1. The Dynamic Ocean
Ch. 16

2. Currents move water from place to place

3. There are 2 kinds of currents…

4. Surface currents: move on or near surface of ocean
First kind of current:
Surface currents: move on or near surface of ocean
Most are caused by wind
Friction between wind blown air and the water surface causes the water to move
Controlled by wind belts, earth’s rotational effect and location of continents

10. Surface Currents

11. What direction do most currents NORTH of the equator move?

12. CLOCKWISE!

13. What direction do most currents SOUTH of the equator move?

14. COUNTERCLOCKWISE!

15. Western side of ocean has warm currents traveling from equator
Eastern side of ocean has cool currents moving toward equator

16. Examples of warm water currents:
Gulf Stream
Brazil
Kuroshio

17. Examples of cold water currents:
California current
Canary current
Labrador current

18. Second kind of current:
2. Deep density currents: cold, dense currents that flow very slowly beneath surface of ocean
Occurs when denser seawater moves towards an area of less dense seawater

19. In the deep ocean, denser water around the Poles sinks and travels along the ocean floor toward the equator.
At the same time, less dense water at the equator rises and moves towards the poles along the surface.
These two events form a continuous cycle that circulate ocean water.

20. Wave Generating forces
WIND
TIDES
Sometimes Earthquakes

21. Features of a wave
CREST
WAVE HEIGHT
TROUGH
WAVELENGTH

22. Wavelength
Distance from one crest to another

23. Wave Height
Difference between crest to trough

25. Period:
The time it takes one wavelength to pass a given point

26. Speed= wavelength
period

27. Test your knowledge…
What is the speed of a wave 24 meters long with a period of 4 seconds?

28. Speed = 24 meters= 6 meters/sec

29. Observe an animation of wave motion.

30. Swells Group of long, rolling waves all about the same size
Come at regular intervals

32. Height of wind-formed waves depends on 3 things…
Length of time the wind blows
Speed of wind
FETCH: length of open water over which the wind blows in a single direction

34. As waves approach shore, the water is so shallow that they touch bottom. This happens at a depth of one-half the wavelength. As the wave scrapes bottom, the lower part of wave slows down and upper par moves ahead. The crest falls over and breaks onto the beach.

36. Observe waves as they break on the shore.

39. MAVERICKS

41. Waves and the shore:
Breakers – foamy mass of water that washes onto shore
Undertow
Long shore current
Tsunamis
Rip current – strong surface currents that flow away from the beach; hazard to swimmers

42. TSUNAMIS

43. TSUNAMIS “Tidal waves” More appropriately called Seismic sea waves
Long wavelength
Long periods
Low height – until they reach land!

44. http://www. geophys. washington

45. Rip Currents

47. What To Do if Caught in a Rip Current What should you do if you are caught in a rip current? First, REMAIN CALM! Signal to someone on the beach, a lifeguard or a friend, that you need help. If you are a strong swimmer, try to swim parallel to the beach until you are out of the rip current. Then swim toward the shore. Never try to swim back to shore directly against the Rip current, as this can exhaust and drown even the strongest swimmer. For the less confident swimmers, wade sideways parallel to the beach until you are out of the Rip’s pull, then swim back to shore.

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

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

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

52. 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

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

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

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

58. tombolo: deposit that connects an offshore island to the mainland

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

61. Observe an animation showing the formation of an arch.

62. Evolution of Shoreline Features
Makes no sense without caption in book

65. Examine an example of wave erosion.

66. 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

67. 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

68. A close-up view of ordinary sand

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

70. Hawaii
black/gray sand
erosion from dark volcanic rock

71. 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

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

74. 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

76. LONGSHORE CURRENT
BACKWASH
SWASH
direction of sand drift
BEACH

78. 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

82. 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

85. 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

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

91. 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

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

94. Barrier Islands
Makes no sense without caption in book

96. Stabilizing the Shore  Protective Structures  Beach Nourishment
• Groins, breakwaters, and seawalls are some structures built to protect a coast from erosion or to prevent the movement of sand along a beach.
 Beach Nourishment
• Beach nourishment is the addition of large quantities of sand to the beach system.

97. Miami Beach Before and After Beach Nourishment
Makes no sense without caption in book

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