Chapter 2 - Hot Deserts systems and landscapes Flashcards
What is an arid environment?
- The Climate of an area that receives less than 250 mm of precipitation per year.
What is the aridity index?
- The ratio between precipitation (P) and potential evapotranspiration (PET).
What is continentality?
- The impact of increasing distance form the coast on the climate of an area.
What is a desert?
- An arid environment receiving very low levels of rainfall.
What is a semi-arid environment?
- The climate of an area that receives between 250 and 500 mm of precipitation per year.
What is the water balance?
- The relationship between the annual precipitation received and the amount of water lost to potential evapotranspiration.
What is an abrasion?
- Where material carried by moving wind of water hits exposed rock surfaces, thus wearing the away. Known as the sandblasting effect or sandpaper effect.
What is chemical weathering?
- The processes leading to the decomposition or breaking down of rocks due to chemical reactions. This most often requires the presence of water, and /or exposure to the air.
What is deflation?
- Where wind removes dry, unconsolidated (loose) sand, silt, and clay particles from the surface and transports them away.
What is a deposition?
- This occurs when the velocity of the wind decreases until it can no longer transport the grains it is carrying.
What are endorheic streams?
- Where rivers occupy drainage basins that are closed and do not flow out to the sea or other river but instead end inland in lakes or swamps.
What is erosion?
- The wearing away of the Earth’s surface by the mechanical action of processes of glaciers, wind, rivers, marine waves, and wind.
What is exfoliation?
- A process of mechanical weathering that results in the breaking, splitting, or peeling-off of the outer rock layers. Also commonly known as ‘onion skin weathering’.
What are exogenous streams?
- Rivers that originate external to the desert in adjacent highlands and more humid environment, flow from outside of the desert and pass through it.
What is isolation?
- The incoming solar radiation that reaches the Earth’s surface.
What is mass movement?
- The movement of material downhill under the influence of gravity, but may also be assisted by rainfall.
What is saltation?
- A process where sand-sized particles are transported by bouncing and hopping along the surface.
What is sediment?
- Any naturally occurring material that has been broken down by the processes of erosion and weathering and has then been transported and subsequently deposited by the action of ice, wind, or water.
What is surface creep?
- Where saltating particles return to the surface and hit larger particles that are too heavy to hop.
What is suspension?
- Transportation by wind where the smallest particles, generally less than 0.2 millimeters, are held in the air.
What is a thermal fracture?
- The weathering of rock resulting from their rapid and repeated heating and cooling.
What is transportation?
- The processes that move material from the site where erosion took place to the site of deposition.
What weathering?
- The breakdown and/or decay of rock at or near the Earth’s surface creating regolith that remains in situ and until it is moved by later erosional processes. Weathering can be mechanical, biological/ organic, or chemical.
What characteristics make up an Arabian desert?
- Almost entirely sandy, with some of the largest sand dune system in the world.
What is an Australian desert?
- Mostly sandy plains.
- Mostly stony surfaces
What is the Chihuahuan desert?
- High flat plateau with some stony surfaces and sandy soil, broken by mountain ranges and distinctive mesas.
What characteristics makeup Kalahari desert?
- Extensive sand dunes interspersed with gravel plains.
What makes up Mojave desert?
- A varied landscape including sandy soils, gravel pavements, and salt flats.
What makes up the Sahara desert?
- Vast ranges of dunes amongst mountains and rocky areas, and gravel plains and salt flats.
What characteristics make up the Thar?
- Mostly sand dunes with areas of gravel plains.
What is desertification?
- The persistent degradation of dryland ecosystems by human activities and by climate change.