Why are some places are considered to be extreme environments? (The…
Why are some places are considered to be extreme environments?
The distribution of extreme environments
Cold and high altitude environments
Generally, high latitudes and high altitudes
Located towards the N and S Pole where insolation is low; Arctic and Antarctic circle 66’ 34’’N and S
Insolation low due to:
Earth's tilt and spherical nature: curvature creates more surface to be warmed and more atmosphere for SW radiation to pass (more chance for reflection and absorption)
Seasonality > winter daylight can be minimal > net heat loss
Associated with higher altitudes: Himalayas, Andes, Rockies
Air temp decreases by 10’C every 1000m (1'C every 150m) > decreasing air pressure > atmospheric molecules gas spread, dispersing temperature and cooling easily.
Tundra/periglacial - located at the edge of polar regions; presence of permafrost - persistent sub-surface soil freezing for 2 years)
Located in Northern hemisphere, (a belt of periglacial environments) straddling the Arctic Circle (latitude: approx 67' N).
Lack of presence in south > lack of land mass at this latitude 60-65’ S
Hot desert (arid) and semi-arid areas
Cover as much as a ⅓ of Earth’s land surface.
Central and western Australia, Sahel region of Africa, Namibia (Tropic of Capricorn), continental China, central and western USA, Central America, Chile - straddling the Andes and Pacific cold ocean current.
Generally, located around tropics (23.5') > permanent high pressure systems (descending air) limiting (rising air) and rainfall.
Four factors explaining the location of the world’s main deserts:
High pressure persistence
Continentality - distance from a major water source
Rain shadow effect
Proximity to upwelling cold currents - limit the amount of moisture available in the air.
The conditions of extreme environments
relief, climatic characteristics, rainfall unreliability, intensity and flash floods
Precipitation - effectively cold deserts - lack of precip. due to low evaporation, zones of descending air.
High altitude environs can be characterised by warmer days and very cold nights
Can receive high intensity rainfall due to altitude and relief precipitation; conversely, low precipitation due to being on the leeward side of the rainshadow effect.
Links to monsoonal Nepalese mass movements
Relief > steep = difficulty to build on; transport barriers.
Thin, skeletal soils - weathered rock moved downhill by gravity; high rates of overland runoff and erosion.
Low temps, low evaporation, low rainfall
Frequently waterlogged soils
Short growing seasons with temps above 6'C for only a few months each year.
Prudhoe Bay, Alaska climate: AVG high temperatures: -20'C - -24'C (Dec-Feb), 4 months above 0'C (Jun-Sept) 3-12'C; Annual precipitation: 102mm - highest in summer months (August: 24mm)
Hot desert and semi-arid areas
Niger climate: AVG daily temps seasonally range from 20-35'C; on average 44mm of annual precipitation (summer/monsoonal?), highest in July/August
Aridity a constraint for development: human use and agriculture
Relief can be challenging - ancient landscapes eroded by water over time into canyons, etc.
Subject to intermittent high intensity rainfall due to strong convection > in the presence of moist > strong convection > air rises and cools rapidly, condenses, forming cumulonimbus storm clouds
In response, subject to flash flooding: raindrop impact compacts soils, reducing infiltration > precipitation exceeds infiltration > runoff > flash flooding
C.1 Concept mapping