Day 22: Speed and
Melt of the Glacier
Some folks get to
spend the night on a glacier during this program. Unfortunately, I'm
not one of them. Any chance I could get some plants to grow up there by
So, what's the
challenge this time? Mike B. and I are responsible for determining if the
glacier is advancing or retreating over the next couple of days. We are
also supposed to make portable warming devices.
In order to see results,
we set up the glacier movement equipment today. We'll work on concocting
portable warmth tomorrow.
how do you measure if a glacier is advancing or retreating?
Background: A glacier is a "river" of ice that moves downhill
because of gravity acting on the glacier's great mass. So we know
a glacier is always moving and it is moving downhill. Whether it is advancing
or retreating is another story. This has to do with the amount of melting
that occurs at the end of the glacier vs. the amount of ice that is pushed
down each day. If more melting occurs than ice moving down to replace
the melt, then the glacier "retreats", actually it shrinks
by melting. If more ice moves down the valley that is melted away at the
end, then the end of the glacier is pushed farther down the valley, so
the glacier is advancing.
In either case, the
glacier ice is always moving downward. We are in the temperate zone and
this glacier extends below the snowline, so glacial ice is always melting.
(Snow and ice melts below the snowline.)
What is going on now?
From walking up the glacial valley, we could see several indications that
the glacier was once much longer that it is today. First, we saw striations
in bedrock where large boulders, carried by the glacier, had scraped against
bedrock, making deep grooves. Rock is hard stuff. Rivers carve out rock,
they don't make scrape-marks, so we can be certain that at some
point in the past the glacier, carrying large boulders, scraped rock against
rock. Second, as we looked around the valley, tall, mature forests were
found up high, while younger forests were found lower down. The closer
to the valley bottom, the younger the trees. This indicates that the glacier
has recently covered the lower area and has only retreated recently, which
allowed the trees to germinate and grow. The fact that the youngest trees
are at the bottom and they get older as one looks higher on the cliff
faces, says to me that the glacier once filled the valley to very high
up and slowly melted. As the area became exposed, trees grew. The last
area to be exposed from the ice is at the bottom.
So we know that compared
to today the glacier was well advanced in the past, probably a couple
hundred years ago. Maybe even up to 500 years, based on the age of the
What are we measuring to get an idea of what is going on with the glacier
We are set up to take
two different kinds of measurements. To measure how much (in distance)
the glacier is advancing or retreating right now, we set up a "triangle-broomstick"
contraption. Basically, we mounted the base triangle on bedrock (something
that will not move) and then marked on the stick the distance to the current
edge of the glacier. Because we are using a stationary base, bedrock,
we will be able to tell if more ice is moving down the valley than is
melting (advancing). Or, if ice is melting faster than ice is moving down
from the glacier (retreating).
second setup allows us to visualize the ice melting at the end of the
glacier. No matter if the glacier is advancing or retreating, ice is always
melting. We stuck several skewer sticks into the ice (with a drill). We
put them 5 cm down into the ice and from 2 to 6 cm from the edge of the
glacier. This will allow us to see how much of the ice at the current
edge of the glacier melts, both from the edge and from above. I think
this has the potential of being really cool as well as complementing our
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