Arid Lands

Question 1

Special Desert Conditions

Answer 1

1) Weathering = only mechanical since no water for chemical
2) Soil/Regolith = thin + absent in most places –> lack of soil
3) hardpans widespread –> soil impermeable to water
4) sand = water infiltrates ground + easily moved by heavy winds
5) limited rainfall creates short-distance temporary streams + lack of vegetation
6) underdeveloped drainage systems

Question 2

Weather type in arid regions

Answer 2

1) B climates

Question 3

Main agent of erosion

Answer 3

WATER even in arid landscapes

Question 4

Exotic Streams

Answer 4

1) exotic - water in stream comes from outside desert, usually from higher mountain area
2) ex = Nile River = water comes from mountains of Africa/Ethiopia
3) able to sustain itself through arid environments

Question 5

Ephemeral Streams

Answer 5

1) carry water only seasonally or after rainstorm
2) when carries water = intense erosion, transportation, deposition
3) dry beds of ephemeral streams –> flat floors, sandy bottoms, steep sides

Question 6

Playas

Answer 6

1) Dry lake beds (occasionally fill with water)
2) high salinity bc of evaporation of water

Question 7

Saline Lakes

Answer 7

1) Permanent desert lakes BUT extremely high saline concentrations –> much more evaporation of water compared to inflow

Question 8

How does fluvial erosion begin in desert

Answer 8

1) Begins with brief but intense thunderstorm
2) lots of water on ground BUT bc most of desert soil is impermeable –> water runs off into nearby ephemeral stream
3) fills up with water –> creating flash flood + debris flow

Question 9

Flash Flood Hazard in desert

Answer 9

1) Risk to humans in arid lands
2) Desert cities –> flood-control channels + basins

Question 10

Differential weathering effect in arid landscape

Answer 10

1) striking difference in erosion + weathering bc of sparse cover of soil/vegetation
2) Rocks resistant to weathering –> form cliffs, pinnacles, spires (pointy stuff) while less resistant rocks form gentle slopes

Question 11

Fluvial Deposition

Answer 11

more common than fluvial erosion, most prominent along piedmonts (base area around mountains)

Question 12

alluvial fan

Answer 12

1) Deposition of sediment in piedmont zone
2) occurs because river goes from flowing through mountain gorge into an open piedmont zone (water spreads out –> reduced CC –> drops sediment)

Question 13

Aeolian processes

Answer 13

1) Related to wind action
2) most pronounced + effective in regions with fine grain sand + little vegetation and moisture (deserts_

Question 14

2 divisions of Aoelian erosion

Answer 14

1) deflation
2) abrasian

Question 15

Deflation

Answer 15

1) loose particles blown through air or along ground –> moved by deflation
2) GENERALLY wind not strong enough to move anything more than dust/sand grains

Question 16

Blowout (deflation hollow)

Answer 16

1) shallow depression where abundance of fine material has been deflated
2) generally 1 mile in diameter

Question 17

Abrasion

Answer 17

1) similar to fluvial abrasion BUT much less effective
2) the sand/dust hitting rocks results in pitting, etching, faceting, polishing of exposed rock surfaces (ventifacts)
3) found in mesa-and-scarp regions

Question 18

Aeolian Transportation

Answer 18

1) finest particles carried in suspension as dust
2) larger particles moved through saltation + traction (like streamflow)

Question 19

Unanchored dunes

Answer 19

1) moved by local winds
2) force sand up + over crest (on windward side)
3) goes onto leeward side (slip face) which has a 32-34 degree angle of repose

Question 20

Anchored dunes

Answer 20

1) held in place by vegetation BUT they do not provide much nourishment/moisture for plant growth

Question 21

Types of dunes

Answer 21

1) Barchan
2) transverse
3) seif (longitudinal)
4) star

Question 22

Sheltered Pocket

Answer 22

On opposite side of dune (opposes wind direction)

Question 23

Barchan dunes

Answer 23

1) Crescent shaped + formed bc of strong winds blowing in one direction
2) fastest moving dunes

Question 24

Transverse Dunes

Answer 24

1) less crescent shaped + occur where entire landscape is sand-covered
2) much more sand than barchans
3) looks like ripples of water

Question 25

Seif (longitudinal)

Answer 25

1) Long, narrow + generally parallel
2) created by two dominant wind directions blowing in one direction half of the year and another direction the other half

Question 26

Star Dunes

Answer 26

1) pyramid shaped dunes that are star shaped
2) formed in areas where wind constantly changes directions

Question 27

Basin-and-range terrain features

Answer 27

1) ranges
2) piedmont zones
3) basins
basin-and-range place without external drainage + some exotic rivers

Question 28

How did basin + range topography form

Answer 28

1) repeated process caused by tension forces (inactive rifts)

Question 29

Ranges

Answer 29

1) rugged mountain ranges in all directions
2) tend to be long, narrow, parallel to one another
3) have alluvial fans (V-shaped cross sections)

Question 30

Piedmont Zone

Answer 30

1) Base of ranges –> zone of transition between steep range slopes to flatness of basin
2) full of alluvial fans + bajadas

Question 31

Bajada

Answer 31

1) interconnected alluvial fans
2) as deposition occurs, fans grow larger + interconnect

Question 32

Basins

Answer 32

1) Beyond flattish floor –> gently slopes from all sides to low point (usually playa)
2) poor drainage channels
3) salt accumulation common around the playa –> becomes salina if there is enuf salt

Question 33

Mesa-and-Scarp Terrain

Answer 33

1) Tall, steep vertical cliffs in the Four Corners Country (Colorado, Utah, Arizona, New Mexico)
2) Grand Canyon

Question 34

Weathering of mesa-scarp formation

Answer 34

1) horizontal + sedimentary strata
2) each level has different degrees of erosion which causes abrupt changes in slope angle
3) most resistant layer = at bottom = scarp
4) alternates between scarp + inclined + scarp + inclined
5) top scarp = mesa

Question 35

Plateaus

Answer 35

1) Extensive elevated flatlands of uniform horizontal layers

Question 36

Progression from plateau

Answer 36

1) Plateau –> mesa –> butte –> pinnacle
2) each consecutive is smaller + more eroded

Question 37

Badlands

Answer 37

1) rugged, heavily eroded landscapes
2) lots of ravines + gullies formed by overland flow from rain (effective erosive agent)