dryland landforms Flashcards
wadis
dry riverbeds or valleys found in arid and semi arid regions.
formed by the erosion of mountains and hills and carry water during times of heavy rainfall or snowmelt
provide habitat for variety of plant and animal species
- formed by erosion and transportation of sediment by water.
canyons
deep, narrow valley with steep sides gorge, typically carved by a river or stream.
diverse array of animal and plant life and is very good for tourism, including hiking, camping, rock climbing……
formed by fluvial erosion, tectonic activity
pedestal rocks
large rock that sits on top of a smaller elevated base.
the erosional processes act much slower at the top more than at the bottom, therefore the bottom would be much more narrow.
due to the multiple layers of rock with different erosion resistances
mainly formed by aeolian processes, from wind carrying sediment and the slow eroding of the pedestal rock
ventifacts
rock that is formed by wind erosion. abrasion
found in desert regions with high winds. (near coasts)(prevailing winds)
barchans
crescent shaped sand dune
formed buy aeolian deposition, from winds blowing in one direction.
gently sloping windward side and a steep leeward side
small in size about 100 metres long and a few metres high
linear sand dunes
longer than they are wide
formed by prevailing winds in a consistent direction
occur in ergs (sandy deserts)
expand about the breakdown of the rocks into fine sand able to be carried in the wind
star dunes
sand dune shaped like a star with arms radiating outwards
formed by wind blowing from multiple directions, causing sand to accumulate in a star formation
found in deserts with an abundance of sand, wind blown from different directions and an area where there is a topographic barrier such as a mountain.
can be 500 metres high
alluvial fans and bajadas
bajada is the convergence of many alluvial fans
- formed when a stream loses velocity and the ability to transport sediment
-sediment (silt, clay, sand, gravel) are deposited on the plan and forms a fan shaped deposit
- sediment formed in layers with larger particles (gravel) at the bottom and smaller, finer particles (silt) at the top
- as the stream continues to deposit sediment, the alluvial fan grows larger in size.
common in arid and semi arid regions where the stream has a steep gradient and high sediment load and where the plan is relatively flat.
pediments
plain of low relief formed by running water at the base of a receding mountain
- formed by
- rainfall and weathering causing upper layers of the rock to be eroded away
- leaving the more resistant rock such as granite as a flat surface at the base of the mountain
- overtime it is shaped and smoothed by wind and water erosion
inselberg
steep, isolated hill / small mountain that rises from a flat plain. composed of hard, resistant rock such as quartzite and granite.
formed by tectonic uplift, erosion and weathering.
found in the great basin desert of nevada and utah
earths crust pushed upward due to tectonic uplift along fault lines.
overtime, surrounding rock and soil is worn away leaving inselbergs standing as an isolated peak.
made of hard more resistant rock, therefore freeze thaw cycles, heat expansions and contraction occurs at a much slower rate
frost shattered debris
jagged angular debris caused by freeze thaw cycles
- water enters into cracks and joints
- as temp drops below freezing, water in cracks freeze and expand
- expansion causes the rock to crack and break apart
- as rocks break apart, it forms jagged, angular pieces of debris.
found in talus slops and boulder fields
nivation hollows
small bowl shaped depression that form in areas where snow and ice accumulate
formed by erosion caused by freeze thaw of snow and ice
- snow accumulates in a depression like area, (small valley)
- as snow melts and re freezes, expands and contracts causing soil to be pushed upwards around the edges of the depression
- water from melted snow and ice flow through soil, eroding sides of the depression.
- overtime as the depression deepens and widens, it forms a bowl shaped nivation hollow
desert pavement
solifluction deposits
