Glaciers, Glaciation & Permafrost Flashcards
How does glacial ice form – on Earth? On Mars?
On Earth- Snow accumulates, compacts, melts and
refreezes - changes into firn; firn melts, compacts, and refreezes further and transforms into ice. Ice needs time to form. The forst step is glacier ice
On Mars- Ice is not just composed of water. It is completely different to ice on earth. It depends on the tilt of the axis
Where have glaciers been identified on Mars?
At the poles
How does glacial ice move? What factors affect rates of glacier movement?
- Gravity makes ice move
- Ice moves in responce to stress
- Movement or deformation of ice is called strain
- Ice moves the fastest in the center at the top
- friction of sides and bottom slow down movement there which is why the midle and top are faster
- not constant in velocity or speed
Types of movement: basal sliding, internal deformation, crevassing
What is a glacier budget?
- relationship between gain and loss of mass
- If more mass GAINED: positive buget and glacier terminus will advance
- if more mass LOST: negative budget and glacier terminus will retreat
- Mass gained in the accumulation area. zone of accumulation is usually up slope, new mass gained
- Mass lost in the ablation (wastage) area. Lost ice goes right to evaportation (skips melting)
How do we classify glaciers? What communities/regions are most impacted by
rapid glacier retreat?**
- continetal ice sheet
- ice cap
- outlet glacier
- valley glacier
- pidemont glacier
- cirque glacier
- ice shelf
- communties on the ocean front are most impacted by glacier retreat because rising water levels. andes impacted
What processes are involved in glacial erosion and glacial deposition?
- abrasion: debris in ice dragged across substrate; form striations (scratches), smooths the rock. Smoothed and streamlined landforms are formed for example, roche mountonee, whaleback. abrasion creates shapes stones (faceting) which are bullet-shaped boulders with a pointed end and a blunt end; this reduced grain sixe and produces silt
- occurs on bedrock, not made of sediment
- glacier erosion occurs at the base. Clean ice does not erode, it needs and abrasive device
- erosion by plucking which is debris released by fracturing of bedrock; frozen into glacer bed
- water seeps into cracks, freezes, and, mechanically breaks up the bedrocks. These fragements are plucked out by the glacier. Pressure causes change in melting point
What features of a landscape indicate cold climate conditions?
- glacier landforms (U-shaped valleys, cirqures, moraines)
- permafrost
- tundra ecosystem (low-lying vegatation, polygons)
- Alpine Glacial Features (horns, arrets, cirque lakes)
Firn
snow which has survived a summer melt season and has begun to change into ice
basal sliding
- requires water at ice base
- need ‘warm’ ice
- e.g. Alaska, Rockies
internal deformation
ice deforms as a plastic material
crevassing
- upper surface of ice is brittle
- fractures, or crevasses form to allow movement
how quickly does glacier ice move
3 to 300m/year
where are the fastest glaciers found
- Alaska, Rockies
- ‘warm’ glaciers where ice is close to 0C
where are the slowest glaciers found?
- Antarctica
- Cold Ice
Ogives
- dirt bands in ice
- show differential movemen
ablation
dirty ice, old, downslope
equilibrium line (snow line)
- Point on the glacier where there is neither gain or loss of mass
- will move for places with seasion, ex. closer to ablation in summer
what determines how quickly ice moves?
- slope of glacier
- ice thickness
- Temperature
- Valley geometry
- Bedrock conditions
- Subglacial hydrology
how does ice flow?
- ice flows from accumulation area to abaltion area
- never flows “backwards”
-ex. south casacde glacier washington- ice front has retreated due to increased melt, it has not flowed backwards
contiental ice sheet
- bigger than 50000km^2
- Antarctica
- greenland,
- lauerntie ice sheet (used to be on top of hamilton 1200-1400 years ago)
ice caps
- smaller than ice sheets (less than 50000 km^2)
- often in mountainous areas
- ex. vatnajokull, iceland, southern patagonian ice field.
- Martian ice caps fall under this
outlet glacier
- radiate from the edge of an ice cap
- ex. breiamerkurjokull, iceland
- there are lots around the world
valley glacier
- flow in bedrock valleys
- ex. athabasca glacier (this one is melting which is alarming)
pidemont glacier
- valley glaciers that extend out onto lowlands
- ex. malaspina glacier, alaska
cirquce glaciers
- occupy small, semi-circular hollows in mountainous reigions
- ex, rockies, alps
ice shelf
- floating part of ice sheet or ice cap
- ex. ross ice shelf, antarctica
- they are evicence that we can see melting
ice field glacier
- relatively flat expanse of glacial ice that covers a mountainous area, often feeding multiple glaciers
tidewater glacier
- an outlet glacier that flows into the ocean
rochee mountee
- A glacially eroded asymmetric hill that becomes
elongate in the direction of flow; glacial rasping smooths the upstream part of the hill into a gentle slope, while glacial plucking erodes the downstream edge into a steep slope
whaleback
A streamlined rock knob with symmetrical longitudinal profiles caused by abrasion of both stoss and lee sides
