So normally, wet sand usually is pretty solid, you can crumble it and other things, but when you shake it, it almost loses all its solid properties and flows. Why does this happen?
In: Geology
This is [what the atoms of a liquid do](https://en.wikipedia.org/wiki/Brownian_motion#/media/File:Brownianmotion5particles150frame.gif). That’s also kinda what the grains of sand do when you [blow air through the sand](https://www.youtube.com/watch?v=My4RA5I0FKs) or otherwise agitate.
Because when you shake it, the friction/movement is enough to jostle the structure of the block of sand. As many pieces break away from each other, the 1000’s of little breaks loosen the structure enough for them to break away from the faux solid you made.
Think of when you sieve flour through a strainer, pretty much the same thing.
Imagine, if you will, a box full of very heavy ping pong balls. The balls in the box have some sort of ‘structure’, they rest in each other in a stable position, and they aren’t constantly moving. This is dry sand.
Now imagine pouring water in to the box. It’ll flow between the cracks and perhaps change the structure a little, but fundamentally it can still be classified as a solid thing.
Now, if I tip the box, the balls begin to move. Normally,if there was no water, they’d settle relatively quickly. But because of the water, which flows but also acts as a lubricant, the balls find it harder to be stable and wind up “flowing”.
Replace ‘ping pong balls’ with ‘grains of sand’, and you have your simple explanation.
Latest Answers