erosional features Flashcards
(22 cards)
What is non-glacial loess?
Loess that can originate from deserts, dune fields, playa lakes, and volcanic ash.
Name two types of non-glacial loess.
- Volcanic loess in Ecuador and Argentina
- Tropical loess in Argentina, Brazil, and Uruguay
What are deflation hollows?
Depressions caused chiefly by the removal of loose particles by wind.
What is a ventifact?
Rocks that have been abraded, pitted, etched, grooved, or polished by wind-driven sand.
Define deflation in the context of wind erosion.
The lowering of the land surface due to removal of fine-grained particles by the wind.
What is desert pavement?
A surface composed only of coarser grained fragments that cannot be transported by the wind.
What are barchan dunes?
Crescent-shaped mounds formed under winds that blow consistently from one direction.
What characterizes parabolic dunes?
U-shaped mounds of sand with convex noses trailed by elongated arms held in place by vegetation.
What is periglacial loess?
Loess derived from the floodplains of glacial braided rivers with high content of glacially ground flour-like silt and clay.
What is loess?
An aeolian sediment formed by the accumulation of wind-blown silt, typically in the 20–50 micrometre size range.
What are star dunes?
Pyramidal sand mounds with slipfaces on three or more arms that radiate from the high center of the mound.
What are seif dunes?
Longitudinal dunes that elongate parallel to the prevailing wind.
How is material transported by wind?
- Suspension for the finest dust and silt
- Saltation for slightly bigger grains
- Creep for larger particles
What defines a coastal desert?
Areas where cold upwelling seawater cools the air and decreases its ability to hold moisture.
What is a polar desert?
Cold polar regions where cold dry air prevails and moisture remains frozen throughout the year.
What are subtropical deserts?
Deserts where dry, subtropical air is brought into mid-latitudes.
What is a rainshadow desert?
Deserts formed where mountainous regions cause air to rise and condense, dropping moisture.
What are the four natural agents of erosion?
- Wind
- Water
- Moving ice (glaciers)
- Gravity
True or False: Wind is the strongest natural agent for erosion.
False
What is aeolian action?
Erosion, transportation, and deposition by wind.
What are yardangs?
Long narrow, parallel ridges and grooves sculpted by the wind.
Fill in the blank: Desert landscapes were once thought to be essentially wind formed, but later research suggested that major landforms were shaped by _______.
water
