Geo Final Chapter 21
Arid Land
10 inches of less of rain a year
Semiarid Lands
10-20 inches of rain a year
Extremely Arid Lands
12 consecutive months without rainfall
How do weathering processes in deserts differ from those in temperate or humid climates?
Chemical weathering happens slowly. Soils and rocks tend to accumulate soluble minerals
Explain several settings that can cause desert to form
Formed by rain shadows. Mountains block the patch of participation. Composed of rocky or sandy landscape
Desertification
Land abuse may transform semiarid land into deserts. The Sahara will grow and the Caribbean could get closer to arid landscapes
Have today's deserts always been deserts?
No, abuse of the land and land transformations have created and enlarged some deserts
What factors determine whether a region can be classifies as a desert?
Receive less than 25 cm of rain a year. Vegetation covers no more than 15% of their surface.
Describe the process of cliff (scrap) retreat and the landforms that result from it
When cliffs retreat due to erosion and weathering they become mesas, buttes, and isnelbergs
Explain the ways in which desert winds transport sediment...and deposition
Wind can also pick up silt and dust causing it to undergo saltation, can cause or shift deposition
Desert Varnish Formation
A dark, rust-brown coating of iron oxide and magnesium oxide that accumulates on the surface of the rock
Ventifacts Formation
A desert rock whose surface has been formed by the wind
Alluvial Fan Formation
A gently sloping apron of sediment dropped by an ephemeral stream of at the base of an arid region
Desert Pavement Formation
A mosaic-like stone surface forming the ground in a desert
Yardangs Formation
A mushroom-like column with a resistant rock perched on an eroding column of softer rock; created by wind abrasion in deserts where a resistant rick overlies softer layer of rock
Bajadas Formation
An elongate wedge of sediment formed by the overlap of several alluvial fans emerging from adjacent valleys
What are the various types of sand dunes?
Barchan, star, transverse, parabolic, and longitudinal
Playas Formation
The flat, typically salty lake bed that remains when all the water evaporates in drier times
What factors determine which type of dune develops at a particular location?
The location of other land formations, wind flow, etc.
Describe how water modifies the landscape of a desert...explain erosion
Water causes significant erosion in deserts, mostly in heavy downpours. Flash floods can occur