After noticing that the berm was consistently higher and thicker on one side of the table, despite the addition of sand to the "low" side, I finally broke out the spirit level. After leveling the table, I find the berm is now uniform throughout. Conclusion: the sand behaves like an extremely viscous fluid.
Maybe @Bruce knew this. Not me!
Interesting - though anecdotal, I didn't know that being level made much difference (within reason). I am, however, somewhat familiar the similarities - and dissimilarities - of particulate matter vs. liquid. They both flow and seek the lowest energy state when filling a volume, which tends toward a flat surface. But (and it's a big one) - particulate matter has non-zero angle of repose. For Sisyphus, the higher the angle the better (more shadowing). That's why glass beads don't work as well as silica. There are also all sorts of properties particulate matter displays that is not common in liquids - like static buildup, and bridging / clogging. Here's a project from WAY back that led to my fascination with particulate matter: Shimmibot.
Interesting. It would be moreso if the video links hadn't gone toes up! But the internet is forever:
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