The Tip
of the Iceberg on Glaciers
(Image Courtesy of the
Glaciers, Ice Caps and
Icebergs Website, 2004.)
Glaciers can be a combination of
ice, water, and
rock debris or sediment (
Rice University Website,
2004).
It may be
difficult to visualize, but these giant masses actually do flow with
gravity
due to their own heavy weight.
They are
by no means fast movers, but they can move ten feet or thousands of
feet
per
year.
Glaciers can be as large as a
continent or only take up a small amount of space. For example,
the valley
between two
mountains (
Rice University Website, 2004). As
they move,
they shape the landscape.
Let’s get a little
glacier lingo down cold first.
Accumulation refers to
the mass of snow added onto the glacier (World
Wildlife Fund (WWF) website, 2004). Therefore,
an accumulation zone is the area where mass is
added and none is lost (commonly the top of the glacier) (Rice University Website, 2004).
Ablation, on the other hand, is the
removal of mass from the glacier by means of melting, evaporation, or
calving (WWF website, 2004).
Calving, by the way, is the
breaking off of pieces of the main glacier.
You guessed it; the ablation zone is then, the area of
the
glacier where there is a loss of mass (Rice
University Website, 2004).
Two other terms you should know are equilibrium line and glacier
terminus. The equilibrium line is the actual physical spot on
the glacier
where the ablation zone and accumulation zone meet (Rice
University website, 2004).
No mass is lost or gained here. The glacier terminus is a fancy
way to say the leading
edge of
the glacier (Rice University website, 2004). So:
ACCUMULATION > ABLATION = Increase in Glacier Mass
ABLATION > ACCUMULATION = Decrease in Glacier Mass
ACCUMULATION= ABLATION = No Change in Glacier Mass.
So…Can
I just fill up my ice tray with snow and make my
own glacier?
Glaciers do not magically appear one
day and stick
around for no reason.
Precipitation and
temperature are key factors.
Precipitation is needed in the form of snow; and the temperature
needs to
be cold enough so that more ice accumulates than is lost (
WWF website, 2004).
Forming a glacier is not as simple as
freezing snow.
While snow is a
necessary ingredient, it is not solely sufficient.
Precipitation in the form of snow falls on
the glacier.
As more snow falls on top
of it, the lower layers get compacted from the weight of the more
freshly
fallen snow.
This compacted snow
becomes one with the glacier (
Rice University
website, 2004).
This
process does not happen overnight, in fact, in the South Pole, it takes
about
1,000 years for the snow to turn to glacial ice (
Rice
University website, 2004).
Where are glaciers located, and are
there different kinds? Click next to find out!