article_snippet.sent: Linear dunes have also been known to merge and form so-called 'Y-shaped compound dunes', and the formation of these patterns are caused by the wind and movement of sand.
article_snippet.sent: Linear dunes have also been known to merge and form so-called 'Y-shaped compound dunes', and the formation of these patterns are caused by the wind and movement of sand.
article_snippet.sent: As the wind moves and switches direction the wind causes the sand to move accordingly and create grooves and ridges in the sand. '
article_snippet.sent: Linear dunes in the Namib Naukluft National Park, Namibia are shown.
article_snippet.sent: Linear dunes in the Namib Naukluft National Park have also been known to merge and form so-called 'Y-shaped compound dunes', and patterns are caused by the wind and movement of sand .
article_snippet.sent: Barchans' are crescent-shaped sand dunes (top left) that form in regions where there is almost unidirectional wind.
article_snippet.sent: If windblown sand comes from one direction, a dune will be a crescent-shaped barchan but if winds switch direction seasonally
article_snippet.sent: While in the 'Formation of the complex linear dunes in the central Taklimakan sand sea,
article_snippet.sent: China' study, Chinese researcher Xunming Wang and Xunming Wang colleagues said that in the case of 'complex' linear dunes - that are a combination of two shapes - the theory of Barchan evolution may play a role. '
article_snippet.sent: Barchans' are crescent-shaped sand dunes that form in regions where there is almost unidirectional wind.
article_snippet.sent: The shapes depend on almost unidirectional wind’s direction, and if windblown sand comes from one direction, for example, a dune will be a crescent-shaped barchan but if winds switch direction seasonally - coming from the southwest for half the year and from the southeast for the other half, for instance - a dune will be linear.
article_snippet.sent: If wind direction is more varied, star-shaped dunes appear.
article_snippet.sent: Mr Wang said: 'Complex linear dune formation is shown to have five stages. '
article_snippet.sent: Analysis clearly shows that under the control of wind regime, sand supply and other factors, the simple linear dunes move sideways while they evolve. '
article_snippet.sent: The evolutionary processes of complex linear dunes in the region partly support the theory of ‘barchan evolution’ but do not support the ‘roll-vortex’ and ‘bimodal wind regime’ hypotheses.'
article_snippet.sent: The researchers continued that after the complex linear dunes develop,  local wind patterns and the amount of sand suggest it is possible for The researchers to maintain The researchers linear shape, rather than evolving into star shapes for example, even as wind direction changes.