Depositionalfeatures

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Unformatted text preview: dditions
to
the
ice
 (accumulation)
and
taking
away
the
mass
lost
(ablation)
 +
mass
balance
=
more
accum.
than
ablation;
‐
mass
balance
=
opposite
 ‐glaciers
tend
to
accumulate
in
their
upper
reaches
where
temperature
are
colder
(higher
up)
 (accumulation
zone)
 ‐they
then
melt
in
the
lower
regions
where
temps
are
warmer
(ablation
zone) ‐the
region
in
between
these
two
zones
is
called
the
Equilibrium
Line
or
ELA
(EL
Altitude)
–it
is
usually
 expressed
as
an
elevation
 
 
 ‐the
altitude
of
the
ELA
can
give
a
rough
measure
of
the
health
of
a
glacier
 ‐even
if
the
mass
balance
of
a
glacier
changes,
its
basic
shape
does
not
change
(other
than
getting
 larger/smaller)
its
slope
remains
the
same
 ‐this
is
because
ice
flows
like
a
conveyor
belt
from
the
accumulation
zone
to
the
ablation
zone
 ‐ice
lost
in
the
ablation
zone
is
replaced
by
ice
moving
downstream
from
the
accum.
zone.
 ‐when
we
say
a
glacier
is
retreating,
the
velocity
is
not
going
backwards
(uphill)
instead
it
means
that
the
 ablation
rate
exceeds
the
accumulation
rate
 
 glacier.jar
movie
 
 Q:
If
the
ELA
is
retreating
upglacier,
so
gaining
altitude
what
would
we
say
about
the
mass
balance?
 ‐losing
mass
 
...
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