What are the three main sources of energy in desert systems?
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What are the three main sources of energy in desert systems?
The three main sources of energy in desert systems are insolation, wind, and precipitation runoff.
True or False?
Deserts have low rates of evaporation due to high insolation.
False.
Deserts have high rates of evaporation due to high insolation.
What is the Harmattan?
The Harmattan is a dry and dusty West African trade wind that blows south from the Sahara into the Gulf of Guinea between November and March.
Define sediment budget.
A sediment budget is the balance between the relative amounts of sediment gained and lost within a particular desert system or sub-system.
What are the four components of a sediment cell?
The four components of a sediment cell are inputs, transfers, stores, and outputs.
True or False?
Most desert sediment derives from recent fluvial processes.
False.
The majority of desert sediment derives from ancient pluvial processes.
What is loess?
Loess is fine, wind-blown sediment, typically deposited far from its source.
What was the Tethys Sea?
The Tethys Sea was an ancient sea that existed between the continents of Gondwana and Laurasia before the formation of the Sahara Desert.
True or False?
Large deserts can be a significant source of global sediment.
True.
Large deserts can be a significant source of global sediment, with dust from the Sahara being transported and deposited thousands of miles around the world.
What does active, mobile landscape mean in the context of deserts?
Active, mobile landscape in the context of deserts means that desert landscapes are constantly changing due to the inputs of wind, water, and insolation.
What are the two main forms of mechanical weathering in hot deserts?
The two main forms of mechanical weathering in hot deserts are thermal fracture and pressure exfoliation.
Define thermal fracturing.
Thermal fracturing, also called thermal exfoliation or onion skin weathering, is a process where rocks break down due to extreme daily temperature variations.
What is pressure exfoliation?
Pressure exfoliation, also known as pressure release exfoliation, is a process where rock fractures due to the removal of overlying pressure as erosion exposes deeper rock layers.
True or False?
Chemical weathering is the dominant form of weathering in hot deserts.
False.
Physical weathering is generally more dominant in hot deserts due to the lack of water.
What is granular disintegration?
Granular disintegration is a weathering process where rocks break down into individual grains, typically producing sand-sized material.
Define hydration in the context of weathering.
Hydration is a chemical weathering process where minerals in rocks absorb water and expand, causing stress and eventual breakage along joints.
What is crystal growth weathering?
Crystal growth weathering is a process where salt crystals grow in rock pores and joints, leading to the disintegration of the rock.
What is block disintegration?
Block disintegration is a weathering process where well-jointed and bedded rocks, such as limestone, break into blocks along natural weaknesses.
Define exfoliation.
Exfoliation is a weathering process where layers or sheets of rock peel off from the surface of a larger rock mass.
True or False?
Weathering in deserts occurs rapidly due to the presence of water.
False.
Weathering in deserts is generally slow due to the lack of water, with physical weathering being more dominant than chemical weathering.
What are the three main ways wind erodes in hot deserts?
The three main ways wind erodes in hot deserts are deflation, abrasion, and attrition.
Define deflation.
Deflation is the carrying and removal of loose material by wind.
True or False?
Attrition only occurs during wind transportation.
True.
Attrition occurs when wind-blown particles collide with each other during transportation, becoming smaller.
What is a deflation hollow?
A deflation hollow, also known as a blowout, is a depression in the desert surface formed by wind erosion.
Define desert pavement.
Desert pavement is a hardened desert floor formed when wind removes fine sediments, leaving behind coarser gravels and exposed bedrock.
What are the three ways wind transports material in deserts?
The three ways wind transports material in deserts are creep, saltation, and suspension.
What is saltation?
Saltation is the bouncing movement of sand particles close to the ground when wind exceeds threshold velocity.
Define threshold velocity.
Threshold velocity is the minimum wind speed required to initiate the movement of sand particles.
What percentage of deserts are covered in wind-blown sands?
Approximately 30% of all deserts are covered in wind-blown sand, forming erg deserts.
True or False?
Suspension can carry particles far from their source.
True.
Suspension can carry fine dust particles high into the atmosphere and far from their source, even to other continents.
What are ephemeral rivers?
Ephemeral rivers are intermittent streams that flow only after rainstorms or from snowmelt, also known as wadis, barrancas, washes, or arroyos.
Define endoreic rivers.
Endoreic rivers are rivers that flow into the desert but terminate in an inland lake or sea, without reaching the ocean.
What are exogenous rivers?
Exogenous rivers are large, perennial rivers with an external source that have sufficient discharge to flow continuously across arid land.
True or False?
Sheet floods occur when water is confined to channels.
False.
Sheet floods occur when water flows evenly over land and is not confined to channels.
What is splash erosion?
Splash erosion is the detachment and short-distance transport of soil particles caused by the impact of raindrops on bare soil.
What are the four main types of water erosion in deserts?
The four main types of water erosion in deserts are splash erosion, rill erosion, gully erosion, and bank erosion.
True or False?
Water plays an insignificant role in shaping desert landscapes.
False.
The impact of water is significant in shaping desert landscapes, despite its infrequent occurrence.
What is a relict feature in desert landscapes?
A relict feature is a landform created during past, wetter climatic periods that persists in the current arid environment.
Define sheetwash.
Sheetwash is the process of water flowing evenly over land in a thin sheet before becoming concentrated into channels.
True or False?
Infiltration rates are high in desert soils due to lack of vegetation.
False.
Infiltration rates are often low in desert soils due to surface compaction and the formation of crusts from raindrop impact.