however
the
quantities
of
each
form
of
water
-
liquid
,solid
,and
gas -
do
change
significantly
throughout
time.
during
the
last
ice
age
,over
thirty
percent
of
earth
was
blanketed
with
ice
.currently
,only
approximately
ten
percent
of
our
water
exists
in
the
form
of
ice