History shows no record of King Ozymandias. And yet his name is famous because of a short poem by Percy Shelley which evokes the futility of human grandeur and the inevitability of ultimate triumph by the elements - in this case by the desert sands: I met a traveller from an antique land
Who said: Two vast and trunkless legs of stone
Stand in the desert.
And on the pedestal these words appear:
My name is Ozymandias, king of kings:
Look on my works, ye Mighty, and despair!
The desert always moves. The wind picks up the tiny grains of sand and transports them for some distance until they fall to ground again by force of gravity. Where there are obstacles, like Ozymandias's ruined palace, in the way, the grains are trapped behind them, and gradually the sand accumulates until the obstacle is covered, and the way for onward movement is clear once more.
If the wind prevails for long enough from one direction, the sand accumulates to form a dune. The dunes themselves often migrate under the influence of the wind, engulfing deserted towns and the ruins of civilisations long since past. Thus the desert wind can sculpt the landscape, producing many strange unusual shapes, some of them majestic, some grotesque. And on a smaller scale, the sand moves around on the surface of the dune itself to produce wavelike patterns, or ripples, perpendicular to the wind's direction.
The ripples occur because an area of loose sand is never entirely smooth. Here and there, inevitably, will be indentations of some kind, one of which, for the purposes of this exercise, we will imagine as a little valley at right angles to the wind. Airborne grains tending to fall in this vicinity do not land on the upwind side of this valley, but rain down on the opposite face; in so doing they tend to push up the slope those grains already there, creating a small hill on the downwind lip of the existing trough.
But the wind still blows. Sand grains on the newly created hill are plucked from the crest, and being broadly uniform in size and weight, are deposited a common distance downwind, thereby creating yet another little ridge. And so it goes; as the process continues, a state of equilibrium is reached for a given sweep of wind, whereby a series of ripples or ribs will have been created a cross the entire surface of the dune. Nothing beside remains.
Round the decay
Of that colossal wreck,
boundless and bare
The lone and level sands
stretch far away.