1) Canyons
2) Mesas, buttes, spires
3) Alluvial fans
4) Tafoni
5) Salt flats
1. Canyons
Ephemeral river= one that flows occasionally
Exogeneous river= permanent, originates in uplands outside of the arid environments.
Slot Canyons:
Location: Antelope Canyon
- Canyons from ephemeral rivers
- Made from one rock type
- Prone to flash floods as there is no vegetation
Key features:
- Narrower than it is tall
- Smooth sides
- Sinuous
- Uniform geology (Navajo sandstone)
Overland flow from where the local LP system breaks through the global HP system causing a flash flood. Due to limited interception and baked ground means there is a high amount of surface run-off. The overland flow picks up weathered material from wetting and drying, salt crystallisation, insolation/exfoliation, hydrolysis and freeze-thaw weathering. The weathered material abrades the sides of the canyon meaning there is a wider bottom than the sides.
Grand Canyon:
- Canyon formed with glaciation (relic landform)
- Stepped appearance
- Key processes: abrasion, hydraulic action
FACTS:
- Colorado river has had the same course for the last 6 million years.
- River at deepest= 1600m
2. Mesas, Buttes, Spires
Location: Monument Valley
DeChelly sandstone (least resistant)
Organ shale (average resistant)
Parallel retreat= Occurs because rock debris is removed as fast as it accumulates.
3. Alluvial Fan
Location: Panamint Range, Death Valley, California
Increased friction means a decrease in energy leading to the deposition of sediment dropping the largest particles first.
4. Tafoni
Location: Snake Valley, Crystal Peak, Utah
Facts:
- 300m high
- Inselberg=crudely stratified
- rock type= porous & permeable (petrified volcanic ash)
- contains CaCO3 (calcite)
Definition= large hollows found in rock faces in semi-arid environments commonly <4m wide. They are a product of weathering (salt crystallisation).
Process:
- Weakly acidic due to CO2 in the atmosphere is dissolved in the rainwater forming carbonic acidic.
- Carbonic acid dissolves the calcite (Carbonation)
- The evaporation of this leaves salt crystals of calcite in the pores of the rock.
- This causes the process of spalling leaving holes in the rock.
5. Salt Flats
Location: Bonneville Salt flats, Utah
Process:
- High rates of evaporation bring salts to the surface
- Surface run-off dissolves the salts running into the nearest lake or river
- High temperatures lead to evaporation of the lake
Facts:
- 1.8m deep
- 4 levels are sodium chloride, sodium sulphate, sodium carbonate and calcium sulphate.
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