Wetlands, Peat, and Tundra Part 2
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What are the major landscape building features in northern systems?
glaciation and de-glaciation (above ground) permafrost and melting permafrost (below ground)
__% of earth’s surface used to be covered by ice sheets, today only __% is covered
30 11
Pleistocene glaciation was ___-___ yrs ago, and was the southern extent of the ice sheet in north america What were the 2 ice sheets associated with it?
1million to 18,000 yrs ago Laurentide Ice sheet- eastern North america Cordilleran ice sheet- western north america *between them= rockies
The _____ glaciation covered most of the northern half of north america 85,000-___yrs ago
Wisconsin glaciation 7000 = northern systems are still relatively young
Ice is heavy, so ___ the crust of the earth. When the ice melts, the earth __ resulting in lots of changes
compresses lifts
T/F The cypress hills were not glaciated by the laurentide ice sheet
true not glaciated at all= lots of species could survive
What are some of the consequences of the distribution of the proglacial drainage and the proglacial lakes?
• glacier melts= more water –> impacts fish etc • permitted fish etc to migrate northwards across present-day drainage divides • dispersal of some tree species into the deglaciated areas
Glaciation stripped away ___, deposited glacial ___, and created many ___ basins and ____
soil till/ drift lake riverbeds
Glaciers began to recede ~___years ago and forest cover gradually regenerated over Canada
20,000
The boreal forest took on its present character ~___yrs ago making it a ___ ecosystem
5000 young
What are 4 signs of glaciation left on the landscape (evidence)?
• glacial fluting • glacial moraines • raised beaches- isostatic rebound • eskers (water moves under the glacier, carrying sill)
Periglacial= ___of a glacier
edge
Permafrost=
earth material (soil, bedrock, clay, etc) that’s been below 0C for >2yrs, so it has become ice-cemented
Permsfrost can be ___-___ deep, with a much shallower ___ ___ that melts seasonally
200m-1km active layer
T/F 1. frozen land below glaciers is permafrost 2. Many trees are adapted to live in permafrost
• true • false - not many can live here; nowhere for the roots to go
Continuous vs discontinuous zone of permafrost:
Continuous zone= permafrost is found everywhere Discontinuous zone= permafrost is spatially sporadic
Mean annual air temp: - < -6.7C= permafrost is ____ - -3.9C to -6.7C= permafrost is ____ - -1.1C to -3.9C= permafrost is restricted to ___ - -1.1C= southern ___ of permafrost
continuous discontinuous peatlands (easier to have permafrost in peatlands b/c more insulated) limit
What is a talik? How does it form?
= unfrozen land surrounded by frozen land Happens b/c: - human modification - change in water flow - land below water = warmer b/c of water’s heat capacity - vegetation on surface is insulating
Give 3 reasons why peatlands are so prevalent in the north
• permafrost restricts movement of water • flat terrain can reduce water flow • short summers and cold temps reduce rates of decomp
3 conditions for peatland to form:
• annual precipitation must be greater than 500mm b/c soils need to become waterlogged • annual biotemp cannot be too warm • there must be a positive water balance in the area (sufficient water)
Melted water in permafrost areas can’t percolate through ice= ___ ___ develop and change ___ and the ___ below them
shallow lakes communities permafrost
cold soil temps found in some boreal forests result in: - reduced organic matter ____ - restricted nutrient ____
decomp cycling
Bogs have low____ and their only source of water is through _____. They’re pH is ____
nutrients (ie fertility) precipitation acidic
t/f bogs impact the water table
true