GEOMORPHOLOGY (EOLIAN) Flashcards
Desert
places with at most 25cm of precipitation
Of dry places in which yearly precipitation is less than the potential loss through evaporation
Extremely Arid
12 consecutive months w/o rainfall
Arid
<250mm annual rainfall
Semi Arid
250-500 mm mean precipitation
Deflation
actual removal of grains thus affecting only those unsconsolidated or loose ones
Abrasion
polishing and scouring of rock surfaces
Saltation
loose material remove from a bed and carried by air or water then return again to the surface
Creep/Rolling
Large particles are too heavy to be lifted are rolled across the surface with the momentum gained from the impact of jumping san particles
Suspension
Very fine grained dirt and dust are lifted into the wind
Reptation
when grains in motion collide, they become more easiliy moveable at a lower wind velocity compared to the velocity needed to move them by wind alone
The process of saltating grains releasing splash-like shower of particles that make small hops from the point of impact
Dust or stand storm
A meteorological Phenomenon that occurs in arid to semi-arid regions which arise when a gust form or other strong wind blows loose sand and dirt from a dry surface
Dust or Sand Devils
smaller, brief whirldwind most frequent in the early afternoon when a land surface is heating rapidly
Sedimentation
occurs simply when grains fall out of air or stop creeping forward
Accretion
occurs when saltating grains hit the ground with such force that some grains come to rest where they strike
Encroachment
Deposition that occurs on a rough surface creeping grains are held up while saltating one may move on
Ventifacts
Cobbles or pebbles on stony desert surface often faceted due to wind abrasion
Hamada
Rocky desert lag consist of corase rocks
Desert Pavement or Reg
Surfaces covered by lag deposits
Desert Varnish
Dark, surface patina of iron and mangangese oxides
Lag deposits
thin veneers of gravel or coarser materials overlying finer ones
Blowouts
commonest landforms produced by win erosion which are scoured depressions in weark unconsolidated sediments
Pans
Closed depressesions that are common in dryland areas partly formed by deflation
Few meters wide only cm deep
Yardangs
spectacular streamlined, sharp and sinuous ridges parallel to the wind and separated by parallel depressions
Zeugen
Redisual blocks of rock produced by wind earting away strata esp. the soft ones close to the ground
Loess
Wind-blown silt blankets
Dunes
Mounds and ridges of sand from the winds bed load
Aeolianites
Lithified wind blown carbonate deposits
Erg
Sandy Deserts
Or dry areas with large acummulation of sands
Aeolian Ripples
small aerolian bedform with heights of less than a cm to more than ten cm
Transverse Dunes
Straight crested forms aligned perpendicular to the prevailing uniformly wind direction
Barachnoid
Long sysmmetrical dunes perpendicular to the prevailing wind
Consist of joined barchans and looks like row of connected crescents
Intermediate between tranvese and Barchan
Barchan Dunes
Cresent shaped dunes perpendiculat to the dominant wind direction
Tips/Points/ends or wings are curved downwind parallel to the wind direction and enclose the slip face
Parabolic Dunes
Long axis is perpendicular to the wind
Wings or points are curved upwind opposite to the direction of the wind
Have multiple slip faces
Occurs near coasts and in areas of vegetation
Linear or Seif
two prominent wind direction at 90 deg to each other
Corss bedding avalanching down both sides of the dunes
Ridge is parallel to the wind while theres two opporiste slip face
Star
Slip faces in many orientations hence cross bedding directions are also variable
Draa
Sandy bedforms which are larger in magnitude than dunes reaching up to 400 m high and sit up to 4km spacing
Zibar
corase grained bedform of low relief and possessing no slip face. also known as whaleback dunes
Sand Sheets or Streaks or Stringer
Large bodies of sand with no discernible dune forms
Dunefield
At least 10 dunes
Nabkha
Vegetated Sand mound
