1. Erosion by Wind and Waves
Ch. 16

2. Wind Deposition
when the wind stops, it drops its load

3. Dunes: mounds of wind blown sand
form where soil is dry and unprotected and the wind is strong

4. How dunes form: when a barrier slows the speed of the wind, it causes sand to accumulate on the sheltered side, sand accumulates on exposed side, and eventually buries the barrier

5. Wind causes saltation, or jumping grains, on the windward side of sand dunes

6. slipface
windward
crest

7. Types of Dunes
barchan dune: crescent shaped, open side faces away from wind, common, found in deserts

10. parabolic dune: crescent-shaped, open sided faces into the wind

12. transverse dune: series of ridges of sand in long, wave-like patterns- form at a right angle to the wind

14. longitudinal dune: ridges of sand in long, wave-like patterns- lie parallel to the wind direction

16. This Landsat image reveals sand dunes advancing on Nouakchott, the capital of Mauritania.

17. Alien dunes. NASA's Mars Global Surveyor photographed these sand dunes on Mars

18. Shoreline erosion is caused by:
waves weathering rock
chemical weathering
storms

19. Shoreline Features
sea stack: offshore, isolated columns of rock which was once connected to the headland

21. sea cliff: high, nearly vertical,steep structure that forms where waves strike directly against the rock

22. terraces: a nearly level platform that is found at the base of a sea cliff
wave-cut: formed when a sea cliff is worn back
wave-built: forms when eroded material is deposited

24. sea cave: large holes found in a sea cliff

25. spit: long, narrow deposit of sand connected at one end to the shore

27. The formation of a spit by sand movement in response to longshore currents.

28. tombolo: deposits that connect an offshore island to the mainland

30. sea arch: enlarged sea cave, produced when waves cut through the headland

33. beach: a deposit of sand or rock fragments along an ocean shore
form where amount of fragments moving toward shore is greater than amount moving away

34. size and kinds of materials found on beaches vary widely
Boulders
more than 256mm
Cobbles
64 to 256 mm
Gravel
2 to 64 mm
Sand
.06 to 2 mm
Silt
less than 0.06mm

35. A close-up view of ordinary sand

36. Atlantic Coast white sand with quartz and feldspar
erosion from Appalachian Mountains

37. Hawaii black/gray sand from basalt
erosion from dark volcanic igneous rock

38. each wave reaching the shore moves individual sand grains forward total action of thousands of waves moves sand a great distance sand piled up on shore producing sloping surface

39. berm: raised section at the back of the beach
results from high tides or large storm waves

41. sandbar: long ridge of sand deposited offshore
In winter, large storm waves remove sand from the beach and deposit it offshore
sandbar: long ridge of sand deposited offshore
In summer, waves return the sand to the beach

43. LONGSHORE CURRENT
BACKWASH
SWASH
direction of sand drift
BEACH

45. swash: motion of water up a beach
the direction a wave approaches the shore determines sand grain movement
swash: motion of water up a beach
backwash: water that runs back down the beach under the next wave
strong backwash is called an undertow

49. longshore current: movement of water parallel to and near the shore
transport sand in direction parallel to shore
may produce a spit or a tombolos

52. Processes that Affect Coastlines
long term rising and falling of the sea level
long term uplifting or sinking of land that borders water
wave erosion and deposition
The sea level is now rising at a average rate of about 1mm/yr

54. SUBMERGENT COASTLINES
estuary: bay where freshwater and saltwater mix
forms when sea level rises and sinks

58. EMERGENT COASTLINES
barrier islands: long, narrow offshore ridges of sand many over 100 km long
lie parallel to the shore about 3 km to 30 km offshore
lagoon: narrow region of shallow water between barrier islands and shore

59. sometimes a hazardous place to live because it is severely eroded by storms

62. coral reefs: ridge-like features made from millions of coral skeletons- form around tropical volcanic islands
fringing reef: coral reef formed around the coast of a volcanic island
barrier reef: coral reef that forms around the remnant of an island
atoll: nearly circular coral reef surrounding a shallow lagoon where a volcanic island used to be

65. PRESERVING THE COASTLINE
(two things that damage the coastline)
recreation, commercial fishing, shipping, industrial and residential development
pollution