Unlikeastreamwhichtransportssedimentindifferentpartsof

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Unformatted text preview: s
where
the
overlying
 weight
is
largest
 ‐on
the
surface,
ice
will
crack
if
there
is
enough
stress;
forming
crevasses
or
fissures
on
the
surface
 ‐deformation
deeper
in
the
ice
precludes
crevasses
from
propagating
downwards
greater
than
50m
 
 Basal
Sliding
 ‐ice
also
moves
by
sliding
at
the
bed
when
water
is
present
 ‐sub‐ice
volcanism
or
the
natural
temperature
of
a
glacier
may
allow
for
basal
melting
 ‐once
sliding
occurs
it
is
difficult
to
stop
because
the
friction
allows
for
more
melting
(feedback)
 ‐in
fast‐moving
glaciers
sliding
is
the
principal
way
that
motion
occurs
(~90%)
 Velocity
Patterns
 
 Q:
where
do
you
think
the
highest
ice
speed
is
in
a
valley
glacier?
 ‐in
the
center;
just
like
rivers
 ‐sides
experience
drag
along
the
valley
walls/bed
 
 
 
 Mass
Balance
 Q:
why
do
glaciers
grow
or
shrink?
 ‐because
they
lose
or
gain
mass
through
snowfall,
melt,
other
processes
 ‐this
is
called
mass
balance
 ‐mass
balance
changes
all
of
the
time,
daily,
seasonally,
yearly…and
on
longer
timescales
 ‐typically
mass
balance
is
measured
yearly
by
looking
at
the
amount
of
a...
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