together by the combination of heat
still contained in the deposit after it
has come to rest and the weight of
overlying material.
Well An opening bored into the
zone of saturation.
Wetted perimeter The total
distance in a linear cross-section of
a stream that is in contact with
water.
Wind gap An abandoned water
gap. These gorges typically result
from stream piracy.
Xenolith An inclusion of
unmelted country rock in an
igneous pluton.
Xerophyte A plant highly tolerant
of drought.
Yardang A streamlined,
wind-sculpted ridge having the
appearance of an inverted ship’ s hull
that is oriented parallel to the
prevailing wind.
Yazoo tributary A tributary
that flows parallel to the main
stream because a natural levee is
present.
Zone of accumulation The part
of a glacier characterized by snow
accumulation and ice formation.
The outer limit of this zone is the
snowline.
Zone of aeration See Unsaturated
zone.
Zone of fracture The upper
portion of a glacier consisting of
brittle ice.
Zone of saturation Zone where
all open spaces in sediment and rock
are completely filled with water.
GLOSSARY
544