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Erosion
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To grow, corals need:

Clear, warm, shallow water

Wave action

Corbis Digital Stock

Slide 24

Coral reefs

Coral reefs

Fringing reef - directly attached to an island or coast

Barrier reef - lagoon between coast and reef

Atoll reef - circular reef surrounding a lagoon (no land in centre)

Slide 25

Aeolian (Eolian) landscapes

Aeolian (Eolian) landscapes

Wind erosion, transport and deposition

Occurs in dry regions, with little vegetation such as deserts and coastal landscapes

Slide 26

Wind Erosion

Wind Erosion

Faster the air flows, more erosion

Erodes more rapidly if wind blows constantly from one direction

2 TYPES OF WIND EROSION

ABRASION and DEFLATION

Slide 27

Deflation hollows

Deflation hollows

Removal of fine particles by wind leaves hollows behind (DEFLATION HOLLOWS)

Also leaves a surface of closely packed stones (DESERT PAVEMENT)

Slide 28

Wind transportation

Wind transportation

- Very fine material may be carried in suspension in the air

- But larger particles may be moved by 2 methods:

SURFACE CREEP &

SALTATION

Slide 29

1.) SURFACE CREEP

1.) SURFACE CREEP

- material is rolled along the surface

- accounts for 20% of wind transport

Slide 30

2.) SALTATION

2.) SALTATION

- The asymmetrical bouncing of sand grains

- Accounts for 80% of wind transport

- Cause of shifting sand dunes

Slide 31

Aggradational land forms

Aggradational land forms

SAND SEAS (ERGS)

= only 25% of the world's deserts

surface may be covered in RIPPLES

Slide 32

Sand dunes

Sand dunes

are ridges of wind deposited sand

- Usually 3 to 15 metres high, but can reach 180 metres

- A continuously changing dune is ACTIVE

Corbis Digital Stock

Slide 33

The formation of dunes depends on:

The formation of dunes depends on:

- amount of sand

- speed and direction of wind - occurrence of vegetation

Corbis Digital Stock

Slide 34

wind direction

wind direction

BACKSLOPE

SLIPFACE

movement of sand

angle of repose

crest

Slide 35

Types of sand dune

Types of sand dune

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