Flashcards in G - Glacial system Deck (19):
What are the inputs of a glacial system?
-Snow (from precipitation and avalanches)
-Condensation of water vapour from the air (which then freezes)
-Sublimation of water vapour directly to ice crystals
-Bits of rock collected when the glacier calves away the landscape and rocks that have fallen onto the glacier from above
What are the stores in a glacier system?
-Meltwater (it can be found on, in or below the ice
-Debris (rocks, gravel, sand)
What are the outputs in a glacier system?
-Ice can melt and flow out of the glacier as meltwater
-Surface snow can melt and evaporate
-Ice and snow can sublimate into water vapour
-Snow can be blown away by strong winds
-Calving (where block off ice fall from the front with glaciers that end at sea creating icebergs) (can also happen where there's a lake at the front of the glacier)
What is a glacial budget?
The balance between a glaciers inputs and outputs
What does the glacial budget show and determine?
It shows whether the volume of water in the glacial system has increased or decreased
It determines whether the front of the glacier advances forwards or retreats backwards
What is accumulation?
The input of snow and ice into the glacial system (most accumulation is snow)
What is ablation?
The output of water from a glacier
Where is there more accumulation in a glacier? What is this place called?
In the upper part of the glacier - this is called the zone of accumulation
Where is there more ablation? What is this place called?
You get more ablation that accumulation in the lower part of a glacier - it is called the zone of ablation
What is a glaciers equilibrium point?
The point where accumulation and ablation is equal
What happens to the glacier if there is more accumulation that ablation over a year?
It is said to have a positive regime (/positive mass balance)
- The glacier grows and advances (moves forward)
What happens to the glacier if there is more ablation than accumulation over a year?
It is said to have a negative regime (/negative mass balance)
-The glacier shrinks and retreats (moves back)
How does the glacial budget change throughout the year?
There is more ablation during the warmer months and there's more accumulation during the colder months
-Over the year these might balance out - meaning the glacier advances in the winter and retreats in the summer - so the overall volume stays the same
How can the glacial budget change over time?
Changes in global temperature over long periods of time can effect the glacial budget
eg temperatures in the 19th century were colder than the 18th century, so generally there was more accumulation than ablation (that means many glaciers advances because they had a positive regime)
Explain how glaciers are formed
- Snow settles (it has a loose, snowflakey consistency)
- The weight of more snow falling on top turns the snow into a denser, more granular kind of snow called firn
- Air is squeezed out, and particles of ice are compressed together by the continuing accumulation of snow and ice
- Water also melts and refreezes in the air spaces, making the ice more dense
How can glaciers be classified?
According to the temperature of their base
Explain warm-based (temperate) glaciers
In these glaciers the base is warmer than the melting point of ice - due to the
heat from friction caused by the glacier moving/because of geothermal heat from the Earth
Explain cold-based (polar) glaciers
The base is cold (usually well below melting point) so there is little melting and there is little movement as ice is frozen to the base of the valley
There is hardly any melting at the surface even in summer