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Extreme Environments

Terms in this set (51)

Zone of accumulation
glacial area where inputs exceed outputs
Zone of ablation
glacial area where outputs exceed inputs
Plucking
erosional process where glacial ice freezes on rock and then removes rock as the glacier moves
Abrasion
erosional process where material carried by a glacier (or river/wind) rub against and erode other rocks
Freeze-thaw
weathering process where water enters cracks, freezes and exerts pressure on rock, process repeats and rock if broken apart
Till
mixed or unsorted materials directly deposited by ice e.g. moraine
Eskers
long, winding ridges of layered sand and gravel. They are formed inside the ice, in tunnels where meltwater streams flow.
Moraine
mounds of poorly sorted till where rock debris has been dumped by melting ice or pushed by moving ice
Terminal moraine
till deposited at the end of an ice sheet or valley glacier
Medial moraine
till deposited where two glaciers meet
Lateral moraine
till deposited at the edge of a glacier at the valley side
Erratics
boulders carried by ice, often for many kilometres, and deposited in areas of a different rock type
Corrie / cirque
an armchair shaped hollow, high on a mountain with a steep back and side walls.
Pyramidal peaks
a sharp summit with steep slopes on at least three sides. They form where three or more corries erode back so far that they produce aretes
Arete
a narrow knife-edged ridge where two corries have eroded back to back.
U-shaped valley
have steep sides and a wide, flat floor and are usually straight and deep. They are formed as glaciers widen, deepen and straighten river valleys
Truncated spurs
river valley spurs which have been cut off by the glacier to leave steep cliffs
Ribbon or finger lake
a large, narrow lake occupying a u-shaped valley. It forms in a hollow when a glacier has more deeply eroded less resistant rock or it may fill up a valley behind a wall of moraine across the valley
Misfit river
a small river that flows through the flat, wide U-shaped floor. They did not erode the valley, as they formed in the valley after glaciation had carved out the U-shaped valley.
Hanging valley
characterised by waterfalls. This is a side valley that had a smaller glacier than the main valley and so was not eroded as deeply
Tarn
a small lake which is formed in a corrie after the glacier melts
Roche moutonnee
a mound of rock with a smooth up-valley side due to abrasion and polishing and a steep lee side due to plucking
Drumlin
oval hills which form in groups called swarms. The unsorted till appears moulded by ice to form a blunt end with a more streamlined, gentler lee slope.
Periglacial environment
an area of permafrost found in high latitudes or at the edges of glacial areas
Permafrost
ground which is permanently frozen
Active layer
the upper layer of permafrost which thaws during the warmer summer months
Talik
unfrozen ground in an area of permafrost
Solifluction lobes
form on slopes when the active layer slowly flows over the frozen permafrost. The process is made easier because the grass roots are only shallow
Ice-wedge polygons
periglacial features formed as water enters cracks formed in frozen ground and freezes to form ice wedges. The process repeats each year and the wedges become deeper. From above the wedges form geometric polygons.
Closed system pingos
periglacial hill formed by pressure from underground ice
Arid
a dry area with a shortage of rainfall and a rate of evaporation exceeding that of precipitation
Infertile
an unproductive area with a shortage of nutrients and minerals
Rainshadow effect
dry region found in the lee of a mountain range
Weathering
the breakdown of material in situ (without removal)
Erosion
the breakdown and removal of material
Salt crystallisation
weathering process where the growth of salt crystals weakens rock
Disintegration
weathering process where the repeated heating and cooling of rocks causes rocks to expand and contract. The rocks weaken and fall apart.
Deflation
erosional process where wind erodes sand to form hollows
Oasis
A depression (often caused by deflation) where the water table meets the surface
Flash flood
a very sudden and intense flood event occurring in an arid environment
Barchan dunes
Crescent shaped depositional features formed where wind speed is high and from a constant direction
Yardangs
Wind-eroded landforms in areas of vertical rock strata. Soft rock is removed to leave long ridges of rock
Zeugens
Wind-eroded landforms in areas of horizontal rock strata. Soft rock is removed to leave mushroom-shaped pedestal rocks.
Plateau
A very large flat area at a relatively high altitude formed by tectonic uplift
Mesa
A large, isolated, flat-topped hill with steep sides separated from the main plateau. Top is wider than the base.
Butte
A small, isolated flat-topped hill with steep sides separated from the main plateau. Top is narrower than the base (Really a small mesa).
Pediment
A gentle slope at the base of a cliff formed from weathered cliff material
Canyon
A deep, steep-sided river valley usually filled with an exotic river
Wadi / arroyo
A dry valley eroded by flash floods and often filled by unrounded sediment
Alluvial fan
A cone of deposited sediment at the end of a mountain valley. Formed where the river enters a wider valley and loses energy because of increased friction and infiltration
Salt pan / playa
A depression filled with salt deposits from evaporated lakes
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