Glacial Processes Flashcards
What is a glacier?
A large mass of ice that forms over many years from the accumulation and compaction of snow.
Flows slowly downhill due to gravity, shaping the land and impacting the surrounding environment.
What is snow?
The material that hasn’t changed since falling
What is the density of snow?
50-200kg m-3
What is firn?
Wetted snow that has survived at least one melt season without turning to ice
What is the density of firn?
400-830kg m-3
What is glacier ice?
The interconnecting passes between grains that are sealed off
What is the density of glacial ice?
830-917kg m-3
When did the last glacial maximum occur?
20,000years ago before present
What is the last glacial maximum?
The most recent period during the earth’s history when ice sheets reached their maximum extent
What fraction of the earth’s surface is presently covered by glaciers?
1/10
How much of the Global North is covered by ice sheets/glaciers?
1.74m km2 (Greenland)
How much of Europe and Central America is covered by ice sheets/glaciers?
500,000km2
How much of the global south is covered by ice sheet/glaciers?
13.5m km2 (Antartica)
How much bigger was Antartica previously?
1.2 X
How much bigger was N.Europe Ice sheets?
1500 X
How much bigger was N.America?
1000 X
How much bigger was Greenland?
1.3 X
Why is it important to study glaciers?
To understand their decay and their role in climate and sea level change from past to future
What are the defining characteristics of a glacier?
- Ability to move
- Deform & Slide due to gravity
- Moves ice from high accumulation areas to lower ablation areas
What are the factors affected ice to snow?
Temperatures less that 0 mean that densification is due to compression and melting and refreezing - faster process
Temperatures more than 0 means that densification is due to compression from overlying weight of snow/firn
- slower process
How does a glacier move?
- Driving stresses pushes the ice down the slope
- Basal drag resists
- Ice then reacts like “hot” solids near melting point
- Deforming occurs due to this stress
What do early observations of glaciers show?
That flow wasn’t accepted until C.19th
What is iceberg calving?
A major component of ablation for tidewater glaciers
What happened in Greenland (Calving)
There was a widespread increase during 1996-2006
What did the increasing in calving coincide with?
A period of warming air temperatures
What is positive mass balance?
Accumulation > Ablation
Net GAIN mass = Thickening
(winter)
What does a bright white surface do?
Reflect large portions of SWR back
HIGH ALBEDO
Hinderance to melt
What does a dark dirty surface do?
Absorbs SWR
LOW ALBEDO
melts
What are three key processes of glaciers?
Crushing
Abrasion
Quarrying
