1. O ceans and Coasts
Chapter 18

2. Outline
• Ocean exploration & oceanography
• The globes’ oceans
-Lithosphere density and ocean basins
-Global ocean landscape
• Submarine landscape
-Major zones (shelf to Abyssal plains) – reflection of tectonics
-Continental margins, submarine canyons
-Ocean water composition, temperature
• Ocean dynamics
-Currents, Coriolis effect, tides, waves
• Coastal landforms
-beaches, barrier islands, rocky coasts, tidal flats, reefs etc..
Chapter 18
Chapter 18

3. Oceans
• Humans have explored the ocean for centuries.
• Before 1800s, sea floors was unknown
• HMS Challenger (1872-1876) 1st oceanography study
• Dredged sea floor rocks
• Measured seawater, depth, currents
• Analyzed water
• Collected biota
Chapter 18

4. Oceans
• Our knowledge of oceans has expanded greatly:
• Oceanography – study of ocean water and its movement
• Marine geology – study of ocean floor rocks/seds
• Marine biology – study of ocean life
Chapter 18

5. Oceanography
• Instruments have greatly expanded our knowledge.
• Submarine exploration – Alvin (WHOI)
• Bathymetric mapping – sonar/radar
• Ocean drilling- recovers time archived below the seafloor
• Major drilling projects (DSDP, ODP, IODP)
Chapter 18

6. Oceanography
• Seismic reflection profiling.
• Sound waves pass through water and sediment
• Some waves bounce off each subsurface layer
• Travel time of reflected waves captured by geophones
• Used to make images of ocean floor geology
Chapter 18

7. Outline
• Ocean exploration & oceanography
• The globes’ oceans
-Lithosphere density and ocean basins
-Global ocean landscape
• Submarine landscape
-Major zones (shelf to Abyssal plains) – reflection of tectonics
-Continental margins, submarine canyons
-Ocean water composition, temperature
• Ocean dynamics
-Currents, Coriolis effect, tides, waves
• Coastal landforms
-beaches, barrier islands, rocky coasts, tidal flats, reefs etc..
Chapter 18
Chapter 18

8. The Global Oceans
• Ocean covers 70.8% of Earth’s surface
• Largest reservoir in hydrologic cycle
• Oceans…
• Serve as basis for life
• Regulate climate
• Cycle mass and energy
• Linked to atmosphere,
• lithosphere, biosphere
Chapter 18

9. Global Landscape
• Oceans exist because of lithosphere differences.
• Continental lithosphere
• Oceanic lithosphere
• Ocean basins collect
Chapter 18

10. Global Ocean Landscape
• The world ocean is
• Tectonic processes
• Biotic activity:
Chapter 18

11. Global Ocean Landscape
• Present configuration of tectonic plates…
• Most continental crust in
• Most oceanic crust in
Chapter 18

12. Outline
• Ocean exploration & oceanography
• The globes’ oceans
-Lithosphere density and ocean basins
-Global ocean landscape
• Submarine landscape
-Major zones (shelf to Abyssal plains) – reflection of tectonics
-Continental margins, submarine canyons
-Ocean water composition, temperature
• Ocean dynamics
-Currents, Coriolis effect, tides, waves
• Coastal landforms
-beaches, barrier islands, rocky coasts, tidal flats, reefs etc..
Chapter 18
Chapter 18

13. Undersea Landscapes
• Sea floor bathymetry
• Continental shelf –
• Continental slope –
• Abyssal plain –
Chapter 18

14. Undersea Landscapes
• Sea floor reflects
• Continental shelf –
• Continental slope –
• Abyssal plain –
Chapter 18

15. Undersea Landscapes
Continental margins:
• Passive
• Active
western SA: active
Eastern NA: passive
Chapter 18

16. Undersea Landscapes
• Submarine canyons
• Associated with
• Carved during
• Funnel sediments to
• Submarine fans grow where
Chapter 18

17. Ocean Water Composition
• Normal marine salinity, reflecting dissolved ions, is
• Dissolved ions derive from
• Ions mostly
Chapter 18

18. Ocean Water Composition
• Surface salinity can vary.
• Higher salinity 
• Lower salinity 
• Salinity becomes
Chapter 18

19. Ocean Water Temperature
• Ocean surface T varies
• Water buffers
• Water T approaches
• Ocean bottom water is
Chapter 18

20. Outline
• Ocean exploration & oceanography
• The globes’ oceans
-Lithosphere density and ocean basins
-Global ocean landscape
• Submarine landscape
-Major zones (shelf to Abyssal plains) – reflection of tectonics
-Continental margins, submarine canyons
-Ocean water composition, temperature
• Ocean dynamics
-Currents, Coriolis effect, tides, waves
• Coastal landforms
-beaches, barrier islands, rocky coasts, tidal flats, reefs etc..
Chapter 18
Chapter 18

21. Oceanic Currents
• Currents continuously
• Surface currents (upper 100 m) - due to
• Current motion creates
Chapter 18

22. The Coriolis Effect
• Earth rotation deflects
• Acts as an
• Coriolis deflection sense depends upon…
• Merry-go-round analogy:
Chapter 18

23. The Coriolis Effect
• Surface winds & currents are
• North hemisphere:
• S-moving winds/currents deflected
• N-moving winds/currents deflected
• South hemisphere.
• N-moving winds/currents deflected
• S-moving winds/currents deflected
Chapter 18

24. Vertical Oceanic Currents
• Currents also transport
• Downwelling –
• Upwelling –
• Wind perpendicular to shore
• Onshore –
• Offshore –
Downwelling Upwelling
Chapter 18

25. Vertical Oceanic Currents
• Thermohaline contrast also
• Temp – cold water
• Salinity – More saline water
• Polar water is both
• Deep ocean waters are
Chapter 18

26. Oceanic Currents
• Sinking polar water is
• This process carries
• These surface currents
• System forms a
Chapter 18

27. Tides
• Sea level rises and falls
• High tide –
• Low tide –
• Tidal reach –
• Intertidal zone
Chapter 18

28. Tides
• Caused by:
• Gravitational pull of
• Centrifugal forces from
• Orbiting moon creates strongest tidal effects.
• Sublunar bulge follows
• Smaller bulge occurs
• Bulges = ; low tides =
Chapter 18

29. Tides
• Lunar & solar tidal effects
• Positive alignment yields
• Negative alignment results in
Chapter 18

30. Waves
• Ocean waves develop via friction from wind on water.
• Gentle wind  ; gales 
• Waves move upper part
• Wave height, length, and period depend on
Chapter 18

31. Waves
• Wave anatomy:
• Crest –
• Trough –
• Wavelength –
• Depth of influence (wave base) is ½ the wavelength.
• Above wave base, water
• Below wave base, water
Chapter 18

32. Waves
• As waves approach shore,
• Friction
• Near surface, waves
• Wave
• This zone features
Chapter 18

33. Waves
• Waves that crash onto beach 
• Wave energy dissipated by
• Creates
• Water surge (swash)
• Gravity pulls
Chapter 18

34. Wave Refraction
• Irregular shoreline 
• As waves drag on bottom,
• This process, wave refraction, has consequences:
• Wave attack concentrated
• Wave attack is dissipated
• Tend to
Chapter 18

35. Longshore Currents
• Sediment is transported along shore.
• Oblique waves push
• Gravity then pulls
• Zig-zag pattern
Chapter 18

36. Rip Currents
• Develop when wave flow is
• Water piles up on beach,
• Rip current develops
• Rip currents are
• Rip currents dissipate away from
Chapter 18

37. Outline
• Ocean exploration & oceanography
• The globes’ oceans
-Lithosphere density and ocean basins
-Global ocean landscape
• Submarine landscape
-Major zones (shelf to Abyssal plains) – reflection of tectonics
-Continental margins, submarine canyons
-Ocean water composition, temperature
• Ocean dynamics
-Currents, Coriolis effect, tides, waves
• Coastal landforms
-beaches, barrier islands, rocky coasts, tidal flats, reefs etc..
Chapter 18
Chapter 18

38. Coastal Landforms
• A variety of landforms
Chapter 18

39. Beaches
• Dominated by
• Gravel beaches reflect
• Muds
• Turbulent surf
• Muds transported to
Chapter 18

40. Beaches
• Beach sediment composition reflects
• Quartz
• Carbonates
• Resistant
Chapter 18

41. Beaches
• Beaches develop distinctive
• Profiles change
• Summer –
• Winter –
Chapter 18

42. Beaches
• Distinct zones exist along a beach profile.
• Foreshore or intertidal –
• Beach face –
• Backshore –
• Beyond reach of
• Often exhibit
Chapter 18

43. Beaches
• Longshore currents move
• This process, beach
• Beach drift builds
Chapter 18

44. Beach Drift
Beach Drift
This animation illustrates the sawtooth motion that causes
sand to gradually migrate along beaches in a process called
beach drift, and shows how this can create sand spits in
places where the coastline indents landward. For more
information, see Section 18.6 Where Land Meets Sea:
Coastal Landforms starting on p. 638 and Figure 18.20 in
your textbook.
Chapter 18

45. Barrier Islands
• Barrier islands are
• Form where
• Protected backwater area called
• Common places for
• They are
Chapter 18

46. Tidal Flats
• Form in intertidal zones
• Common behind
• Thinly laminated
• Ancient tidal flat sediments
Chapter 18

47. Rocky Coasts
• Bedrock intersects
• Wave action is
• Wave energy acts
• Develop unique
Chapter 18

48. Rocky Coasts
• Wave-cut notches –
• Cliff
• Over time, cliff
• An erosional remnant of
• Often exposed at
Chapter 18

49. Rocky Coasts
• Rocky headlands are
• Refracted waves focus
• Erosion from both sides
• Collapse of the
Chapter 18

50. Wetlands
• Wetlands cover
• Develop in places protected from
• Fuel high
• Vegetation governed by
• Temperate -
• Tropical –
Chapter 18

51. Estuaries
• River valleys flooded by
• Mixed
• Modern estuaries are
• Rivers carved canyons during
• Sea-level rise
Chapter 18

52. Fjords
• Flooded
• Form spectacular
• Notable examples found in…
• Norway.
• British Columbia.
• New Zealand.
Chapter 18

53. Reefs
• Coral reefs grow in
• Large structures of
• Most biologically productive
Chapter 18

54. Reefs
• Coral reefs
• Reefs alter
• Protect
• Abundant debris is shed to adjacent environments.
Chapter 18

55. Reefs
• Coral atolls  reefs formed on
• Reef is established when
• After extinction,
• Reef can easily keep pace
• Reef continues long after
Chapter 18

56. Coastal Variability
• Plate tectonic setting governs
• Passive margin –
• Active margin –
Chapter 18

57. Coastal Variability
• Global sea-level changes effect
• Inflation/deflation of
• Glaciation/deglaciation
• Pleistocene glaciations
Chapter 18

58. Coastal Variability
• Emergent coasts experience relative sea-level
• Via uplift due to
• Via sea-level
• Emergent coasts characterized by…
• River
• Terraces representing
Chapter 18

59. Coastal Variability
• Submergent coasts experience relative sea-level
• Subsidence of
• Global sea-level
• Submergent coasts characterized by
Chapter 18

60. Coastal Variability
• Shoreline character is linked to
• Balance between
• Accretionary coasts –
• Erosional coasts –
Chapter 18

61. Coastal Variability
• Climate is a strong influence on
• Harsh weather enhances
• Calm weather favors
• Tropics –
• Temperate –
• Arctic –
Chapter 18

62. Coastal Problems
• Sea-level change.
• Sea level is
• Rate of
• People living in
Chapter 18

63. Coastal Problems
• Beach
• Storms (e.g. hurricanes)
• Human development in coastal settings
• Construction in coastal settings is
Chapter 18

64. Mitigating Coastal Problems
• Artificial barriers built to
• Groins, jetties, breakwaters
• Usually produces
• Deposition is enhanced
• BUT, erosion is accelerated
Chapter 18

65. Mitigating Coastal Problems
• Approach to combat erosion 
• Seawalls may hasten erosion.
• Wave energy is
• Erosion enhanced
• Seawalls can
Chapter 18