Lecture 11 flashcards

Question 1

What word means “deserted” or “unoccupied”?

Answer 1

Desert

Question 2

What are the two climactic types of dry lands that are commonly recognized?

Answer 2

Desert (AKA arid)
Steppe (AKA semi-arid)

Question 3

What’s this definition?
“climate in which yearly precipitation is not as great as the potential loss of water by evaporation”

Answer 3

Dry climate

Question 4

T/F: low-lying latitude dry climates are within he tropics of Cancer and Capricorn

Answer 4

True

Question 5

what desert occurs on the leeward side of mountains?

Answer 5

Rain shadow deserts

Question 6

What does chemical weathering look like for humid region deserts?

Answer 6

sleeps and rock edges being rounded

Question 7

What does mechanical weathering look like for deserts?

Answer 7

unaltered rock and mineral fragments

Question 8

T/F: in dry lands, rock weathering of any type is greatly reduced because of the lack of moisture and the scarcity of organic acids from decaying plants

Answer 8

True

Question 9

T/F chemical weathering is completely lacking in deserts

Answer 9

false - clays and thin soils DO form

Question 10

What is “desert varnish?”

Answer 10

rust-coloured stain created from the oxidation of many iron-bearing silicate minerals (weathering)

Question 11

Where do the few permanent streams across arid regions that originate outside the desert actually form?

Answer 11

well-watered mountains

Question 12

T/F: running water does most of the erosional work in deserts

Answer 12

true

Question 13

T/F: most landforms are carved by wind

Answer 13

False - water

Question 14

the main role of wind is ________ and _______ of sediment

Answer 14

transportation and deposition

Question 15

What are the two ways wind differs from water (in terms of entrainment/transportation)

Answer 15

1. Wind’s lower density compared with water renders it less capable of picking up and transporting coarse materials
2. Because wind is not confined to channels, it can spread sediment over large areas (and high into the atmosphere)

Question 16

Describe the action of creep in deserts (relates to bedload)

Answer 16

some sand grains are too large to be thrown into the air by impact from other particles
Energy provided by the impact of the smaller saltating grains drives the larger grains forwards

Question 17

what particles are carried in suspended load by wind?

Answer 17

silt and clay

Question 18

T/F: Dust is commonly composed of rather flat particles that have large surface areas compared with their weight – easy for turbulent air to keep fine particles airborne for hours or even days

Answer 18

true

Question 19

_______: lifting and removal of loose material by winds

Answer 19

deflation

Question 20

______: depression excavated by wind in easily eroded material

Answer 20

blowout

Question 21

____: a layer of coarse pebbles and gravel created when wind removes the finer material

Answer 21

desert pavement

Question 22

____: created by sand abrasion – side of stone exposed to the prevailing wind is abraded, leaving it polished, putted and with sharp edges

Answer 22

Ventifacts

Question 23

_______: “steep bank” – a streamlined, wind-sculpted ridge (like an inverted ship’s hull) oriented parallel to the prevailing wind

Answer 23

yardangs

Question 24

What are the two significant types of wind deposits?

Answer 24

1. Dunes: mounds and ridges of sand from the wind’s bed load
2. Loess: extensive blankets of silt that were once carried in suspension

Question 25

what's the angle of repose for dry sand?

Answer 25

34 degrees

Question 26

the leeward slope of a dune is also called the...

Answer 26

slip face

Question 27

Name that dune: * Solitary sand dunes, crescent-shaped with tips pointing downwind * Form where sand is limited and surface is relatively flat, hard, little vegetation * Largest reach 30m high, max spread of horns is 300m * Wind direction is constant = crescent is symmetrical * Wind direction isn’t fixed = one tip can become larger than the other (asymmetrical)

Answer 27

Barchan dune

Question 28

Name that dune! * Prevailing winds are steady, sand is plentiful, vegetation sparse or absent * Series of large ridges separated by troughs and oriented at right angles to the prevailing wind * Many coastal dunes * Common in arid regions where extensive surface of wavy sand is sometimes called a sand sea * Sahara and Arabian deserts – heights of 200m, 1-3km across, extend +100km

Answer 28

Transverse Dune

Question 29

Name that dune! * Long ridges of sand that form parallel to the prevailing wind where sand supplies are moderate * Prevailing wind direction must vary somewhat but still remain in the same quadrant of the compass * Parts of N Africa, Arabia, Central Australia – can reach +100m high and extend >100km

Answer 29

longitudinal dunes

Question 30

Name that dune! * Form where vegetation partially covers the land * Shape resembles barchans except their tips point to the wind * Often form along coasts where there are strong onshore winds, abundant sand and vegetation covering sand * The vegetation anchors parts of the sand (U or V shape is made) * Sparse vegetation at one spot, deflation causes a blowout * Sand is transported out of the depression and deposited as a curved rim, grows higher as deflation enlarges the blowout

Answer 30

Parabolic dunes

Question 31

Name that dune! * Confined largely to parts of Sahara and Arabian deserts * Isolated hills of sand that exhibit a complex form * Name derived from their bases, resemble multi-pointed stars * Usually 3-4 crescent shaped ridges that diverge from a central high point in some cases reach up to 90m high * Develop where wind directions are variable

Answer 31

Star dunes

Question 32

____: the deposits of windblown silt that lack visible layers, are generally pale yellow-brown and are capable of maintaining a nearly vertical cliff

Answer 32

Loess