Naturalists at Large: deserts

Deserts & Winds Deserts & Winds

““We don’t survive the desert,We don’t survive the desert, we we live live here”here” - Pima Indian- Pima Indian

““We don’t survive the desert,We don’t survive the desert, we we live live here”here” - Pima Indian- Pima Indian

1) Deserts: where & why1) Deserts: where & whyDeserts & windsDeserts & winds

Earth’s dry regionsEarth’s dry regions: 30% of all land

2 climate types of dry regions:

desert desert (arid)

steppe steppe (semi-arid, surrounds deserts)

1) Deserts: where & why1) Deserts: where & whyDeserts & windsDeserts & winds

What causes deserts?What causes deserts?

air pressureair pressure windwind

Important factors:

Global distribution ofGlobal distribution of

rainfallrainfall evaporationevaporation

Relationship betweenRelationship between

www.weatherchannel.com

1) Deserts: where & why1) Deserts: where & whyDeserts & windsDeserts & winds

1) Deserts: where & why1) Deserts: where & whyDeserts & windsDeserts & winds

Low-latitude desertsLow-latitude deserts

Tropic of Cancer

Tropic of Capricorn

(recall: “latitude” = east-west line on the globe)

Equator: hot air rises to 15-20 km low pressure belt

In contrast….

1) Deserts: where & why1) Deserts: where & whyDeserts & windsDeserts & winds

1) Deserts: where & why1) Deserts: where & whyDeserts & windsDeserts & winds

1) Deserts: where & why1) Deserts: where & whyDeserts & windsDeserts & winds

1) Deserts: where & why1) Deserts: where & whyDeserts & windsDeserts & winds

Middle-latitude desertsMiddle-latitude deserts

exist in rain shadows.

2) Basin and range2) Basin and rangeDeserts & windsDeserts & winds

Basin and rangeBasin and range

mountainous desert landscape

2) Basin and range2) Basin and rangeDeserts & windsDeserts & winds

Basin and rangeBasin and range

mountainous desert landscape

3) Wind erosion/ deposits3) Wind erosion/ depositsDeserts & windsDeserts & winds

Wind erosion: Important in arid environments

Example: Types of sand dunes:

Sand dune shape depends on:

Flat or hilly?How much sand?Winds steady or intermittent?Wind direction constant?Vegetation present?

3) Wind erosion/ deposits3) Wind erosion/ depositsDeserts & windsDeserts & winds

Sand dune formation

3) Wind erosion/ deposits3) Wind erosion/ depositsDeserts & windsDeserts & winds

Desert pavement

3) Wind erosion/ deposits3) Wind erosion/ depositsDeserts & windsDeserts & winds

3) Wind erosion/ deposits3) Wind erosion/ depositsDeserts & windsDeserts & winds

Graded beds