▁some ▁d unes ▁can ▁be ▁anch ored ▁in ▁place ▁by ▁veget ation ▁or ▁top ography , ▁prevent ing ▁their ▁movement . ▁ ▁Some ▁d unes ▁may ▁also ▁be ▁referred ▁to ▁as ▁stick y . ▁These ▁types ▁of ▁d unes ▁occur ▁when ▁individual ▁gra ins ▁of ▁sand ▁become ▁c ement ed ▁together . ▁ ▁St icky ▁d unes ▁tend ▁to ▁be ▁more ▁stable , ▁and ▁resist ant ▁to ▁wind ▁re working ▁than ▁loose ▁d unes . ▁B arch an , ▁and ▁Se if ▁d unes ▁are ▁among ▁the ▁most ▁common ▁of ▁desert ▁d unes . ▁B arch an ▁d unes ▁are ▁formed ▁as ▁wind s ▁continu ously ▁blow ▁in ▁the ▁same ▁direction , ▁and ▁are ▁character ized ▁by ▁a ▁cres cent - shape ▁at op ▁the ▁d une . ▁Se if ▁d unes ▁are ▁long ▁and ▁narrow , ▁featuring ▁a ▁sharp ▁cr est , ▁and ▁are ▁more ▁common ▁in ▁the ▁Sah ara ▁Des ert . ▁ ▁Analysis ▁of ▁ge ological ▁features ▁in ▁desert ▁environments ▁can ▁reve al ▁a ▁lot ▁about ▁the ▁ge olog ic ▁history ▁of ▁the ▁area . ▁Through ▁observation ▁and ▁identification ▁of ▁rock ▁depos its , ▁ge olog ists ▁are ▁able ▁to ▁interpret ▁the ▁order ▁of ▁events ▁that ▁occurred ▁during ▁desert ▁formation . ▁For ▁example , ▁research ▁conducted ▁on ▁the ▁surface ▁ge ology ▁of ▁the ▁Nam ib ▁Des ert ▁allowed ▁ge olog ists ▁to ▁interpret ▁ancient ▁movements ▁of ▁the ▁K uis eb ▁River ▁based ▁on ▁rock ▁ages ▁and ▁features ▁identified ▁in ▁the ▁area . ▁ ▁Organ ism ▁adaptation ▁ ▁Anim als ▁▁