1. The Work of Waves and Wind
• Objectives:
• Explain the characteristics of ocean waves
and tides
• Present coastline features of erosion,
transport and deposition
• Examine the processes of wind erosion and
deposition
• Differentiate different types of dune
• Describe the wind deposit LOESS

2. COASTAL LANDFORMS
wave length
crest
wave trough
height particles in
waves follow a
circular pattern

3. At the shoreline
• Water becomes shallow, wave height increases
because wave length decreases
• Waves become steeper, then collapse (breakers)

4. • Surf - sequence of
breaking waves
• Swash - water
sliding up beach
• Backwash - water
flowing back down
beach to sea

5. Wave refraction
• Close to coast, water gets more
shallow
• Waves are slowed down
• If waves arrive at an angle, one part
is slower than the rest
• Causes waves to bend = wave
refraction

6. Wave refraction
Bay
Headland

7. • Waves arriving at bays are slow (deposition)
• At headlands, faster (erosion)

8. • A sequence of
features is
produced as
headlands are
degraded
• Sea cliffs
• Waves erode
base the cliff
-undercutting
retreats

9. • Also produces
sea caves
• As cliffs retreat
produces a wave-
cut platform

10. • Headlands
may be eroded
back leaving a
remnant (stack)
stack

11. Longshore drift
• Waves arrive at a coast
at an angle (swash)
• Backwash returns at 90
degrees
Sand is moved along the beach = longshore
drift or longshore current

12. Coastal deposition
• Result of
longshore drift and
a lot of sediment
• = produces
extensions of
deposit from the
shoreline

13. spit = curved extension
• May grow
across a bay
(baymouth bar)
• May link an
island to the
main land
(tombolo)

14. TIDES
Moon/
• Daily changes in sea levels Sun
• Tides rise (FLOOD) to produce
a HIGH TIDE
• And fall (EBB) (LOW TIDE)
• Produced by the gravitational
pull that the Sun and Moon exert
on the Earth’s surface (including
the oceans)

15. This side is pulled towards the
Sun and/or Moon by
gravitational attraction
This side bulges out because
of inertia
Therefore, there are two high tides on Earth at
any one time

16. Every 24 hours 50 minutes any point on the
Earth rotates through two bulges
Each location experiences 2 high (FLOOD)
tides and 2 low (EBB) tides

17. Types of Coastline
Submergence and emergence changes
coastlines
Pocket beaches

18. Emergent coast
• Uplifted land surface
• Coastal landforms are found above present sea level
a wave-cut
platform when
elevated -
uplifted marine
terrace

19. Submergent coast
• Rise in sea level
• Submergent coast
• Landforms under water
• A ria coastline is an example of submergence

20. Submergence Shorlines
• Ria coast - shorline
valleys eroded by rivers
are submerged
– has many offshore islands
– exposure to waves
erodes islands and
headlands
• Fiord coast - shoreline
valleys created by
glaciers are submerged
– valleys are deep and
straight
– because of the depth,
there are few beaches

21. Barrier Island Coasts
• Occur on low lying coasts
with gentle gradients
• BARRIER ISLANDS - low
ridges of sand built by waves
– behind the islands are lagoons
– shallow water with tidal
deposits
• TIDAL INLETS - gaps
between the islands

22. Delta and Volcano Coasts
• DELTA - deposit by rivers entering the sea
• Water slows down and spreads out as it
enters
• Channel divides and subdivides to create
DISTRIBUTARIES
• Volcano coasts develop in volcanic
deposits
• Low cliffs form in fresh lava

23. Coral reefs
• Corals build up
calcium
deposits to
produce reefs
• To grow, corals
need:
– Clear, warm,
shallow water
– Wave action Corbis Digital Stock

24. 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)

25. AEOLIAN (Eolian) LANDSCAPES
Wind erosion, transport and deposition
Occurs in dry regions, with little vegetation such as
deserts and coastal landscapes

26. 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

27. DEFLATION HOLLOWS
Removal of fine particles by wind leaves
hollows behind (DEFLATION
HOLLOWS)
Also leaves a surface of closely packed
stones (DESERT PAVEMENT)

28. 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

29. 1.) SURFACE CREEP
- material is rolled along the surface
- accounts for 20% of wind transport

30. 2.) SALTATION
- The asymmetrical bouncing of sand
grains
- Accounts for 80% of wind transport
- Cause of shifting sand dunes

31. Aggradational land forms
SAND SEAS (ERGS)
= only 25% of the world's deserts
surface may be covered in RIPPLES

32. 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

33. The formation of
dunes depends on:
- amount of sand
- speed and
direction of wind
- occurrence of
vegetation
Corbis Digital Stock

34. wind direction
BACKSLOPE SLIPFACE
crest
angle of
of sand repose
ent
m ov em

35. TYPES OF SAND DUNE
1.) BARCHAN
- most common type
- crescent-shaped
backslope
slip face
Wind direction

36. 2.) PARABOLIC DUNES
- crescent-shaped but with the concave side
on the windward side
- usually elongated
- may develop in associated with deflation
hollows
Wind direction

37. 3.) TRANSVERSE DUNES
• low sand ridge at right angles to the wind
direction
• may form because of large amounts of sand
wind

38. 4.) LONGITUDINAL DUNES
• low sand ridges parallel to the wind direction
• may form because of a limited amount of sand
• also known as seif dunes
wind

39. LOESS
• Finely
textured
sediment
wind-blown
long
distances
• Wind-blown
glacial debris
formed large
deposits

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