When wind-blown sand hits an obstacle, the sand can pile up into a mound or ridge called a dune.
(wind-blown sand; hits; an obstacle) (the sand; can pile up; into a mound; T:When wind-blown sand hits an obstacle) (ridge; called; a dune)
wind-blown sand the sand ridge
hits can pile up called
an obstacle
into a mound T:When wind-blown sand hits an obstacle
a dune