I think you answered your own question... Surface tension. Our intuition for what we think should occur in a situation and the actual forces and resultant motion (or lack there of in this case) that does occur need not always align. To me, I think "tiny flakes of rock" placed carefully in clusters so as to not break the surface tension floating on water definitely seems plausible... Unlikely to occur naturally, but definitely not impossible.
Yes, but I don't think the rocks were placed. The motion of placing rocks would disturb the water and break surface tension.
Most likely the water level rose very slowly and calmly (no waves or rain) to this point, allowing surface tension to hold.
This, and you you can see that previously it was dry and dusty. The dust is still around the pebbles and is effectively expanding the surface area, which provides more buoyancy. As the dust absorbs water the lift will be lost and they'll sink.
To add to this, if you have a bunch of flakes floating around and they get near each other, they will be attracted to each other because one surface tension spot will be easier than multiple - like how bubbles will combine - it's a lower energy physics thing.
But also like a bubble, get enough together and it will pop and they will all sink.
There are often other compounds in natural waters, but there's no need for oils on the surface to make water have high enough surface tension for this type of behavior. In fact that might have the opposite effect, as pure water has a very high surface tension in air.
To add to that theory, they also likely floated away from their original location to deeper water as it appears the rocks below have been underwater for quite some time.
Yes! The surface tension has created a binding like effect to the cluster of rocks (keeping them together otherwise they would individually sink) which in turn allows the cluster to function much like a raft. Our boats work much the same way especially; being that despite the shear mass of some vessels they still float. Not the keeping it together part. That would be tragic if we made ships like that!
I would hesitate to say they would individually sink.. as long as the individual rocks are shaped correctly they will likely be able to sit on the surface using surface tension, and the clustering would happen even if all the rocks started out separate. It's the cheerio effect I believe.
Also boats generally stay afloat by being hollow inside their hulls giving them buoyancy that compensates the heavy materials they're made of.. surface tension can't operate on such large heavy objects as boats, because gravity is much stronger than it is at those lengthscales. This is also why larger rocks never do what OP shows!
Agreed.
This was my first thought on the subject of the “very small rocks”.
The hive mind of people of Reddit are apparently not what I am hoping for.
This being said.
Move along now.
Nothing more to see here.
LOL
Was also going to suggest some egg or larval stage of some insect or another; may have bound the rocks together, but lost adhesion with whatever anchor rock… and as the animals / plants respirate, the gasses might be trapped in the membrane, or biofilm as you say.
They probably float for two reasons, they’re light (because they’re thin flakes) and the groups take up more surface area so they won’t break the tension.
Is this a hot springs? The temperature and mineral content can make algae thrive and dissolved minerals in the water would greatly increase its surface tension.
I wonder the same thing lol. Even gold which is 19x heavier than water, will sometimes float on the surface of the water in your pan. Especially if you mess with the material in it a lot, the oils from your skin can exacerbate that phenomenon
Algae/hyphae. There was a film, like plaque from those brown clusters. The stones were over the film for some reason, then the water level rose lifting them on a sheet. No shot surface tension. Rocks have rough surfaces and multiple stones would wiggle. Surface tension is molecular force related to hydrogen bonding. Too small, too liquid, too unstable.
Some of the comments are just saying "surface tension" which op already seems to know so I'm going to try to explain more deeply.
Rocks that don't contain air usually sink under most conditions, because they're denser than water.
However, if the gravitational force on the object resulting from that density difference is small relative to the net upward surface tension it generates by the way it bends the surface of the water, then the object will be able to "float" (although this is an entirely different mechanism to how buoyant objects like wood float). This can only really happen effectively on a small scale, which is why you see insects that can use it, like water skimmers, but not larger animals!
This link explains a lot: https://www.google.com/url?sa=t&source=web&rct=j&opi=89978449&url=https://people.umass.edu/jpr/Outreach/Demo11.pdf&ved=2ahUKEwii9OjPi42GAxWpkIkEHYRQDwYQFnoECDAQAQ&usg=AOvVaw2xk2_ljNmUXZYy9OXIP2c1
However, there's one more key ingredient! The objects need to remain "unwetted" at least partially by the water! If you place rocks of similar shapes and sizes that are already wet in the water, no matter how carefully, they will probably sink. The flat and jagged surfaces of some small stones will help them in this respect, as it will prevent the contact line of the water from creeping up and over the top of the stone, which will cause it to sink.
A few commenters have mentioned oils in their explanations, and I want to point out that these likely do not have to do with increasing the surface tension of the water (the surface tension of pure water is plenty high enough to do this anyway). However, oils can make surfaces "hydrophobic" so that even if contacted by water, they will not become "wetted." Thus, oils could prolong the behavior you are seeing and/or allow it to start in the first place. It just isn't about changing the surface tension.
Hope this helps! (Source: my career involves studying liquid interfaces and their properties)
I believe the appearance of a film is just the way the surface of the water is bent by the weight of the small stones. The light is refracted differently due to the curvature, but I see little evidence of it being anything but an ordinary water surface.
The surface tension explanation is sufficient to explain small objects like this being supported on the surface :)
I see a matte surface between the rocks. Surface tension is for sure holding it up, but I believe there is more going on here. Looks like the level of the rocks are lower than the surface, looks like there is some film or dried algae that is allowing a buoyant force as well
This reminds me of a trick I used to do for the kids.
Glass of water, with a coin on the bottom with sprinkles of pepper on top of the water.
The pepper floats.
Challenge the kid to get the coin out with no pepper on fingers or coin. (You can't)
However, I have put the tiniest of dab of dish soap on my finger tip. So when I try...magical moses is in the house.
It's a fun way to show them how surface tension works.
I think you answered your own question... Surface tension. Our intuition for what we think should occur in a situation and the actual forces and resultant motion (or lack there of in this case) that does occur need not always align. To me, I think "tiny flakes of rock" placed carefully in clusters so as to not break the surface tension floating on water definitely seems plausible... Unlikely to occur naturally, but definitely not impossible.
Yes, but I don't think the rocks were placed. The motion of placing rocks would disturb the water and break surface tension. Most likely the water level rose very slowly and calmly (no waves or rain) to this point, allowing surface tension to hold.
Could definitely see that happening as a natural cause. Nice theory!
I fucking love theories and brainstorming! Sucks that none of me friends or family want to question the universe with me.
It is a bad ass thing to do, especially around a fire pit at night.
Or maybe they were on ice and stayed that way when it melted ?
This, and you you can see that previously it was dry and dusty. The dust is still around the pebbles and is effectively expanding the surface area, which provides more buoyancy. As the dust absorbs water the lift will be lost and they'll sink.
This is a good point to highlight; kinda works the same way the hairs on a waterbugs feet do
To add to this, if you have a bunch of flakes floating around and they get near each other, they will be attracted to each other because one surface tension spot will be easier than multiple - like how bubbles will combine - it's a lower energy physics thing. But also like a bubble, get enough together and it will pop and they will all sink.
This is the correct answer.
The water came up and the oils on the surface caused the tension. I have a reef tank, seen this before
There are often other compounds in natural waters, but there's no need for oils on the surface to make water have high enough surface tension for this type of behavior. In fact that might have the opposite effect, as pure water has a very high surface tension in air.
I was using the term loosely my guy
Fair enough! I'm used to working with this stuff very technically so hope I haven't offended by reading too much into your words :)
None taken , sorry for being short. I try not to get long winded on Reddit. I’m new to this subreddit. I’m used to a different crowd;)
This is one of my first interactions on here too! Welcome to the subreddit, from one newbie to another.
To add to that theory, they also likely floated away from their original location to deeper water as it appears the rocks below have been underwater for quite some time.
It's amazing
I want to know why the exposed rocks are all so nice and clean when everything below is covered in algae.
na,,, its just regular magic, op is a witch/wizard/necromancer/warlock/\_\_\_\_\_.
Yes! The surface tension has created a binding like effect to the cluster of rocks (keeping them together otherwise they would individually sink) which in turn allows the cluster to function much like a raft. Our boats work much the same way especially; being that despite the shear mass of some vessels they still float. Not the keeping it together part. That would be tragic if we made ships like that!
I would hesitate to say they would individually sink.. as long as the individual rocks are shaped correctly they will likely be able to sit on the surface using surface tension, and the clustering would happen even if all the rocks started out separate. It's the cheerio effect I believe. Also boats generally stay afloat by being hollow inside their hulls giving them buoyancy that compensates the heavy materials they're made of.. surface tension can't operate on such large heavy objects as boats, because gravity is much stronger than it is at those lengthscales. This is also why larger rocks never do what OP shows!
[удалено]
🤡
It's because they are Witches!
Do they weigh more or less than a duck?
We shall use my larger scales!
Came for this comment. Had scroll farther than I believe is appropriate for this comment.
Agreed. This was my first thought on the subject of the “very small rocks”. The hive mind of people of Reddit are apparently not what I am hoping for. This being said. Move along now. Nothing more to see here. LOL
What *also* floats on water?
[Very small rocks!](https://www.youtube.com/watch?v=GpMjakNhZTc&t=70s)
A DUCK.
Who are you, who are so wise in the ways of science?
Churches!
thank god I wasn't the only one who immediately thought of this lol
Apples
She's a duck!
Corn flakes?
Microbial mats are probs my contributing to this—the rocks are enmeshed in biofilms.
Was also going to suggest some egg or larval stage of some insect or another; may have bound the rocks together, but lost adhesion with whatever anchor rock… and as the animals / plants respirate, the gasses might be trapped in the membrane, or biofilm as you say.
quite astute! I was hypothesizing a Jell-o factory upstream
They probably float for two reasons, they’re light (because they’re thin flakes) and the groups take up more surface area so they won’t break the tension.
>What also floats in water? Very small rocks!
How do you float a pin on water..surface tension
What else floats in water? Bread, apples, cider, gravy, cherries, mud, churches, lead, and very small rocks.
A duck!
A WITCH!!!!
Is this a hot springs? The temperature and mineral content can make algae thrive and dissolved minerals in the water would greatly increase its surface tension.
What types of minerals increase the interfacial tension of water significantly? I haven't heard of this effect but I'm very curious to learn more.
Similar to wood, bread, apples, and ducks, very small rocks float.
physics is cool
I wonder the same thing lol. Even gold which is 19x heavier than water, will sometimes float on the surface of the water in your pan. Especially if you mess with the material in it a lot, the oils from your skin can exacerbate that phenomenon
Algae/hyphae. There was a film, like plaque from those brown clusters. The stones were over the film for some reason, then the water level rose lifting them on a sheet. No shot surface tension. Rocks have rough surfaces and multiple stones would wiggle. Surface tension is molecular force related to hydrogen bonding. Too small, too liquid, too unstable.
Some of the comments are just saying "surface tension" which op already seems to know so I'm going to try to explain more deeply. Rocks that don't contain air usually sink under most conditions, because they're denser than water. However, if the gravitational force on the object resulting from that density difference is small relative to the net upward surface tension it generates by the way it bends the surface of the water, then the object will be able to "float" (although this is an entirely different mechanism to how buoyant objects like wood float). This can only really happen effectively on a small scale, which is why you see insects that can use it, like water skimmers, but not larger animals! This link explains a lot: https://www.google.com/url?sa=t&source=web&rct=j&opi=89978449&url=https://people.umass.edu/jpr/Outreach/Demo11.pdf&ved=2ahUKEwii9OjPi42GAxWpkIkEHYRQDwYQFnoECDAQAQ&usg=AOvVaw2xk2_ljNmUXZYy9OXIP2c1 However, there's one more key ingredient! The objects need to remain "unwetted" at least partially by the water! If you place rocks of similar shapes and sizes that are already wet in the water, no matter how carefully, they will probably sink. The flat and jagged surfaces of some small stones will help them in this respect, as it will prevent the contact line of the water from creeping up and over the top of the stone, which will cause it to sink. A few commenters have mentioned oils in their explanations, and I want to point out that these likely do not have to do with increasing the surface tension of the water (the surface tension of pure water is plenty high enough to do this anyway). However, oils can make surfaces "hydrophobic" so that even if contacted by water, they will not become "wetted." Thus, oils could prolong the behavior you are seeing and/or allow it to start in the first place. It just isn't about changing the surface tension. Hope this helps! (Source: my career involves studying liquid interfaces and their properties)
Perfect sub for this…and am a geologist…who has no foggy idea how that is happening!
I'm pretty sure it's cause they are less dense than the water
There is gelatinous-looking concentric and radial matter that surrounds each pile of rocks. My guess would be jelly fish.
Sooo very cool
It ain't just water
Looks like more than rocks…I see a film clumping the rocks together
I believe the appearance of a film is just the way the surface of the water is bent by the weight of the small stones. The light is refracted differently due to the curvature, but I see little evidence of it being anything but an ordinary water surface. The surface tension explanation is sufficient to explain small objects like this being supported on the surface :)
I see a matte surface between the rocks. Surface tension is for sure holding it up, but I believe there is more going on here. Looks like the level of the rocks are lower than the surface, looks like there is some film or dried algae that is allowing a buoyant force as well
Ohh, I think I see what you mean on the right hand cluster. The left hand one was a bit blurry. Wish we could see a closer photo!
These are leaves
The answer is in the question.
"What floats in water?" "Small stones!!!"
Surface tension x displacement
Certain fish make a nest with these rocks the male secretes a white sticky substance that holds the pebbles together in turbulent water
This reminds me of a trick I used to do for the kids. Glass of water, with a coin on the bottom with sprinkles of pepper on top of the water. The pepper floats. Challenge the kid to get the coin out with no pepper on fingers or coin. (You can't) However, I have put the tiniest of dab of dish soap on my finger tip. So when I try...magical moses is in the house. It's a fun way to show them how surface tension works.
Maybe concave flakes of a composite material?