Introduction to Glaciers Flashcards
Glaciers cover how much of the planet?
10%
Arctic, Antarctic and Himilayas
An important source of…
Freshwater supply and water generation
Norway 98% of energy is from HEP- 15% of which comes from glacial catchments.
1 billion people live in the vicinity of the Himalayas- freshwater during the dry season.
The last ice age
Ended around 100 years ago
Covered around 30% of planet
Snowball earth
Entire earth covered in glaciers
Why are glaciers important in energy supply?
If the volume of ice changes so does the power distribution
Where do we find glaciers generally?
High latitude places
High elevation places
E.g Alps, Scandanavia
In order to have a glacier we need…
Snow on a mountain that’s going to survive summer.
Built up over years and snow will form ice.
Meltwater from the Himalayas flows into rivers that how many people rely on?
Over 1 billion people rely on for irrigation, livelihood,
power generation…
What basins are most susceptible to reductions of flow?
The Brahmaputra and Indus basins are most
susceptible to reductions of flow, threatening the food
security of an estimated 60 million people
Glacial hazards
As glaciers retreat…
…Moraines can dam meltwater creating a lake
If these lakes breach then can cause catastrophic floods
How to make a glacier?
Snow falling
As weight increases (compacted) = squeezing out air = ice crystals
What is a positive mass balance?
If a glacier is growing it has a positive mass balance
What is a negative mass balance?
If a glacier is shrinking then it has a negative mass
balance
What is the Equilibrium Line Altitude (ELA)?
Altitude on the glacier where the mass balance is zero is
called the Equilibrium Line Altitude (ELA)
What can be measured by field measurements?
Glacier hydrology
Glacier mass balance
Glacier meteorology
What can be measured by remote sensing?
Glacier surface
Glacier types
Cirque Glacier
– Formed in a cirque (bowl shaped depression)
– Significant accumulation from avalanching
Glacier types
Valley glacier
– Flow from the higher accumulation areas down to lower lying ablation areas
- Creator of fjords
Glacier types
Piedmont glacier
– Occur when steep valley glaciers spill into
relatively flat plains
Glacier types
Ice caps
– Defined either as a domed shaped mass of glacier
ice that does not completely cover the topography
– …OR < 50,000 km2
Glacier types
Ice sheets
– Defined either as a domed shaped mass of glacier
ice that completely covers the topography
– …OR > 50,000 km2
– Currently only Antarctica and Greenland, but paleo
examples exist
Glacier types
Crevasses
– reflect stresses imposed on the glacier by the valley sides
- water can melt its way down and ice can go all the way to the bed
Glacier types
Ogives
“Bands” on the glacier surface
– Light bands reflect the “clean” ice that passed over the ice fall in the winter
– Dark bands reflect the “dirty” ice that passed over the ice fall in the summer
What is clean ice?
Clean ice with almost nothing on it
What is debris ice?
If there are lots of monsoon action, avalanche, debris flows (material covering it).
Hard to tell ice is there.
What 3 ways can glaciers flow?
1) Creep (internal deformation)
2) Sliding
3) Deformation
Glacier flow
1) Creep (internal deformation)
Ice is a semi-viscous material and moves under its own weight.
This is when the ice is completely frozen, and the only way it will move is it will slowly deform.
Glacier flow
2) Sliding
Sliding on meltwater
If we have water on the bed, from either melt flowing down or volcanoes melting from beneath, this will cause the glacier to flow quicker.
Glacier flow
3) Deformation
The sediments deforming- if we have lots of soft sediments underlying these can deform (especially in water) and the ice can slide on these sediments.
What is geothermal heat?
Heat coming from the bottom of the ice.
How are glacial landforms made?
If heat is enough to melt the ice then we have water.
The ice slides on the water and carves the rock.
What is pressure melting point?
The temperature that ice freezes depends
on pressure:
– 0oC - atmospheric pressure
– Increases with pressure - 0.072oC per 106 pascals
What are cold-based Glaciers?
Entire glacier bed is below the pressure melting point
Entirely frozen
Only move by internal deformation (creep)
What are warm-based Glaciers?
Above the pressure melting point
Meltwater at the bed
Move by internal deformation, sediment deformation and basal sliding
What are polythermal Glaciers?
Areas where the ice is frozen higher up
Areas where ice is flowing on water lower down
What is supraglacial transport?
On top of the glacier surface
What two landforms does supraglacial transport create?
Lateral moraine
Medial moraine
What is a lateral moraine?
Parallel ridges of debris (from rock falls and debris slides)
deposited along the sides of a glacier
What is a medial moraine?
When two lateral moraines meet at a glacier confluence
What is englacial transport?
Where, in the summer, when there is a lot of water it will flow through the glacier.
Channels form.
What is subglacial transport?
Sediment being transported at the bottom of the ice.
What kinds of glacial erosion?
Abrasion
Plucking
Meltwater erosion
What is abrasion?
Sandpaper like erosion from rocks and stones engrained in the ice
Leaves behind polished surfaces with striations and rock flour
Factor of amount of/hardness of rock, pressure, velocity of glacier and presence of meltwater
What is plucking?
Dislodging and removal of rocks and boulders on the lee side of slopes
Leaves behind jagged landscapes
What is meltwater erosion?
Loosening, dissolving, and removing rock/debris
Water often at a very high pressure and carrying sediment
Large amounts of meltwater can increase sliding = further erosion
Scales of Glacial Erosion Landforms
Small – Striations, fractures
Medium– Roche montonee
Large– Cirques, troughs, arêtes and pyramidal
peaks
V shaped valleys are from…
Fluvial erosion
U shaped valleys are from…
Glacial erosion
