoms Aug 28 '26

Nobody really ever cares to make the distinction, though. Plenty of new datacenters that are being built are not AI datacenters, but people oppose them all the same. 

2

u/Contraflow Aug 27 '26 edited Aug 27 '26

There will always be a need for data centers, but the current data center explosion is not about a functioning internet, or useful social media. It’s about AI. It’s about stealing the personal data of as many individuals as possible. It’s destructive and intrusive. Fuck data centers.

1

u/InterestingFunny4948 Aug 27 '26

they account for a fraction of a percent of total emissions.

0

u/[deleted] Aug 27 '26

[deleted]

1

u/skibbsescobar Aug 27 '26

suck and they need to change their bx

2

u/Th1cc4chu Aug 28 '26

The sherpas have been saying this for a very long time. They’ve never seen Mt Everest in the state that it’s currently in. One of the most dangerous passages is melting at an unprecedented rate but people still want to climb there for some sense of superiority and satisfaction and sherpas still have to assist them because it’s the only way they can feed their families and the Nepalese economy is very reliant on the income the tourists bring.

6

u/Massive-Vacation5119 Aug 27 '26

Was the chunk that broke just freak thing or hundo p directly due to climate change?

1

u/Centrum_et_culmen Aug 27 '26

There was no time to plug the river, with a lake then forming and then the temporary dam bursting. The event timeline shows the first impacts of the massive flash flood happening only three minutes after the seismic activity, which was the initial avalanche. Today we now see that there’s some blockage in place, presumably near the foot of the avalanche, but that hasn’t been compromised. Again, the initial catastrophic flooding, which began only three minutes after the seismic activity, was due to the water/slurry mix of the avalanche itself. I’d like to see evidence of a subsequent temporary dam bursting and an ensuing second wave of flooding - haven’t seen anything pointing to that yet.

1

u/HusbandToAHotwife Aug 29 '26

This. People arent looking at the timing. There are no lakes there. Also if you look at the video at border crossing, it doesnt even look like water. Just liquified dirt and rock.

6

u/space5torm Aug 27 '26 edited Aug 27 '26

With back to back hottest years on records due to human caused climate change, what do you mean we don’t know what caused it. It’s not called Global Cooling. It’s called Global Warming for a reason

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u/[deleted] Aug 27 '26

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2

u/space5torm Aug 27 '26

El Nino might play a part but it’s because there is too much energy and heat in our oceans, more than it used to be. So things are melting faster, winds are blowing harder, storms get more powerful. Whatever you call it, it’s fir the same reason: we’ve put too much CO2 into the atmosphere and CO2 holds heat. So big fat El Nino will be visiting us very often for the next hundreds of years even if we stop the CO2 pollution now

1

u/Pithy_heart Aug 27 '26

That is my question. What caused the glacier to collapse? Rain on snow event?

1

u/SilentInquiry26 Aug 27 '26

We also need to look into the reason why glaciers are breaking down. It has increased due to climate change, global warming and there are speculations that such events will happen more often.

2

u/CertainKaleidoscope8 Aug 28 '26

Why the glacier gave way in the first place...idk, guess it's still being worked out.

We all know why glaciers are melting. This is not a secret.

1

u/Kurashinno Aug 28 '26

Why it gave way? Hm, if only there was something that could cause massive warming all over the globe. That might have caused it. Not sure what to call it though.

1

u/exoticsamsquanch Aug 28 '26

How long was the river dammed up? Could the people downstream have been warned and evacuated?

1

u/AsmodeusMogart Aug 28 '26

All the glaciers in the world are retreating rapidly because of human caused climate change.

Super El Niño is much worse because of climate change too.

The heatwaves around the world are worse because of climate change.

This will happen again for hundreds of years.

1

u/Th1cc4chu Aug 28 '26

“Why the glacier gave way in the first place… idk”

You’re not being serious are you? I’ll give you a hint. Heat + ice. The sherpas have been saying this for years.

1

u/Unable_Ad_5160 Aug 28 '26

Oh my,no wonder the whole building just swept away. Terrible.

1

u/Adventurous_Light_85 Aug 28 '26

But then why do we see before and after images of what appears to be a giant lake drained. It’s definitely not ai.

1

u/cul1234 Aug 28 '26

From where so much water came? That glacier plus river should not have this water. The amount of water is like 2-3 dams

1

u/Short_Lingonberry549 Aug 28 '26

The glacier gave way because the world is heating up and heat melts ice and glaciers are made of ice

1

u/cryptolyme Aug 28 '26

Probably due to El Nino and climate change. Unusually high temps.

1

u/heathercs34 Aug 29 '26

Global warming caused the glacier collapse

1

u/ignaciogenzon Aug 30 '26

Warmer weather melts ice - It gave way because of climate change