Unit 3.3: Permafrost and Glaciers Flashcards
What is permafrost? What are some facts about it?
Frozen ground that remains frozen for more than 2 years.
- found between 15 cm and 5m below surface
- approximately 25% of the Northern Hemisphere consists of permafrost
- found in terrestrial and marine environments
What are the different types of permafrost?
- Continuous permafrost: area where more than 90% of ground is perennially frozen, found in high latitudes.
- Discontinuous permafrost: Between 50 and 90% of ground is perennially frozen.
- Sporadic permafrost: between 10 and 50 % is frozen.
- Isolated permafrost: less than 10% is frozen, found at the lowest latitudes.
What are the features of the permafrost soil column?
- Active layer: topmost layer that undergoes seasonal thawing. Melts and refreezes each year.
- Permafrost table: Marks boundary between 2 layers in a permafrost environment. Below this table, soil remains frozen year round.
- Talik: an unfrozen section of soil surrounded by permafrost.
What are some landforms that are common in a permafrost environment?
- Pingo: Hill with a core of ice. The sediment that surrounds it acts as an insulator. They are often small and in clusters. Occurs when water pushes through permafrost and pushes the earth up into a hill.
- Patterned ground: Surface of a permafrost environment that is arranged in a regular pattern of geometric shapes. Result of ice wedges that form due to seasonal freeze-thaw action.
- Drunken Forest: series of tree’s that have become tilted due to the melting of active layer. They are shallow rooted and can’t penetrate permafrost.
What is a glacier?
Thick, long-lasting, masses of ice that accumulate on land. Motion of ice is slow, a few cm to a m per day.
What is the only requirement for a glacier to form?
Snow input must exceed now output on a regular basis for at least 2 years.
Describe the formation process of a glacier.
As snow is added, it packs and thickens and squeezes. Then a firn forms, which is the recrystallization of snow. The firn then goes through additional compaction and recrystallization and turns into a glacier.
What are the two ways a glacier can move?
- Ice creep/Plastic deformation: Small scale movement, internal deformation of ice crystals slipping over one another as a result of the downward slope movement. Due to weight, slope, gravity, and partial melting of ice at depth.
- Basal sliding: Large scale movement of sections over the rocks below. Added seasonal thawing at base of glacier produces water at base, reduces friction, and allows it to slide.
What is the mass balance of a glacier?
Difference between input and output on a regular basis.
What zones is the mass balance different on a glacier?
- Zone of accumulation: area where summer melt does not exceed snowfall. New snow and firn is added yearly. This zone is found at higher sections of glacier.
- Zone of ablation: area where summer melt exceeds snowfall.
- Equilibrium line: boundary between the zones where input and output is equal.
What is the difference between glacial advance and glacial retreat?
Advance: when edge of glacier moves downslope
Retreat: when glacier’s toe moves up slope
What are the different types of alpine glaciers?
- Alpine glacier: form at high altitudes where snowfall is greater than snowmelt.
- Cirque glacier: Located in the headwaters within a mountainous region
- Valley glacier: flows and found in a valley
- Piedmont glacier: large, found in low lands or at the foot of a mountain.
What are the different types of ice sheets?
- Ice sheets: glaciers that form at high latitudes like Greenland. Typically greater than 50,000km^2
- Nunatak: isolated piece of rock projecting above surface of ice sheet.
- Outlet Glacier: stream of glacial ice draining parts of an ice sheet.
- Ice berg: large floating mass that has detached from ice sheet
- Ice shelf: flowing sheet of glacial ice, permanently fixed to land.
- Ice cap: essentially an ice sheet that is smaller than 50,000km^2
What are 2 different types of erosion to bedrock caused by glaciers?
- Abrasion: scraping of the bedrock caused by debris carried along the base of the flowing ice.
- Plucking: removal of large pieces of material that are frozen into the bottom of the glacier and transported by movement of ice.
What are 2 types of abrasion?
- Striation: Caused by rocks or other stuff in the glacier, they are scratches made by in the bedrock. Can be several meters long and centimetres deep. They provide an indication of which way the glacier was moving.
- Glacial polish: repeated scraping smooths the bedrock.
