Most ventifacts in the northern U.S. formed during the Pleistocene when vegetation was sparse and wind-blown sand and silt was abundant.
(Most ventifacts in the northern U.S.; formed; T:during the Pleistocene; T:when vegetation was sparse and wind-blown sand and silt was abundant) (vegetation; was; sparse and wind-blown) (sand and silt; was; abundant)
Most ventifacts in the northern U.S. vegetation sand and silt
formed was was
T:during the Pleistocene T:when vegetation was sparse and wind-blown sand and silt was abundant
sparse and wind-blown
abundant