Day 22: Speed and
Melt of Glacier
Fresh snow falls and falls upon high,
On an ice mountain nestled in the sky.
Funnelled in between these high peaks,
On a slow journey downward it seeks.
Compacting, slipping in its mountain vice,
Five miles of hard sculptured ice.
Its vast slow weight compressing it hard,
Below ancient rock is cut and scarred.
A vast blue eternal ice train,
Shunting forward to the glacier moraine.
The day starts with
Kathy explaining to camera the maths of how you might determine the rate
at which the glacier is moving. We will use something called a plane table
survey to estimate the speed of the glacier. We need to measure angles
from two fixed points to a third point of the glacier - the two fixed
points being a known distance (baseline) apart.
start on a protractor good enough to measure the small angles that we
expect for the relatively small movement we will measure (given that we
only have one day). I decide to make up a protractor having a circumference
(180 degrees) of 180 cm so that each cm is 1 degree. 1/10 of a degree
is simply a mm on this scale and easily read off. Made up two of these
and painted the dials and made an angle arm so that angles can be measured
idea is that a flag will be fixed in place at a prominent place on the
glacier ice. This will be visible at each of the sites of the two protractors
which will be set up on land. These protectors are 50 m apart and visible
from each other. By measuring the angles we can work out how far the flag
is away. If we do the same measurements the next day we will have two
positions for the flag corresponding to the movement of the flag from
one measurement to the next. From this we can determine the amount of
movement over one day and therefore the speed of the moving glacier.
Kathy, Mike and I
make up the protractors, tripods and flags for the measurement. We do
a dry run on land and this works out very well. So we know the equipment
and ideas are working OK, this is a great way to end day 1 - very happy.