A
scientist
can
tell
____________________
fast
a
glacier
can
slide
.
A
rock
or
stone
on
the
glacier
will
slide
past
a
stake
in
the
sand
.
Scientists
will
use
a
clock
to
tell
how
fast
the
ice
slides
past
.
____________________
can
track
the
____________________
of
time
it
takes
the
glacier
to
pass
the
stake
.
They
can
tell
us
____________________
the
glacier
will
get
to
the
sea
and
melt
.
