Deserts and Wind

Question 1

Why is it hard to have larger populations of animals in deserts?

Answer 1

Low vegetation and not enough water

Question 2

Why is the temperature always high in deserts?

Answer 2

The atmosphere in desert regions contains very little humidity, so there’s nothing to block the sun’s rays or retain heat at night; deserts also have very low precipitation

Question 3

How do deserts form?

Answer 3

Air warms and contracts as it sinks closer to Earth’s surface, evaporation exceeds condensation, and the desert forms (around 30N and 30S latitudes)

Question 4

Factors determining desert formation

Answer 4

• orographic effect (a very high mountain will block the rainclouds from getting through to the other side of the mountain, leaving that side in the “rain shadow” and arid conditions)
• dry, cold air descending over polar regions
• the distance atmospheric moisture is transported
• cold ocean current adjacent to a tropical coast
• poor management of farmland
• deforestation

Question 5

Suspension during dune movement

Answer 5

Silt carried in suspension produces well-sorted deposits of progressively smaller sediments with distance

Question 6

Loess

Answer 6

Eolian (deposited by wind) fine grain material: silt and clay that has been moved and deposited by wind

Question 7

Desert Pavement

Answer 7

Lag deposit of coarse sediment left after fine sand blows away

Question 8

Yardang

Answer 8

Rock outcrop sculpted by sand abrasion

Question 9

Factors that contribute to the creation of dunes / what you need to create a dune

Answer 9

1. Abundant loose sediment (sand or finer)
2. Energy to move sediment (air, sometimes water)
3. An obstacle to trap sand (often a bush; sand needs to speed up, then slow down)
4. A dry climate

Question 10

Barchan (Crescentic Dune)

Answer 10

Strong wind in one direction, small amounts of sand, limited vegetation (Look like U-shaped hills)

Question 11

Transverse dunes

Answer 11

Weak wind in one direction, large amounts of sand deposited perpendicular to the wind, limited vegetation

Question 12

Parabolic Dunes

Answer 12

Arms stabilized upwind by vegetation, often start as semi-circular blowouts that elongate (Look like an upside-down U-shaped hills)

Question 13

Longitudinal Dune

Answer 13

Winds flowing in opposite directions, two slip faces, aligned with the wind

Question 14

Star Dune (rare)

Answer 14

Multidirectional winds, largest dunes, grow tall instead of moving (grow in height, not width)

Question 15

Sand Seas

Answer 15

Large regions (>125km2) of windblown sand numerous, very large dines, sand covers more than 20% of the ground surface

Question 16

Arid Landforms

Answer 16

• shaped by water
• flash floods are common
• streams tend to be ephemeral (they come and they go), flowing only after heavy rain

Question 17

Paya Lakes

Answer 17

Products of rainfall and evaporation, leaves the ground covered with mudcracks

Question 18

Desertification

Answer 18

The process by which land loses its vegetation and turns into a desert