Mountains are by far the oldest sand artworks existing:
if you see a mountain range you see primeval seabed, namely sand and silt transformed by pressure, heat or chemical reactions to solid rock, which because of the continental shift had been emerged from sea and folded up. Like a sand art they are succumbed to permanent movement, invisible for the human eye, because our lives are too short to see those changes.
Such a process takes hundreds of millions of years and would be subject of a breathtaking clip shown in a time lapse.
