1. Understanding Earth Chapter 20: COASTLINES AND OCEAN BASINS
Grotzinger • Jordan
Understanding Earth
Sixth Edition
Chapter 20:
COASTLINES AND
OCEAN BASINS
© 2011 by W. H. Freeman and Company

2. Coastlines and Ocean Basins
Chapter 20
Coastlines and Ocean Basins

3. About Coastlines and Ocean Basins
Coastal processes are the interaction of the climate system and the solar system.
Waves and tides are key processes at the coastline.
The ocean basin contains features like mountains, valleys, and volcanoes.

4. Lecture Outline How ocean basins differ from continents
2. Coastal processes
3. The shaping of shorelines
4. Continental margins
5. Topography of the deep sea floor
6. Ocean sedimentation

5. How Ocean Basins Differ
from Continents
● Lack of fragmentation processes
● slow chemical weathering
● Limited tectonic activity
● mid-ocean ridges and
subduction zones
● Oceans dominated by volcanism
and sedimentation

6. ● Wave motion – key to shoreline dynamics
2. Coastal Processes
● Wave motion – key to shoreline
dynamics
● Wind waves: depends on wind
speed, duration, and distance

7. Coastal Processes:
Straight Sandy Beach
Pea Island, North Carolina

8. Coastal Processes: Rocky Coastline
Mount Desert Island, Maine

9. Coastal Processes:
Wave Erosion Effects
Port Campbell, Australia

10. Coastal Processes: Reef and Beach
southern Florida

11. ● period for successive waves
2. Coastal Processes
● To describe a wave
● wavelength
● wave height
● period for successive waves

12. ● The velocity of a wave (V) ● V = L x T ● L = wavelength ● T = period
2. Coastal Processes
● The velocity of a wave (V)
● V = L x T
● L = wavelength
● T = period

13. 2. Coastal Processes:
Wave Motion Near Shore

14. 2. Coastal Processes:
Wave Motion Near Shore

15. 2. Coastal Processes:
Wave Motion Near Shore

16. 2. Coastal Processes:
Wave Motion Near Shore

17. 2. Coastal Processes:
Wave Motion Near Shore

18. ● waves break (collapse) as they approach the shore
2. Coastal Processes
● The surf zone
● nearshore area
● waves break (collapse) as
they approach the shore
● swash and backwash on shore

19. ● wave crests bend as they approach the shore
2. Coastal Processes
● Wave refraction
● wave crests bend as they
approach the shore
● waves break (collapse) as
they approach the shore
● swash and backwash on shore

20. ● Longshore currents (parallel to shore)
2. Coastal Processes
● Longshore currents (parallel to shore)
● caused by wave approach at an
angle to the shore
● zig-zag path of swash and
backwash occurs at the shore
● Rip currents (perpendicular to shore)

21. ● The tides: gravitational origin ● solar tides
2. Coastal Processes
● The tides: gravitational origin
● solar tides
● lunar tides: spring and neap

22. ● Earth-Moon-Sun alignment ● shoreline configuration
2. Coastal Processes
● The height of tides
● Earth-Moon-Sun alignment
● shoreline configuration
● tidal surges with storms

23. Bulging Water of the Tides
2. Coastal Processes:
Bulging Water of the Tides

24. 2. Coastal Processes:
Spring Tides

25. 2. Coastal Processes:
Neap Tides

26. ● Tidal currents ● flood tidal current ● ebb tidal current
2. Coastal Processes
● Tidal currents
● flood tidal current
● ebb tidal current

27. ● Hurricanes and storm surges ● cyclonic storms with winds
2. Coastal Processes
● Hurricanes and storm surges
● cyclonic storms with winds
of 260+ km/hr (160+ mi/hr)
● ahead of the storm: dome of
sea water floods coastal areas

28. Coastal
Processes:
Hurricane
Katrina,
August 2005

29. Coastal Processes: Storm Surge Effects
New Orleans, Louisiana

30. Coastal Processes: Storm Surge Effects
Hurricane Katrina – August 2005

31. Coastal Processes: Storm Surge Effects

32. ● Hurricanes and their intensity ● Saffir-Simpson scale
2. Coastal Processes
● Hurricanes and their intensity
● Saffir-Simpson scale
● counter-clockwise in northern
hemisphere

34. Coastal Processes: Hurricanes

36. Thought questions for this chapter
After a period of calm along a section of the Gulf Coast of North America, a severe storm with high tides passes over the shore and up the Mississippi Valley. Describe the state of the surf zone before the storm, during it, and after the storm has passed. What would happened to inland rivers?

37. ● foreshore (surf zone, tidal flat, and swash zone) ● offshore
3. The Shaping of Shorelines
● Structure of beaches
● backshore
● foreshore (surf zone, tidal flat,
and swash zone)
● offshore

38. 3. The Shaping of Shorelines: The Structure of Beaches

39. ● Sand budget of the beach ● incessant movement
3. The Shaping of Shorelines
● Sand budget of the beach
● incessant movement
● input and output (erosion and
sedimentation)
● changing conditions lead to
growth or shrinkage

41. ● Shoreline erosion and deposition ● uplift / subsidence
3. The Shaping of Shorelines
● Shoreline erosion and deposition
● uplift / subsidence
● nature of rocks or sediments
● changes in sea level
● average storm wave heights
● heights of tides

42. ● Erosional coastal forms ● sea cliffs and wave-cut terraces
3. The Shaping of Shorelines
● Erosional coastal forms
● sea cliffs and wave-cut terraces
● Depositional coastal forms
● barrier islands and spits

43. Shorelines: Four Wave-Cut Terraces
California

44. Shorelines: Sand Spit and Barrier Islands
Cape Cod, Massachusetts

46. ● Sea-level change due to warming ● melting of ice caps
3. The Shaping of Shorelines
● Sea-level change due to warming
● melting of ice caps
● expansion of water in oceans
● Effects on beaches: net erosion and
loss of the beach

47. Thought questions for this chapter
Why would you want to know the timing of high tide if you wanted to observe a wave-cut terrace?
In a 100-year period, the southern tip of a long, narrow, north-south beach has become extended by about 200 m to the south by natural processes. What shoreline processes could have caused this extension?

48. Thought questions for this chapter
You are studying a sequence of sedimentary rocks and discover that the beds near the base are shallow marine sandstones and mudstones. Above these beds is an unconformity, overlying which are nonmarine sandstones. Above this group of beds is another unconformity; overlying it are marine beds similar to those at the base. What could account for this sequence?

49. ● Types of continental margin ● passive ● active
4. Continental Margins
● Types of continental margin
● passive
● active
● Components of continental margins
● shorelines
● shelves, slopes, and rises

50. 4. Continental Margins: Passive
Submarine canyons
Deep-sea fan
Coastal plain
Abyssal plain
Continental shelf
Continental slope
Continental
crust
Oceanic crust
Continental rise
Mantle

51. Active (Marianas Type)
4. Continental Margins:
Active (Marianas Type)
Island arc
Forearc basin
Trench
Accretionary
wedge

52. 4. Continental Margins: Active (Andean Type) Continental volcanic belt
Offshore
trench
Continental crust
Oceanic crust
Mantle
Accretionary
wedge

54. ● low sloping offshore area ● economically important
4. Continental Margins
● Continental shelves
● low sloping offshore area
● economically important
● Continental slope and rise
● canyons and submarine fans
● turbidity flows of sediment

56. Continental Margins: Sand Flow
in Canyon
California

57. Continental Margins: Submarine Canyons
SHELF
SLOPE
RISE
offshore New England

58. ● How we know about the deep ● Deep Sea Drilling Project
5. Topography of the Deep Sea Floor
● How we know about the deep
● Deep Sea Drilling Project
● Ocean Drilling Program
● ship-towed instruments
● deep-diving submarines
● satellite charting of seafloor

59. 5. Topography of the Deep Sea Floor

60. 5. Topography of the Deep Sea Floor

61. ● volcanic tracks of hot spots ● deep sea trenches ● island arcs
5. Topography of the Deep Sea Floor
● Important features
● mid-ocean ridges
● volcanic tracks of hot spots
● deep sea trenches
● island arcs
● continental margins

63. ● continental slope and rise ● submarine canyons
5. Topography of the Deep Sea Floor
● Oceanic profiles
● continental shelf
● continental slope and rise
● submarine canyons
● abyssal hills and plains
● seamounts, plateaus, and island
chains
● mid-ocean ridges

64. 5. Topography of the Deep Sea Floor: The Atlantic Ocean Profile

65. The Deep Ocean:
The Atlantic
Mid-Ocean
Ridge,
Southwest
of the
Azores

66. 5. Topography of the Deep Sea Floor: The Pacific Ocean Profile

67. Thought questions for this chapter
What are the chief differences between the Atlantic and Pacific oceans with regard to topography, tectonics, volcanism, and other seafloor processes?
There is very little sediment on the floor of the central valley of the Mid-Atlantic Ridge. Why is this so?
How might plate tectonics account for the contrast between the broad continental shelf off the eastern coast of North America and the narrow, almost nonexistent shelf off the western coast?

68. Thought questions for this chapter
A major corporation hires you to determine whether New York City’s garbage can be dumped at sea within 100 km offshore. What kinds of places would you explore, and what are your concerns?

69. ● Continental shelf sedimentation ● clastics from land ● biochemical
6. Ocean Sedimentation
● Continental shelf sedimentation
● clastics from land
● biochemical
● Deep-sea sedimentation
● pelagic sediments and
foraminiferal oozes
● windblown silt and clay
● siliceous oozes (silica plankton)

70. Oceanic
Sediments:
Ooze
Made of
Planktonic
Organisms

71. Chemical Weathering and Depth
6. Ocean Sedimentation:
Chemical Weathering and Depth

72. Thought questions for this chapter
A plateau rising from the deep-sea floor to within 2000 m of the surface is mantled with foraminiferal ooze, whereas the deep seafloor below the plateau, about 5000 m deep, is covered with reddish brown clay. How can you account for this difference?

73. Key terms and concepts Abyssal plain Active margin Barrier island
Abyssal hill
Abyssal plain
Active margin
Barrier island
Beach
Carbonate compensation depth
Continental margin
Continental rise
Continental shelf
Continental slope
Foraminiferal ooze
Guyot
Hurricane
Longshore current
Passive margin

74. Key terms and concepts Seamount Shoreline Siliceous ooze Spit
Pelagic sediment
Seamount
Shoreline
Siliceous ooze
Spit
Storm surge
Tidal flat
Tide
Turbidity current
Wave-cut terrace