D:Hot and Semi-Arid Environments

Question 1

What are the 4 different types of desert landscapes

Answer 1

1. Mountain Deserts
2. Sand Deserts
3. Shield Deserts
4. Stony Deserts

Question 2

Characteristics of a mountain desert

Answer 2

• Exposed bedrock
• Steep surfaces
• Upland with desert lake basins and salt flats
• e.g. Ksar Plateau, Tunisia

Question 3

Characteristics of a sand desert

Answer 3

the presence of ergs (broad flat area covered in sand).

• Vegetation is rare
• Desert likely formed during a pluvial period
• e.g. The Sahara

Question 4

Characteristics of a stony desert

Answer 4

• Sediment has been removed by deflation
• Bigger pebbles and rocks get left behind forming a desert pavement
• e.g. Syrian-Jordanian Desert

Question 5

Characteristics of a shield desert

Answer 5

• Hamada (bare rock plateau surfaces)
• Scattered rock fragments
• e.g. Chott-el Djerid, South Tunisia

Question 6

Define Equifinality, in terms of landforms

Answer 6

They are landforms that look similar but have been formed in different ways

Question 7

What are the 5 erosional landforms due to wind

Answer 7

1. Deflation Hollows
2. Ventifacts
3. Rock pedestals
4. Zeugen
5. Yardangs

Question 8

What are the 8 erosional landforms due to water

Answer 8

1. Wadi
2. Arroyos
3. Canyons
4. Mesas
5. Buttes
6. Inselbergs
7. Surface Crusts
8. Pediments

Question 9

What is a deflation hollow

Answer 9

Large enclosed surface depressions that have been created by the removal of large amounts of loose particles by the wind.

Question 10

What is a ventifact

Answer 10

Individual rocks with sharp edges

Question 11

What is a rock pedestal

Answer 11

Mushroom shaped rocks that occur where an isolated rock has been eroded more rapidly as the base, causing it to have a top-heavy shape.

Question 12

What is a Zeugen

Answer 12

A narrow ridge of land, with protective cap rock above it

Question 13

What is a Yardang

Answer 13

They are steep-crested, linear ridges of clay/rock. They consist of parallel troughs, separated by regular ridges

Question 14

What’s the difference between sheet floods and flash floods

Answer 14

Sheet floods are overland flow of water during heavy rainfall, while flash floods tend to occur in channels

Question 15

What is a Wadis

Answer 15

A dry river bed that form temporary channels following periods of heavy rain. Most are ephemeral rivers, with steep sides and a wide channel floor. e.g. Atlas Mountains Morocco

Question 16

Formation of Wadis

Answer 16

1. Formed during flash floods in a steep and smooth landscape
2. The floods cut the rills and widen them into gullies
3. The streams of water then widen the gullies to form steep sided valleys known as Wadis

Question 17

What is an Arroyo

Answer 17

Its a dry riverbed or seasonally active creek. They completely dry up during dry periods and are filled with water and become active again after substantial rainfall

Question 18

How do Arroyo’s form

Answer 18

1. Most arroyos form as a result of flash-flooding. The flash flood cuts through the dry ground to create these geological formation
2. Ephemeral streams,which are rivers that flow intermittently, often generating high discharge
3. The impermeable surfaces, lack of vegetation and particles being displaced by rain splash all reduce the infiltration rate
4. Due to these minimal infiltration rates the collective runoff eventually becomes concentrated into deep sided ravines called arroyos

Question 19

Whats the difference between an Arroyo and a Wadis

Answer 19

They form in the same way but an Arroyo is narrower

Question 20

What is a Canyon

Answer 20

Canyons are desert gorges, much deeper version of wadis. They have steep often vertical sides cut into resistant rock

Question 21

What is a Mesas

Answer 21

An elevated area of land with a flat top and sides that are usually steep cliffs. It takes its name from its characteristic table-top shape. Often bordered by steep canyons

Question 22

How does a Mesas Form

Answer 22

1. Through weathering and erosion of horizontally layered rocks that have been uplifted by tectonic activity. Differential erosion is what gives mesas their distinct shape
2. LEss resistant rocks are eroded away on the surface into the valleys, while the more resistant layers are left standing

Question 23

What is a Butte

Answer 23

An isolated hill with steep, often vertical sides and a small relatively flat top. Similar to a mesa but smaller and represent a more advanced stage of landscape development

Question 24

Formation of a Butte

Answer 24

1. Form when hard cap rock overlies a layer of less resistant rock that is eventually worn away
2. As the top is further eroded, the excess material that falls adds to the scree around the base

Question 25

What is an inselberg

Answer 25

Isolated relict hills of resistant rocks that are more rounded than mesas and buttes

Question 26

What is a surface crust

Answer 26

Extensive areas of flat or gently sloping desert surfaces covered with a mantle of weather debris

Question 27

Formation of a surface crust

Answer 27

1. Formed due to the transportation of fine particle by wind 2. Repeated wetting and drying- when wet there is no removal by wind and stones are pushed towards the surface. When dry, particles are removed and fine particles move down filling spaces left by stones that had risen before 3. They are the end product of surface deflation by wind and selective stone sorting by moisture

Question 28

What is a pediment

Answer 28

They are gently sloping erosional rock surfaces, with an angle of less than 7 degrees, found at the foot of mountain ranges

Question 29

How do pediments form

Answer 29

1. Formed by the parallel retreat of the slope of a plateau 2. As they retreat they leave behind a gently sloping rock platform 3. Parallel retreat occurs because rock is removed from the base of steep slopes at the same rate it is weathered

Question 30

Name the depositional and transportational landforms by wind x6

Answer 30

1. Barchans/Crescent 2. Transverse 3. Seifs 4. Longitudinal/Linear 5. Star 6. Draa

Question 31

What does Dune morphology depend on

Answer 31

1. Sand availability 2. Wind strength, direction and duration 3. Vegetation type and amount 4. Ground surface roughness

Question 32

What is a Barchans/Crescent dune

Answer 32

they have 3 characteristics: 1.Crescent shaped 2. Formed of desert sand 3. Always point towards the wind Material is moved by saltation and surface creep up the windward side, it then slides down the steeper leeward side Usually found around shrybs as they act as anchors to hold the central area in place

Question 33

What is a transverse dune

Answer 33

Resemble ocean waves, they are long, with wavy ridges. They are arranged in rows which are parallel and lie a right angles to the direction of the wind To cause this type of dune there has to be steady trade winds

Question 34

What are seif dunes

Answer 34

Long narrow dunes that form in ridges, shapeddue to winds blowing in 2 directions

Question 35

What are Star dunes

Answer 35

Pyramidal in shape they are the tallest dune, caused by winds coming from many different directions

Question 36

What are draa dunes

Answer 36

They are a sequence of large star dunes forming a ridge

Question 37

What are longitudinal/linear dunes

Answer 37

Form when Barchan dunes become highly elongated, but are very rare

Question 38

Name the 5 depositional and transportational landforms by water

Answer 38

1. Alluvial fans 2. Bajadas 3. Playas 4. Washes 5. Salt Flats

Question 39

What is an alluvial fan

Answer 39

Triangular fan shaped depsoits of water transported material, known as alluvium. Generally form in mountainous regions, where there is a sudden change in gradient

Question 40

Formation of an alluvial fan

Answer 40

1. As flowing water travels down a slope to a lowland, the velocity of the water decreases and it will spread out into a fan shape 2. As the river slows and loses energy, it despoits alluvium, the largest sediment first 3. Depostion is aided as the stream isn't confined to valley walls

Question 41

What is a Bajadas

Answer 41

Created where a number of parallel wadis arrive at the mountain front, causing a series of alluvial fans to join together, creating a continuous apron of sediment covering the lower slopes

Question 42

What is a playas

Answer 42

Hollows on the land surface, that may be occupied by hallow ephemeral saline lakes. The water in the lakes build up, but water is only retained for a short duration

Question 43

What is a desert wash

Answer 43

They are the drainage areas in desert terrains. Runoff scours the lowest lying areas, creating dry beds of loose sandy soil which are desert washes

Question 44

What is a salt flat

Answer 44

As the water leaves the lake through evaporation, it leaves behind deposits of soluble salts that were carried in solution. These