Desert Landforms

Question 1

Wadi: example and processes

Erosional

Answer 1

Wadi Rum, Jordan

Abrasion and hydraulic action. Rill and gully erosion.

A dry riverbed eroded by occasional flash floods.

Question 2

Canyon: example and processes

Erosional

Answer 2

Grand Canyon, Colorado, USA

Abrasion, hydraulic action.

Deep, steep sided gorge, eroded vertically by exogenous rivers.

Question 3

Mesa and butte: examples and processes

Erosional

Answer 3

Monument Valley, Arizona-Utah

Abrasion, attrition, hydraulic action. Rill and gully erosion. Weathering exposes initial weaknesses.

Portions of plateau isolated from main plateau. More resistant cap rock on top.
Mesa (wide) Butte (tall)

Question 4

Inselberg: examples and processes

Erosional and weathering

Answer 4

Inselberg Mirabib, Namib Desert

Deep underground chemical weathering. Deflation and fluvial erosion.

Island mountain of resistant rock rising from the soft rock of the plain.

Question 5

Alluvial fan: examples and processes Erosional

Depositional

Answer 5

Death Valley, California

Milner Creek, California. 700,000 year old! (Pluvials)

Wadi/canyon meets the lower ground. Steep change in gradient- river loses energy- deposition.
Coalescing fans= bajada

Question 6

Pediment: examples and processes

Fluvial abrasion/ weathering

Answer 6

Colorado Desert

Theories:
1. Easy meanders near base of mountain
2. Sheetwash
3. Weathering of exposed mountain base

A shallow slope at the foot of a steep slope

Question 7

Salt lake: examples and processes

Answer 7

Salt Lake, USA

Evaporation of water leaves salt behind.
Weathering (thermal expansion, etc) forms cracks on the surface.

Question 8

Deflation pan/ depression: examples and processes

Aeolian erosion

Answer 8

Qattara Depression, Egypt

Deflation

Strong winds remove loose material to reveal basin of bed rock.
Eddies accelerate erosion.

Question 9

Desert pavement: examples and processes

Aeolian erosion

Answer 9

Gibber Plains, Central Australia

Deflation

Fine material is deflated, leaving a layer of coarse, heavier particles and pebbles.

Question 10

Rock pedestals: Examples and processes

Aeolian erosion

Answer 10

Monument Valley, Arizona

Deflation + abrasion

Resistant rock on top of less resistant. Abrasion occurs under 1 m, less resistant erodes faster, overhand collapses.

Question 11

Yardangs: examples and processes

Aeolian erosion

Answer 11

Boukou Region, Tibesti Mountains, central Chad

Vertical strata of more and less resistant rock. Deflation and abrasion of less resistant at faster rate by parallel prevailing wind. Ridges and troughs develop. 1m abrasion narrows bases. Eddies- increase turbulence and increase deflation.

Question 12

Alveoles: examples and processes

Weathering

Answer 12

Goblin Valley State Park, Utah

Chemical weathering e.g. carbonation and wetting and drying
PLUVIALS

Question 13

Star Dunes: e.g

Answer 13

Dune 7, Namib Desert

Yeah wind regimes, multiple winds from different directions, arms snake away from central point.

Question 14

Parabolic dunes e.g.

Answer 14

Peru

U shaped, concave, two anchor points, limited vegetation. Unidirectional wind.

Question 15

Transverse dunes e.g.

Answer 15

Kidds Beach, South Africa

Wave shaped. Develop at right angles to prevailing wind. Abundant sand, stabilised by vegetation.

Question 16

Barchan dunes e.g.

Answer 16

Grand Erg Oriental

Crescent shaped. One central anchor point. Saltation and creep transport grains up and over the dune.

Question 17

Linear dunes e.g.

Answer 17

Simpson Desert (near playa lakes)

Bidirectional converging winds.

Question 18

Reversing dunes

Answer 18

Soussevi National Park, Namibia

Two well marked seasonal winds, blowing in opposite directions.

Question 19

Aridisol soils

Answer 19

More capillary action
Low organic content
High pH
Water deficient

Question 20

Solonetz soils

Answer 20

More infiltration
Clay heavy
Colloids swell with water

Question 21

Solonchak soils

Answer 21

More cappilary action
Carbonates and chlorides heavy= thick infertile crust

Question 22

Desert soils are…

Answer 22

Saline, thin, alkaline

Question 23

Four types of thermal fracture/ expansion.

Answer 23

Granular disintegration (heterogenous e.g. granite, heat and cool at diff. Rates)

Exfoliation (large rock, frequent diurnal temp. Fluctuations)

Block disintegration (bedding planes, faults, sedimentary)

Shattering (homogenous + dark e.g. basalt)

Question 24

Venitfacts

Answer 24

Shaped by variety of different winds.
Large unmoving rock.
Abrasion smooths the sides.

Question 25

Ergs/ sand seas cover how much of SW USA vs Sahara?

Answer 25

1-2% 20%

Question 26

Erg example

Answer 26

The Empty Quarter of Arabia

Question 27

Hammada

Answer 27

Desert surface that is mainly large rocks

Question 28

Why do deserts have so much overland flow?

Answer 28

1. Lack of vegetation (decreased interception) 2. Thin soils (low organic matter, infiltration capacity exceeded) 3. Duricrust (sun-baked impermeable layer) 4. Rain splash erosion (more crust formation)