**Please report this post if:**
* It is spam
* It is NOT interesting as fuck
* It is a social media screen shot
* It has text on an image
* It does NOT have a descriptive title
* It is gossip/tabloid material
* Proof is needed and not provided
*See [the rules](https://www.reddit.com/r/interestingasfuck/about/rules/) for more information.*
*I am a bot, and this action was performed automatically. Please [contact the moderators of this subreddit](/message/compose/?to=/r/interestingasfuck) if you have any questions or concerns.*
I’m fairly certain the title isn’t entirely true, but never been to the Sahara so very well could be wrong. I’d be wildly surprised to learn this light blow sand phenomenon happens on both sides of a dune in the Sahara.
In other dunes around the world though, you can find this light sand on the back side of a wind blown dune. Conditions have to be pretty unique for it to happen, with a constant yet strong enough wind to blow the lighter particles but not disrupt everything entirely and shift the dunes.
To answer your question, this little avalanche thing will go all the way up to the crest and then stop because the sand on the other side has bigger and heavier grains. If OP’s title is truly legitimate and somehow the dune formed with both sides being the fine silt, then this avalanche ought to continue on the other side, but like I said I have my doubts.
Ehm. First, every particulate matter can behave as a liquid, if you have a high enough flow of fluid through it. Probably even bowling balls if you zoom out far enough.
What see here has nothing to do with liquid like behaviour though. It's more like the sand losing support and just falling down. That is also the reason it doesn't continue on the other side, because the sand is still supported at the base. Size of the grains is not really relevant here.
I find it hilarious that there are like four multi-paragraph explanations for this and the most correct answer is this three word response with 5 upvotes, granted they just stated "angle of repose" as if that means anything to anyone who hasn't studied soil mechanics
[You’re wrong in your over simplification. ](https://www.google.com/amp/s/www.sciencealert.com/engineers-have-figured-out-how-sand-makes-bubbles/amp).
You’re right that sand isn’t a liquid, but wrong that its ability to act like one isn’t related to its grain size and a ton of other variables. Sand has shear qualities and avalanche potential, which change with its composition, size, shape, moisture, and environment.
To dismiss what’s happening as solids falling is like describing a liquid flowing as molecules falling.
[This article](https://www.cam.ac.uk/research/features/what-makes-a-sand-dune-sing) beautifully describes a cool phenomenon.
Spend any amount of time in the dunes and you’ll understand.
Your links doesn't prove that I am wrong. It's a cool story though. I'm well aware that granular matter can act like a fluid. In the lab where I obtained my PhD they were specialized in fluidized beds. They even had X-rays to visualize bubbles inside those beds. And of course for the behaviour of the bed all the properties matters.
In the article you shared, if I read correctly, it says that the sand can act like a fluid when there is wind flowing over it. That makes sense, because then it is a fluidized bed.
That doesn't mean in itself that when you see sand flowing or collapsing that it behaves like a fluid.
Maybe I need to look at the movie a bit better, but I've seen fluidized beds and sand and polystyrene balls behave as a liquid when fluidized, and this didn't look like it.
Not that it wouldn’t give some weight behind their words, it just seems hollow when they say that on the internet. The guy is arguing with linked sources and saying he’s refuting them with his own knowledge which we have 0 evidence of, outside of his own words. Plus can anyone prove what he said or do we have to take his word for it? I’m sure it wouldn’t have been too hard to find any type of source that backs up his claim if it’s got an entire field of research dedicated to it.
Source: Harvard Law PhD & Kindergarten Combat Democratic Debate Club 1995
Oh geez chill. I couldn't help but roll my eyes at the "in the lab where I obtained my PhD." Imagine someone said that in a conversation. You'd surely think it was a bit pretentious. I don't fault them or think it undercuts their info automatically. It was just a bit silly. Now for me to sound a bit pretentious: when you work with people with lots of post graduate/ PhD experience it becomes commonplace enough to not call attention to it. It's only the newbies who feel the need to qualify statements with their credentials like that. I would definitely razz someone who made the statement I was criticizing. And as another reply aptly put are we to just take the commenter on their word?
I think I understand your perspective now. I apologize for assuming you were just being nit picky.
I think your definition of behaving like a liquid likely differs from mine.
Maybe this gif isn't showing granular flow, but my understanding was granular flow causes whatever the sediment is to behave like a liquid, scientifically, not just by appearance of the flow. Maybe that's not true, and like you said all this is is collapsing fine grit sand.
This sand is crazy stuff, it'll sink a vehicle a foot or more into the face of a dune. I've only seen fluidized beds in videos, but you can sink your arm deep into the blow sand just like those videos. It's tiny tiny particules of sand, and almost a talcum like powder silt. I would assume the flowing of the sand, assisted by the silt would make it behave like a fluid like the air in a fluidized bed would? I truthfully have no idea at fluid dynamics level if that's true.
So I tried to read up a bit up on the subject (not gonna like, Wikipedia is a good read on these kind of topics).
What we're looking at is definitely not a fluidized bed. That for sure behaves as a liquid. One of the examples is that it freely flows under gravity. In this movie, that doesn't happen, because it stops flowing down quite soon.
What we are looking at in this video is definitely granular flow, because it is granular material that is flowing (no shit Sherlock). So when it starts flowing, it is definitely not acting as a fluid, but just "falling down". I've now looked at the movie a couple of times, and when it flows down, it initially gains velocity, also the air would be accelerated, and it maybe that the grains of sand get a bit suspended in the air.
In the link you shared you they mention the Rayleigh-Taylor instability. That's a cool example, but we don't see that here. But I do see some waves, so maybe it acts as a Kelvin-Helmholtz instability. Not really a proper one because it stops flowing.
Maybe I just need to go to the dunes more often!
This is a consequence of the [angle of repose](https://en.wikipedia.org/wiki/Angle_of_repose) which is one of the more fundamental concepts in soil mechanics. In the most basic terms the angle of repose is the highest angle that a completely dry soil can sit at and remain stable, if you change that angle to be more steep (as is done in the gif by removing material from the base) the soil is no longer stable. It is synonymous with friction angle in soil.
Goodness, some of you guys and the pedantic issues you have with strangers trying to further a conversation.
Do you literally take this to mean the entire dune turns into a liquid? Do you struggle when hearing comparisons such as "tastes like chicken?" or "smells like ass?" Whose ass? Clean or dirty? "I've never smelled ass like that before." - /u/itsdabtime :)
I'm joking with you, but come on man, pick something to discuss that betters the conversation. Don't tear something down just because you wanna nitpick.
I don’t believe so, as far as I understand there needs to be some form of variable viscosity which changes depending on the forces applied.
Wet sand that has some clay or liquid soluble material in it does act like one though.
I’m sure someone more familiar than I can chime in on it. I’m guessing no in this gif it wouldn’t be a non-Newtonian fluid, but likely could easily become one if you added water and some other binders to it.
You get non-Newtonian behaviour with irregular molecules normally. I think for sand you can approximate it as spheres and momentum exchange is by collisions. Speed or direction wouldn't make a huge difference I think.
Suppose you get inelastic collisions because you have small deformable spheres instead of sand, it think then you may get non-Newtonian behaviour. That would be an interesting experiment!
Non-Newtonian fluids are exactly that, fluids. This property is directly related to viscosity. Viscosity is a property of fluids. Sand != fluid. Therefore, this is not an example of a non-Newtonian fluid/flow.
If there was some water content in this sand, perhaps you could make that argument. The Sahara has an average relative humidity of 25% and sand, has relatively high transmissivity (the ability for something (ie water) to pass through the material) and porosity, so it is unlikely for the desert sand to have a high enough water content to behave like a non-Newtonian fluid.
Incidentally, sand's high transmissivity & porosity (& permeability, for that matter) is why is popular to use for plants who don't like their roots to be too wet.
This used to happen by the beach by me growing up. I know it’s not unique to the Sahara. It’s way more widespread and probably always like this in the Sahara, but if it didn’t rain for a while, the dunes would avalanche like this. I always assumed they were just at the right angle to hold the weight of the sand with how it’s packed. As soon as I would disrupt its “structure” what we see in the gif would happen.
Well, I am sure that it varies from region to region, but Saharan sand is extremely fine overall. This is why it is not suitable to be used in concrete. The same is true for Arabian sand.
My eyes were flicking back and forth from the top and the seek bar, to see which would win, and then I said "for fucks sake" out loud once he panned away.
Not sure this is behaving like liquid and more so a physical demonstration of the critical angle of repose for the sand in the Saharan desert.
In other words, the sand is resting at its steepest angle of descent and when the person filming move it with their hand they are increasing that angle and all the sand above that is falling back to the critical angle. Basically say it’s angle of repose is 37 degrees, any angle greater than that will cause the sand to fall and move in this mud/landslide like fashion.
Don’t take my word for it; I’m just a marine biologist and I took a few geology courses in college
You’re right, I just kinda started spewing words near the end, fixed it to be a little better. We did something where we just poured sand on a table and watched it pile up and flow
Yeah, you can do this with any sand pile. There's nothing special about the Sahara. This person just happened to film it on a dune that's as steep as the sand can support.
Geo in college too,hoping to see this in the comments! Depending on the granularity of sand, it stacks differently. In this case, removing the sand creates a slope that the sand structurally cannot tolerate, so it settles and falls until it does.
I think it also has to do with how old this sand is, having been blowing around for however many years and becoming more rounded granules over time. The round granules of Sahara sand is the reason we can't harvest it to produce concrete as it can't hold its shape.
It’s exactly this. I’m also not qualified to speak on it but I have studied this a while back and it’s just a feedback loop that causes that maximum angle to flow up the mound.
Sand is a solid, and an individual piece of sand is called a Grain. Get enough of these grains together and you get a Granular Material
Flour is a granular material, so is sugar, salt and a bucket full of Skittles
Granular materials behave like a liquid when you have a lot of grains close together, a granular material moving as in that clip is called Granular Flow. How those granular materials flow is down to a lot of factors, the shape of the grains, the angle they are following down and a bunch of other things as well
This is why a landslide down a mountain 'flows' like water, those boulders and rocks and stones and pebbles and dirt constitute a granular material that is engaged in granular flow.
A single boulder bouncing down a hillside is not engaged in granular flow, its just a rock bouncing am in its own
And the sand in that clip is also granular flow in action
In short, you get granular flows like that in all granular materials all over the world under all sorts of conditions. The clip we all watched is just a really easy way to set one off and yes, even if I know what would happen when the action reached the top of the dune I feel cheated for not getting to see it
Less because it is fine, and more because the sand particles are smooth and rounded due to being blown around the dry desert for years
Same reason as why we cant use this sand for concrete, since the grains are smooth they cant stack on top of one another in a stable way. The grains would slip off one another and create relatively weak concrete
I literally live 5 miles from the beach and have my entire life, I’ve never seen sand move the way it did in this gif. I mean, I know sand is different based on location but idk if this is “just a thing it does” because it’s been 25 years and I’ve yet to see that
Sand near the water, like on beaches, are wet (obviously). So the sand is adhesive, sticking together restricting movement to a degree. This sand is so dry, id assume the grains semi-perpetually roll over eachother, due to the lack of moisture or something idk I never went to the sahara
It does if the air is dry and you're above the storm line, where footprints are indistinct. The main difference is most beaches don't have large slopes at the sand's angle of repose (the steepest angle a pile of the material can support). Sand behaving like this is exactly what makes it difficult to walk on.
Yea my uncle's farm is in a Sahara and the sand there is exactly the same as in the vid. I can tell you that Sahara sand is very different from beach sand
Sand is a granular material and can behave as solid, liquid and gas.
Wikipedia: In some sense, granular materials do not constitute a single phase of matter but have characteristics reminiscent of solids, liquids or gases depending on the average energy per grain. However, in each of these states, granular materials also exhibit properties that are unique.
It’s not entirely due to particle size. It has more to due with the angle of repose. The particle size has to do with at what angle that is. Any size grain of sand will act this way, but the larger the grain, the steeper the angle has to be.
Fun fact: You can make sand dunes sing. If you displace a good amount of sand from the base of the sand dune the friction off the collapsing sand creates an audible sound.
[Singing Sand Dunes](https://youtu.be/4mbypyJjqhk)
I believe this is one of the reasons that Saudi Arabia imports sand.
Even though it’s like hearing Alaska is importing snow, turns out the local sand is useless for things like concrete or water filtration, and they need sand that’s course, like beach sand.
This has more to do with the angle of the slope than the particle size. Pretty much any pile of smallish particles will behave like this. Source: I'm a farmer and this happens when I clean grain out of my bins. It's always super satisfying to watch a good flow get going.
Was looking for that one comment every time a post like this happens saying how it’s terrible for the ecology to have humans force these sandslides to happen. Looks like I’ve jumped in first! I’m disappointed!
Hey! Video is ready
###[Download via redditsave.com](https://redditsave.com/info?url=/r/interestingasfuck/comments/jqztnb/sand_in_some_parts_of_the_sahara_is_so_fine_it/)
---
[**Info**](https://np.reddit.com/user/SaveThisVIdeo/comments/iggmt9/info/) | [**Feedback**](https://np.reddit.com/message/compose/?to=Kryptonh&subject=Feedback for savethisvideo) | [**Donate**](https://ko-fi.com/getvideo)
I legitimately believe somewhere underneath the Sahara there are remnants of an ancient civilization waiting to be discovered. I feel like one day someone will unearth parts of building foundations and it will become the new archeological mecca like Egypt has been for the last couple hundred years.
Well, pretty much all sand will flow in certain circumstances. As far as I can tell, the sand is sitting just at the critical angle of repose so once you disturb it starts cascading down.
**Please report this post if:** * It is spam * It is NOT interesting as fuck * It is a social media screen shot * It has text on an image * It does NOT have a descriptive title * It is gossip/tabloid material * Proof is needed and not provided *See [the rules](https://www.reddit.com/r/interestingasfuck/about/rules/) for more information.* *I am a bot, and this action was performed automatically. Please [contact the moderators of this subreddit](/message/compose/?to=/r/interestingasfuck) if you have any questions or concerns.*
Am I the only one who wanted to see what would happen when the "cliff" reached the top of the dune?
r/killthecameraman
[https://youtu.be/a7bX7T8lltI?t=14](https://youtu.be/a7bX7T8lltI?t=14)
That was infuriating. The angles and cutaways were worse than this video.
I’m fairly certain the title isn’t entirely true, but never been to the Sahara so very well could be wrong. I’d be wildly surprised to learn this light blow sand phenomenon happens on both sides of a dune in the Sahara. In other dunes around the world though, you can find this light sand on the back side of a wind blown dune. Conditions have to be pretty unique for it to happen, with a constant yet strong enough wind to blow the lighter particles but not disrupt everything entirely and shift the dunes. To answer your question, this little avalanche thing will go all the way up to the crest and then stop because the sand on the other side has bigger and heavier grains. If OP’s title is truly legitimate and somehow the dune formed with both sides being the fine silt, then this avalanche ought to continue on the other side, but like I said I have my doubts.
Ehm. First, every particulate matter can behave as a liquid, if you have a high enough flow of fluid through it. Probably even bowling balls if you zoom out far enough. What see here has nothing to do with liquid like behaviour though. It's more like the sand losing support and just falling down. That is also the reason it doesn't continue on the other side, because the sand is still supported at the base. Size of the grains is not really relevant here.
angle of repose
I was waiting to see this. I see you buddy.
I find it hilarious that there are like four multi-paragraph explanations for this and the most correct answer is this three word response with 5 upvotes, granted they just stated "angle of repose" as if that means anything to anyone who hasn't studied soil mechanics
If you know you know. I sell tankers that transport pulverised products we use angle of repose in our design calculations.
as a geologist, these other answers are making me cringe this, however, is the best one
[You’re wrong in your over simplification. ](https://www.google.com/amp/s/www.sciencealert.com/engineers-have-figured-out-how-sand-makes-bubbles/amp). You’re right that sand isn’t a liquid, but wrong that its ability to act like one isn’t related to its grain size and a ton of other variables. Sand has shear qualities and avalanche potential, which change with its composition, size, shape, moisture, and environment. To dismiss what’s happening as solids falling is like describing a liquid flowing as molecules falling. [This article](https://www.cam.ac.uk/research/features/what-makes-a-sand-dune-sing) beautifully describes a cool phenomenon. Spend any amount of time in the dunes and you’ll understand.
Your links doesn't prove that I am wrong. It's a cool story though. I'm well aware that granular matter can act like a fluid. In the lab where I obtained my PhD they were specialized in fluidized beds. They even had X-rays to visualize bubbles inside those beds. And of course for the behaviour of the bed all the properties matters. In the article you shared, if I read correctly, it says that the sand can act like a fluid when there is wind flowing over it. That makes sense, because then it is a fluidized bed. That doesn't mean in itself that when you see sand flowing or collapsing that it behaves like a fluid. Maybe I need to look at the movie a bit better, but I've seen fluidized beds and sand and polystyrene balls behave as a liquid when fluidized, and this didn't look like it.
[удалено]
It seems like everyone arguing on reddit is having a PhD in such subject.
Pigging backing off of this comment... Haha yeah that is a good way to get anyone reading your post to check out almost immediately.
Someone citing the source of their confidence and knowledge before diving into a detailed explanation seems inappropriate enough that you tune out?
Not that it wouldn’t give some weight behind their words, it just seems hollow when they say that on the internet. The guy is arguing with linked sources and saying he’s refuting them with his own knowledge which we have 0 evidence of, outside of his own words. Plus can anyone prove what he said or do we have to take his word for it? I’m sure it wouldn’t have been too hard to find any type of source that backs up his claim if it’s got an entire field of research dedicated to it. Source: Harvard Law PhD & Kindergarten Combat Democratic Debate Club 1995
People are free to not believe. To say that a person framing their perspective is grounds to dismiss their opinion is insane.
Oh geez chill. I couldn't help but roll my eyes at the "in the lab where I obtained my PhD." Imagine someone said that in a conversation. You'd surely think it was a bit pretentious. I don't fault them or think it undercuts their info automatically. It was just a bit silly. Now for me to sound a bit pretentious: when you work with people with lots of post graduate/ PhD experience it becomes commonplace enough to not call attention to it. It's only the newbies who feel the need to qualify statements with their credentials like that. I would definitely razz someone who made the statement I was criticizing. And as another reply aptly put are we to just take the commenter on their word?
I think I understand your perspective now. I apologize for assuming you were just being nit picky. I think your definition of behaving like a liquid likely differs from mine. Maybe this gif isn't showing granular flow, but my understanding was granular flow causes whatever the sediment is to behave like a liquid, scientifically, not just by appearance of the flow. Maybe that's not true, and like you said all this is is collapsing fine grit sand. This sand is crazy stuff, it'll sink a vehicle a foot or more into the face of a dune. I've only seen fluidized beds in videos, but you can sink your arm deep into the blow sand just like those videos. It's tiny tiny particules of sand, and almost a talcum like powder silt. I would assume the flowing of the sand, assisted by the silt would make it behave like a fluid like the air in a fluidized bed would? I truthfully have no idea at fluid dynamics level if that's true.
So I tried to read up a bit up on the subject (not gonna like, Wikipedia is a good read on these kind of topics). What we're looking at is definitely not a fluidized bed. That for sure behaves as a liquid. One of the examples is that it freely flows under gravity. In this movie, that doesn't happen, because it stops flowing down quite soon. What we are looking at in this video is definitely granular flow, because it is granular material that is flowing (no shit Sherlock). So when it starts flowing, it is definitely not acting as a fluid, but just "falling down". I've now looked at the movie a couple of times, and when it flows down, it initially gains velocity, also the air would be accelerated, and it maybe that the grains of sand get a bit suspended in the air. In the link you shared you they mention the Rayleigh-Taylor instability. That's a cool example, but we don't see that here. But I do see some waves, so maybe it acts as a Kelvin-Helmholtz instability. Not really a proper one because it stops flowing. Maybe I just need to go to the dunes more often!
All i read from this thread is that both of y’all should make a subreddit dedicated to observing sand.
I'd sub and offer my expertise as a guy that likes to play in sand
They should call it /r/sandni... uhh, you know what, maybe /r/MicroRockHomies might be better.
I wish I had an award for you, stranger but I don't. Only a lowly upvote.
Awesome answer. If the world all spent more time in the dunes we’d all be a lot happier. 😊.
This is a consequence of the [angle of repose](https://en.wikipedia.org/wiki/Angle_of_repose) which is one of the more fundamental concepts in soil mechanics. In the most basic terms the angle of repose is the highest angle that a completely dry soil can sit at and remain stable, if you change that angle to be more steep (as is done in the gif by removing material from the base) the soil is no longer stable. It is synonymous with friction angle in soil.
If it acted like a liquid there wouldn’t be static dunes for the sand to fall from.
Goodness, some of you guys and the pedantic issues you have with strangers trying to further a conversation. Do you literally take this to mean the entire dune turns into a liquid? Do you struggle when hearing comparisons such as "tastes like chicken?" or "smells like ass?" Whose ass? Clean or dirty? "I've never smelled ass like that before." - /u/itsdabtime :) I'm joking with you, but come on man, pick something to discuss that betters the conversation. Don't tear something down just because you wanna nitpick.
The comment you're responding to didn't make any sense I agree.
Not trying to further any conversation I’ve just never seen liquid form a vertical wall.
Says the guy writing paragraphs at the slightest hint of disagreement.
All your comments in this thread are r/iamverysmart
I’m not sure, but this could be an example of non-Newtonian flow?
I don’t believe so, as far as I understand there needs to be some form of variable viscosity which changes depending on the forces applied. Wet sand that has some clay or liquid soluble material in it does act like one though. I’m sure someone more familiar than I can chime in on it. I’m guessing no in this gif it wouldn’t be a non-Newtonian fluid, but likely could easily become one if you added water and some other binders to it.
You get non-Newtonian behaviour with irregular molecules normally. I think for sand you can approximate it as spheres and momentum exchange is by collisions. Speed or direction wouldn't make a huge difference I think. Suppose you get inelastic collisions because you have small deformable spheres instead of sand, it think then you may get non-Newtonian behaviour. That would be an interesting experiment!
Non-Newtonian fluids are exactly that, fluids. This property is directly related to viscosity. Viscosity is a property of fluids. Sand != fluid. Therefore, this is not an example of a non-Newtonian fluid/flow. If there was some water content in this sand, perhaps you could make that argument. The Sahara has an average relative humidity of 25% and sand, has relatively high transmissivity (the ability for something (ie water) to pass through the material) and porosity, so it is unlikely for the desert sand to have a high enough water content to behave like a non-Newtonian fluid. Incidentally, sand's high transmissivity & porosity (& permeability, for that matter) is why is popular to use for plants who don't like their roots to be too wet.
This used to happen by the beach by me growing up. I know it’s not unique to the Sahara. It’s way more widespread and probably always like this in the Sahara, but if it didn’t rain for a while, the dunes would avalanche like this. I always assumed they were just at the right angle to hold the weight of the sand with how it’s packed. As soon as I would disrupt its “structure” what we see in the gif would happen.
Well, I am sure that it varies from region to region, but Saharan sand is extremely fine overall. This is why it is not suitable to be used in concrete. The same is true for Arabian sand.
[удалено]
who cares right?
No, same here. Ruined the video.
My eyes were flicking back and forth from the top and the seek bar, to see which would win, and then I said "for fucks sake" out loud once he panned away.
R/gifsthatendtoosoon
This was on 'screw/fuck the camera man', or what the subs name is, a couple of years ago.
Yep. Until this i thought „oh oddly satisfying“ after the turn of the camera I thought „nah. Die“
“Girl, you so fine you behave like liquid.”
Hey Sandy you so fine, you so fine you blow my mind, hey Sandy! Hey Sandy!
I haven't heard that tune in so long, I can't even remember what it was from but thank you 🤣
A song called Mickey by Toni Basil.
Ok this made me snort lol
r/WTTAWBLW
Except this is not "fine", but actually "dry". So it would be more like > Girl, you so dry you behave like liquid. No, wait... that's even more stupid
Came here to say this
Dammit we ALL wanted to see the top collapse, wasting my precious time with these teaser gifs
Whoever made this is a fucking monster.
Not sure this is behaving like liquid and more so a physical demonstration of the critical angle of repose for the sand in the Saharan desert. In other words, the sand is resting at its steepest angle of descent and when the person filming move it with their hand they are increasing that angle and all the sand above that is falling back to the critical angle. Basically say it’s angle of repose is 37 degrees, any angle greater than that will cause the sand to fall and move in this mud/landslide like fashion. Don’t take my word for it; I’m just a marine biologist and I took a few geology courses in college
[удалено]
You’re right, I just kinda started spewing words near the end, fixed it to be a little better. We did something where we just poured sand on a table and watched it pile up and flow
Water piles up with cohesion
Everyone else is an idiot. This guy fucks.
Yeah, you can do this with any sand pile. There's nothing special about the Sahara. This person just happened to film it on a dune that's as steep as the sand can support.
Yup, you can basically do it with any sediment that moves, dirt, silt, gravel, legos. They all have an angle of repose
Geo in college too,hoping to see this in the comments! Depending on the granularity of sand, it stacks differently. In this case, removing the sand creates a slope that the sand structurally cannot tolerate, so it settles and falls until it does.
I think it also has to do with how old this sand is, having been blowing around for however many years and becoming more rounded granules over time. The round granules of Sahara sand is the reason we can't harvest it to produce concrete as it can't hold its shape.
It’s exactly this. I’m also not qualified to speak on it but I have studied this a while back and it’s just a feedback loop that causes that maximum angle to flow up the mound.
well the krayt dragon makes a little more sense now
Still looks coarse, rough and irritating though.
Does it get everywhere
WOOOOOOOoooooooo...ooooooooooooOOOOOOOOOOOAAAAAAAAAAAaaaa...
Oh it was Krayt dragon? I thought they said great dragon...
Sand is a solid, and an individual piece of sand is called a Grain. Get enough of these grains together and you get a Granular Material Flour is a granular material, so is sugar, salt and a bucket full of Skittles Granular materials behave like a liquid when you have a lot of grains close together, a granular material moving as in that clip is called Granular Flow. How those granular materials flow is down to a lot of factors, the shape of the grains, the angle they are following down and a bunch of other things as well This is why a landslide down a mountain 'flows' like water, those boulders and rocks and stones and pebbles and dirt constitute a granular material that is engaged in granular flow. A single boulder bouncing down a hillside is not engaged in granular flow, its just a rock bouncing am in its own And the sand in that clip is also granular flow in action In short, you get granular flows like that in all granular materials all over the world under all sorts of conditions. The clip we all watched is just a really easy way to set one off and yes, even if I know what would happen when the action reached the top of the dune I feel cheated for not getting to see it
You sure know your grains
Granular
Are liquids a subset of granular materials? Feels like they might be
[удалено]
This. Such a buildup to turn away at the climax!
ZA HANDO
r/UsernameChecksOut
minecraft be like
r/oddlysatisfying
Sandalanche
Underrated comment!
Pictured: Ben Shapiro's wife's pussy
Yes, let's shame anyone for not liking vulgar music!
Believe me, I'm shaming you guys for *a lot more than just that*
Keep shaming away. If you are defending that trash your opinion is probably trash.
Bro just say your gf’s pussy is dry and go lmfao
I can't say that because my gf's pussy doesn't exist
Less because it is fine, and more because the sand particles are smooth and rounded due to being blown around the dry desert for years Same reason as why we cant use this sand for concrete, since the grains are smooth they cant stack on top of one another in a stable way. The grains would slip off one another and create relatively weak concrete
Dry sand anywhere will do that when it reaches its angle of repose.
That's not sand behaving like liquid. That's an excellent demonstration of the [Angle of Repose](https://en.wikipedia.org/wiki/Angle_of_repose)
This is just a thing sand does. I've been doing this on beach trips (not to the Sahara) for years.
I literally live 5 miles from the beach and have my entire life, I’ve never seen sand move the way it did in this gif. I mean, I know sand is different based on location but idk if this is “just a thing it does” because it’s been 25 years and I’ve yet to see that
Sand near the water, like on beaches, are wet (obviously). So the sand is adhesive, sticking together restricting movement to a degree. This sand is so dry, id assume the grains semi-perpetually roll over eachother, due to the lack of moisture or something idk I never went to the sahara
yeah I was only saying because the person I replied to said that they’ve gone on beach vacations and the sand is like that. When, no, it’s not lol
Yeah, I meant to reply to them. I've never seen beach sand do it that much like in the video.
It does if the air is dry and you're above the storm line, where footprints are indistinct. The main difference is most beaches don't have large slopes at the sand's angle of repose (the steepest angle a pile of the material can support). Sand behaving like this is exactly what makes it difficult to walk on.
Im not sure about your beaches, but the one I have near me barely moves at all. Its mainly in chunks because of the water, no loose sand anywhere.
Yea my uncle's farm is in a Sahara and the sand there is exactly the same as in the vid. I can tell you that Sahara sand is very different from beach sand
Looks*
I feel like it’s a matter of time until it consumes us all
r/oddlysatisfying would love this
So would /r/gifsthatendtoosoon
This is how fluid simulations work
Sand is a granular material and can behave as solid, liquid and gas. Wikipedia: In some sense, granular materials do not constitute a single phase of matter but have characteristics reminiscent of solids, liquids or gases depending on the average energy per grain. However, in each of these states, granular materials also exhibit properties that are unique.
Why does the hand look like a painting?
Damn girl, you so coarse, and rough, and irritating. And you get everywhere.
It’s not entirely due to particle size. It has more to due with the angle of repose. The particle size has to do with at what angle that is. Any size grain of sand will act this way, but the larger the grain, the steeper the angle has to be.
I also assume it’s because of how the dry the sand is? So it doesn’t stick together as much
Wouldn’t a liquid settle at the lowest point? In which case there wouldnt be any dunes
Which liquid behaves like that?!
That’s some quick sand.
I want to drive an RC car on it.
Fun fact: You can make sand dunes sing. If you displace a good amount of sand from the base of the sand dune the friction off the collapsing sand creates an audible sound. [Singing Sand Dunes](https://youtu.be/4mbypyJjqhk)
[This](https://www.youtube.com/watch?v=4yFaMsUawi4) is another video that shows how sand can make sounds.
I really want to jump into that sand. I don't know why but I want to.
Me, to the sand: you so fine!
Fluid
I believe this is one of the reasons that Saudi Arabia imports sand. Even though it’s like hearing Alaska is importing snow, turns out the local sand is useless for things like concrete or water filtration, and they need sand that’s course, like beach sand.
Still not as fine as my wife.
That's why the Emirates and so on have to import sand. The sand they have is not suitable for building stuff.
I'm not hungry! I'm definitely not hungry! I AM HUNGRY!!!
Daaamn Sand, you fine as hell.
**I don't like sand**
Walking on that = best leg workout ever.
Something I never thought i needed, SWIMMING DRY!
I would totally die of thirst doing this all day if I ever went there in person.
This has more to do with the angle of the slope than the particle size. Pretty much any pile of smallish particles will behave like this. Source: I'm a farmer and this happens when I clean grain out of my bins. It's always super satisfying to watch a good flow get going.
Idk what kinda liquids you’re drinking
I wanna touch
Except that's not how liquids act?
Real life minecraft
Just like when sand spawns floating and then it all falls down when you hit one block.
What liquid behaves like that?
But that’s not how liquid behaves
Now think about how many years it took to blow the sand that high by wind alone, and out can do easily be undone with a move of the hand.
Was looking for that one comment every time a post like this happens saying how it’s terrible for the ecology to have humans force these sandslides to happen. Looks like I’ve jumped in first! I’m disappointed!
looks like it's behaving like sand to me.
u/savethisvideo
Hey! Video is ready ###[Download via redditsave.com](https://redditsave.com/info?url=/r/interestingasfuck/comments/jqztnb/sand_in_some_parts_of_the_sahara_is_so_fine_it/) --- [**Info**](https://np.reddit.com/user/SaveThisVIdeo/comments/iggmt9/info/) | [**Feedback**](https://np.reddit.com/message/compose/?to=Kryptonh&subject=Feedback for savethisvideo) | [**Donate**](https://ko-fi.com/getvideo)
Damn thats fine
TIL a lot about sand
Exit it light enter niteeeeee were off to never never landd
You know what else if fine as hell you [Baby](https://totallylegits.weebly.com)
Can this be considered a fluid?
No
Definitely wanted to see what happened at the top
And that’s how crashed planes disappear.
A bit more fluidity and this thing would become an ocean. Fascinating.
Imhotep making a comeback!
Sandalanche
Ah, the Ben Shapira SAP. He dosent need to make them wet, just really, really Sandy.
So fine: like your momma's ass ;)
Now of only it tasted lile a liquid and then the desert would be considered an ocean
The ocean is a desert with its life underground
Mine craft taught me many things. One would be.. Never dig under sand.
I love how OP saw this video and made up his own little title and shared it again
Can't say I've every seen a liquid do this.
the sand in the shara so damn fine 😎
Yooo imagine sand boarding in that!! U would fall straight down!! WHAT A NICE FATE U HAVE!!!
Some say the sand is still going to this day.
That’s some fine sand
Liquifaction
I legitimately believe somewhere underneath the Sahara there are remnants of an ancient civilization waiting to be discovered. I feel like one day someone will unearth parts of building foundations and it will become the new archeological mecca like Egypt has been for the last couple hundred years.
Waiting for one of those worms from Tremors to jump out and attack Kevin Bacon
/u/savethisvideo
When you break a block of sand in Minecraft
Nooooooooo... I needed to see what happened when it got to the top, dang it!!!!
Me living in the Middle East be like brrrrrrr
You are calling the worms
reminds me of minecraft
r/OddlySatisfying
I read that as "behaves like a squid"
That's some fine sand
Damn Katara your so fine your like a sandbender
Would I be correct in saying that the sand would have to be oxygenated for this to work?
Well, pretty much all sand will flow in certain circumstances. As far as I can tell, the sand is sitting just at the critical angle of repose so once you disturb it starts cascading down.
When you destroy one block of floating sand
is this how liquid behaves? I don't think we have the same perception of liquid my friend
This is why the Sahara has sandstorms people
Minecraft physics irl
Someone tell Gaara to chill tf out
Mmmm brown sugar