Glacial Systems & Landscapes: Periglacial Processes & Landforms
- Created by: IssyCalderwood
- Created on: 01-04-19 13:00
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- Glacial systems & landscapes: Periglacial processes & Landforms
- Permafrost = permanently frozen ground w/ top layer that melts (active layer)
- 20-25% Earth's land
- Continuous = all ground frozen
- Mean annual temp = below -5 to form
- Discontinuous = patches are frozen
- Mean annual temp = below 0 to form
- Mass movement
- Temp above 0 = active layer melts but meltwater can't drain
- Active layer = waterlogged & heavy = flows easily
- Flow called solifluction, occurs wherever gradient
- Active layer = waterlogged & heavy = flows easily
- Solifluction lobe = when one bit of soil = faster than soil around it
- E.g. if its on steeper ground = flows further = tongue shape
- Can also occur through freeze thaw
- Soil = frozen = expands = soil forced upwards at right angles to slope
- Ground thaws = soil move vertically down
- As a result, soil ends up further down slope
- Ground thaws = soil move vertically down
- Soil = frozen = expands = soil forced upwards at right angles to slope
- Temp above 0 = active layer melts but meltwater can't drain
- Ice wedges formed by frost contraction
- 1.Temp drops = ground contracts = cracks
- 2. temp increase = active layer thaws = meltwater seeps into cracks
- 3. Permafrost's still frozen so water freezes
- 4. Re-open another year = splitting ice wedge more
- Patterned ground
- By frost heave or frost contraction
- Frost heave = water underneath stones freezes = force stone upwards
- Once forced up they roll down the mounds that have formed
- They form circles/polygons around them
- Once forced up they roll down the mounds that have formed
- Frost contractions = ground crack in polygon shapes = filled with stones = polygon patterns on surface
- Periglacial Landforms
- Pingos
- Conical hill = ice core
- Open system
- Discontinous permafrost
- Groundwater forced through gaps & collects together & freezes = core of ice = push ground upwards
- Closed system
- Continuous permafrost
- Forms when lake on surface
- Lake insulates ground beneath = remains unfrozen
- Lake dries up = permafrost advances around unfrozen ground = water collects in centre
- Eventually water freezes = ice core = push ground above upward
- Lake dries up = permafrost advances around unfrozen ground = water collects in centre
- Blockfields
- Expanses of loose rocks
- Formed in place by frost shattering of bedrock
- Terracettes
- Vegetation interrupts soil moving downwards (frost creep)
- Flat area builds up behind obstruction
- Thermokarst
- Ice in ground melts = ground collapse & holes form
- Become filled with water = uneven, marshy
- Ice in ground melts = ground collapse & holes form
- Pingos
- Permafrost = permanently frozen ground w/ top layer that melts (active layer)
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