Extreme Environments Flashcards
Define sustainability
Social, economic, environmental uses of resources in a way that allows future generations to maintain their standard of living
Define arid and semi-arid
Arid: < 250mm rain per year
Semi-arid: 250mm-500mm rain per year
Define soil infertility
Lack of nutrients or bases in soils caused by low weathering rates, a lack of biomass
Insufficient nutrients to support arable farming
Define periglacial
Snow and ice cover on the fringe of glaciated areas, associated with permafrost frozen for 2+ years
High mountain and tundra areas of northern Eurasia and North America
Define permafrost
Permanently frozen subsurface (2+ years)
Define weathering and erosion
Weathering: breakdown of the earth’s surface in situ, without a moving force
Erosion: breakdown of earth’s surface by a moving force
Define desertification
The spread of desert or desert-like conditions
Define indigenous people
People native to an area who have been there for many generations
Define resource nationalism
Use of a country’s resources to benefit that country rather than allowing a TNC or another country to benefit
Where are cold and high-altitude environments found?
Cold environments: high latitude and high-altitude
Polar environments: North and South poles (low solar radiation)
Periglacial environments: belt in northern hemisphere (not much in southern)
Cold mountains: Himalayas, Andes, Rockies (temp down 10°c per 1000m up)
What four conditions determine the location of deserts and semi-arid environments?
1) stable, high-pressure conditions at tropics (Sahara, Australian deserts)
2) continentality- large distance from sea (Sahara, SW US)
3) rain-shadow effects (Patagonia, Gobi)
4) proximity to cold upwelling currents to limit air moisture
What are the conditions in cold and high-altitude environments?
Mountains: warm days, cold nights; lots of relief rain or no rain from rain shadow; hard to build / transport; overland run-off / erosion / thin soil
Polar: little rain
Periglacial: low evaporation → waterlogged soil; short growing season; can support people
What are the conditions in desert and semi-arid environments?
Desert: hard to farm without freshwater access; steep or flat; streams and flash floods
Semi-arid: possible to farm, especially with conservation methods
Warm, dry conditions good for tourism, especially near coasts
Why are there low population densities in extreme environments?
Extremes of climate: insufficient heat, insufficient water, etc
Fall outside of “comfort zones for human habitation”
Many areas are remote → costly communications, materials, imports
How do people cope in periglacial environments?
Periglacial pastures to herd / hunt caribou
Migration from tundra to forest margins
Fishing in rivers / oceans
Building on permafrost: raise buildings so nothing melts, thaw then build
Water supplies: nearby lakes / rivers, melting, protected pipes
Transport: constant repair to roads / bridges, dirt → gravel for drainage, paint roads white
How do people cope in arid environments?
Relief: travel on flat plains not slopes
Rainfall: lower rainfall → greater variety by year; sheet flow water instead of channels
Migration: rest in the middle of the day, avoid direct sun, long, loose-fitting clothes
Permanent water: settle near rivers
Remoteness: deserts can be remote from sheer size
How do glaciers grow and shrink?
Inputs: accumulation of snow, avalanches, debris, meltwater
Main store: ice; also carries debris, moraine, meltwater
Outputs: ablation (melting), sublimation of ice to water, sediment
Positive regime: accumulation > ablation (thicken and advance)
Negative regime: accumulation < ablation (thin and retreat)
Usually accumulation at high altitudes and ablation at snout
How do deserts’ distributions change?
Long-term changes in climate (more arid now than in rainy pluvials, same time as glacier advances)
Evidence from sand dunes suggest Sahara was wetter
Annual / decadal changes in rainfall → natural desertification
What are the methods of glacial erosion?
Plucking (base or side): meltwater seeps into rock cracks, freezes, rock ripped out of bedrock
Abrasion: debris leaves striations in rock, worn down to a rock floor
Other: meltwater, freeze-thaw weathering, pressure release
Fragments carried on top of ice (supraglacial moraine), under (subglacial), within (englacial)
How are cirques / corries formed?
Amphitheater shaped valley at glacier head
1) preglacial hollow enlarged by nivation (freeze-thaw and removal by snowmelt)
2) ice accumulates in hollow
3) at critical weight and depth, ice moves out rotating, eroding the floor
4) meltwater trickles down the bergschrund, cirque grows via freeze-thaw
After glaciation there’s a hollow and sometimes a lake
What other landforms are produced by glacial erosion?
Arêtes and pyramidal peaks / horns: headward recession of 2+ cirques
Glacial troughs: U-shaped valleys with steep sides and flat floors, truncated interlocking spurs of preglacial valley (shape / conditions depend on geomorphological activity)
Rock basins with ribbon lakes
Hanging valleys with waterfalls
Roche moutonnée: bare mound of rock smoothed by abrasion up-valley but plucked down-valley
What are drift and till?
Drift: all glacial and fluvioglacial deposits left after ice has melted
Till: glacial deposits, lodgement till by active glaciers and ablation till by stagnant or retreating ice
Till characteristics: poor sorting and stratification, mix of rock types, most striated and angular, long axis oriented in flow direction, some compaction of deposits
What are characteristics of moraine?
Moraines: loose rocks weathered from valley side and carried by glaciers
Terminal moraine: crescent-shaped mound at glacier snout, up-valley / ice-contact slope is steeper
Lateral moraine: ridge on the edge of the glacier and valley
Medial moraine: merge of lateral moraine in the middle of a big glacier
What are the characteristics of drumlins?
Small oval mounds up to 1.5 km long and 100 m high
Result of friction between glacier and underlying geology → glacier drops load
What are characteristics of erratics?
Glacier-transported rock fragments that differ from local bedrock
Used to indicate the direction of glacial movement
What are the three types of periglacial regions?
Arctic continental, alpine, Arctic maritime
Vary in temp → vary in frequency / intensity of periglacial processes