UMMSAID   SAND RIPPLES

AMAZING  SAND RIPPLE  FORMATION

PROLICKING IN THE DUNES

MY  FOOTPRINTS  IN THE  SAND

MY  FOOTPRINTS

There are lots of fun facts about sand dunes. Did you know that?

• Sand dunes are classified by their shape. Crescentic, linear and star are the three basic dune forms. All other types of sand dunes are a subset of one of these.
• The strength and direction of the wind is one of the most important factors in determining the shape of a sand dune. But it isn't the only. Moisture, vegetation and landforms affect shape too.
• Sand dunes migrate and can move as much as 100 meters a year. The wind carries fine grains of sand and bounces heavier sand grains along. And while the wind isn't strong enough to move really heavy grains of sand, bouncing sand push the heaviest grains forward.
• Sand dunes have two faces. Sand builds up on a dune's windward face and slips down its leeward side, also known as the slipface.
• When a sand dune gets too steep it collapses under its own weight. A sand dune's angle of repose, the maximum slope before it starts to slide, is 34 degrees.
• Sand sheets and giant ripples are also formed by wind but they are not the same as sand dunes. Sand sheets, flats plains of sand, form when the grains are too heavy for wind to carry or bounce. Giant ripples, also called Zibars, don't have a crest they are rounded like the hump of a whale.
• Sand dunes exist on other planets too. There are sand dunes on Mars, Venus and Titan, Saturn's moon.