Deserts And Wind

Front 1

Why do deserts exist?

Back 1

sinking air absorbs water so the ground surface is dry and rainfall is rare

Front 2

Define: Rain-Shadow Desert

Back 2

an arid zone created by warm, dry air on the downward side of a mountain range

Front 3

3 ways water can reach a desert

Back 3

1. streams flow from nearby mountains and bring surface water to desert areas

2. ground water can flow from a wetter source to an aquifer beneath a desert

3. occasional rain and snow fall

Front 4

Where do large rivers in deserts get their water?

Back 4

wetter, mountainous regions bordering the desert

Front 5

Define: Wash

Back 5

a streambed that is dry for most of the year

Front 6

Many desert lakes lie above the ____ _____

Back 6

water table

Front 7

Define: Playa Lake

Back 7

an intermittent desert lake

Front 8

Define: Playa

Back 8

dry lake bed of a playa lake

Front 9

Define: Flash Flood

Back 9

when a flood occurs because a dry streambed fills with water rapidly

Front 10

When does a mudflow occur?

Back 10

When rainfall is unusually heavy and prolonged

Front 11

Define: Alluvial Fan

Back 11

a fan-like accumulation of sediment created where a steep stream slows down rapidly as it reaches a flat valley floor

Front 12

Define: Bajada

Back 12

broad, gently sloping depositional surface formed by merging alluvial fans extending from each canyon

Front 13

When does an alluvial fan form?

Back 13

when a steep flooding mountain stream empties into a flat valley and deposits its sediment at the mountain front

Front 14

Define: Pediment

Back 14

broad, gently sloping surface eroded into bedrock

Front 15

Where do pediments form?

Back 15

along the front of desert mountains

Front 16

Define: Deflation

Back 16

wind erosion

Front 17

Wind only moves _____ _____

Back 17

small particles

Front 18

What are the common particles wind moves?

Back 18

Silt and sand

Front 19

Define: Desert Pavement

Back 19

a cover of stones left behind when the wind takes the sand

Front 20

Windblown sand is ____

Back 20

abrasive

Front 21

Define: Saltation

Back 21

in a windstorm, the sand grains bounce over the ground

Front 22

Define: Dune

Back 22

a mound or ridge of wind-deposited sand

Front 23

Dune form when:

Back 23

wind erodes sand from one location and deposits it nearby

Front 24

Define: Blowout

Back 24

saucer shaped hollow formed by wind erosion is

Front 25

wind erodes sand from the ______ side of a dune

Back 25

windward

Front 26

Define: Slip Face

Back 26

leeward face of a dune

Front 27

Define: Cross-bedding

Back 27

an arrangement of small beds at an angle to the main sedimentary layering

Front 28

Define: Barchan Dune

Back 28

a crescent shaped dune with tips pointing downward and a center that grows higher than the edges

Front 29

Define: Transverse Dunes

Back 29

long ridges aligned perpendicular to the prevailing wind

Front 30

Define: Parabolic Dune

Back 30

similar in shape to a barchan dune, except that the tips of the parabolic dune point into the wind resulting from wind being carried out of a blowout

Front 31

Define: Seif Dunes

Back 31

long, straight dunes parallel to the prevailing wind

Front 32

Define: Star Dunes

Back 32

pyramidal sand mounds with slipfaces on three or more arms that grow upwards not outwards

Front 33

Define: Loess

Back 33

a homogenous, unlayered, porous deposit of windblown silt

Front 34

When do loess form?

Back 34

when silt-sized particles are usually deposited at the edge of the desert

Front 35

Define: Erg

Back 35

broad, flat area of desert covered with wind-swept sand

Front 36

What forms natural arches?

Back 36

erosion from wind and water, as well as from the weathering effects of salt and frost

Front 37

Define: Vetifacts

Back 37

stones shaped by the erosive action of windblown sand

Front 38

Define: Mud Cracks

Back 38

edimentary structures formed as muddy sediment dries and contracts