1. Oceanography

2. The Oceans

3. Oceanography Oceanography is the scientific study of Earth’s Oceans
Oceanographers study:
Chemical composition
Temperature
Movement of ocean water
Seafloor sediments
Topography
Marine Life

4. Earth’s Water Ocean’s contain 97% of water found on Earth
3% is located in frozen ice caps(Greenland, Antarctica)
Sea level has risen and fallen due to warming and cooling of the Earth
Tectonic Processes

5. Earth’s Oceans Earth is known as the “Blue Planet”
71% of the surface is covered by water
Average Depth is 3800 meters
Most landmasses are in the Northern Hemisphere
81% of the Southern Hemisphere is water

6. Oceans and Seas Oceans make up around 70% of the Earth’s surface
Divided into 4 Oceans:
Pacific-Largest
Atlantic-Between the Americas and Europe and Africa
Indian-3rd largest between Africa, Asia and Australia
Arctic-North of the Arctic Circle

8. Oceans and Seas The Arctic and Antarctic areas are covered by sea ice
Ice is less dense than water therefore ice crystals form at the surface
Parts break up in the summer

9. Oceans and Seas
Seas are parts of the ocean that are partially landlocked
Black Sea
Mediterranean Sea
Caribbean Sea
Bering Sea
Seas that are completely landlocked have a different composition(More salt water)
Caspian Sea
Aral Sea

10. Studying The Ocean The Challenger-Late 1800’s, British research ship
Investigated ocean currents, water temperature, sediments, topography
Used nets, dredges and other tools
Meteor- German ship in the 1920’s
Used sonar, first to map the Mid-Atlantic Ridge

11. Ocean Origin The Earth is believed to be 4.6 Billion years old
The Ocean’s are thought to be about that old
Ancient lava flows suggest this

12. Formation of the oceans
One hypothesis suggests that water was released from Earth’s interior by volcanism(out gassing)
As the Earth cooled this water vapor condensed and filled the oceans

13. Formation of the Oceans
The second hypothesis says that the water came from comets
The impact of comets releases water

14. Chemical Properties of Seawater

15. Properties of Seawater
Seawater is a solution of salts dissolved in water
Salinity is the concentration of all salts in seawater
Measured in grams of salt per kilogram of water or ppt
The average salinity is about 35 ppt
Seawater is a solution of salts dissolved in water
Salinity is the concentration of all salts in seawater
Measured in grams of salt per kilogram of water or ppt
The average salinity is about 35 ppt

16. Properties of Seawater
Most of the salt is NaCl which splits about in solution
Other ions: Sulfate, Magnesium, Calcium, Potassium, Bicarbonate

17. Variations in Salinity
The highest salinity is found in subtropical regions(20-30 latitudes)
The rate of evaporation exceeds the rate of precipitation
Polar regions have lower salinities

18. Variations in Salinity
Higher salinities are found in enclosed seas near deserts such as the Mediterranean Sea, Red Sea
The Baltic Sea receives fresh water from rivers, lower salinity
Estuaries are partly enclosed bodies of water at the mouths of rivers. Very low salinities(2-10 ppt)

19. Addition of Salt
The salinity of the oceans has remained fairly consistent over time
Volcanoes release chlorine and sulfur dioxide which dissolve in water
Weathering of continental rocks generates other ions in seawater

20. Removal of Salt
When water evaporates ions stay behind and form minerals
When organisms die ions in their shells, bones and death accumulate on the ocean floor

21. Density Pure water has a density of 1 g/ml
Seawater ranges from g/ml
This is due to variations in salinity and temperature
Density increases with increasing salinity.
Density decreases with increasing temperature
The salinity can alter the freezing point (-2 C)

22. Light Absorption Water absorbs light. Intensity decreases with depth
The absorption of different wavelengths varies as well
Marine animals may appear red near the surface but look black at a depth of 10 meters

23. Temperature
The surface of the ocean waters 15 degrees C(Is warmer near the equator)
In the Polar regions the water is cold from the surface to the seafloor
After about 100 m of ocean to about 1000 m the temperature drops from about 22 C to about 4 C

24. Temperature
The zone of rapidly decreasing of temperature with depth is called the thermocline
After the thermocline the temperature is uniform at roughly 4 degrees Celsius
Caused by differences in density

25. Water Masses Cold, salty water comes from the Earth’s poles
Sea ice forms  Salt ions are left behind  Water underneath sea ice is dense Sinks
The cold, salty water then migrates towards the equator

26. Movement of Ocean Water

27. Movement of Ocean Water
Oceans are always in constant movement caused by:
Variations in temperature
Variations in Density
Winds blowing across the water’s surface
Gravitational pull of the Moon and the Sun

28. Density Currents
The low temperatures of water at Earth’s poles are responsible for the movement of seawater
Salts accumulate beneath the ice which increasing the density of the seawater
The dense seawater sinks and moves toward the equator. This is called a density current

29. Upwelling
Upwelling is the process where cold water from the bottom of the ocean moves toward the surface
Occurs near continents.
Winds push water away from the land which is replaced by deeper water which rises
Upwelling water is rich in nutrients which supports marine life

30. Surface Currents
Surface currents are formed by Earth’s global wind systems
In the tropics trade winds blow from east to west, water moves in the same direction
Mid latitudes-Prevailing westerlies move from west to east
Polar Regions-Winds move from east to west

31. Surface Currents
Gyres are large circular current systems that flow from north to south
The Coriolis effect influences this
5 major gyres:
2 in the Pacific Ocean
2 in the Atlantic Ocean
1 in the Indian Ocean

33. Surface Currents
When a current encounters a landmass the water is deflected away from the equator
As the warm current moves North it cools and turns eastward
Gulf Stream-Flows along the east coast of North America

34. Waves
A wave is a rhythmic movement that carries energy through space or matter
Waves carry small amounts of water

35. Waves Crest-Highest point of a wave Trough-Lowest point of a wave
Wave Height-Distance between the crest and trough
Wavelength-The distance between two crests or troughs
Factors influencing wave height:
Wind Speed
Wind Duration
Fetch

37. Waves Waves lose energy when they reach shallow water due to friction
As they slow they become higher and steeper
Breakers are collapsing waves

38. Tides Sea level-Average height of the ocean’s surface
Tides-Periodic rise and fall of ocean waters caused by the gravitational attraction of the Moon and Sun

39. Tides One full tidal cycle takes about 24 Hours 50 Minutes.
This is due to the Moon rotating around the Earth
Spring Tides-When the Moon is full or new. High tides are higher than usual, low tides are lower than usual
Neap Tides-The Earth, Moon and Sun form a right angle. Lower tidal range

40. Shoreline Features

41. Shorelines
Shorelines are shaped by waves, tides and currents by erosion and deposition
Ocean floor is shaped by tectonic processes

42. Erosion
Wave Refraction is the bending of a wave when it reaches shallow water
This is caused by wave speed and water depth
A wave will reach a headland first and will bend towards the headland

43. Erosion
Most of the energy is concentrated on headlands, therefore they undergo erosion
This forms a wave cut platform at the base of a steep cliff

44. Deposition
Coastal landforms are formed by sediment from eroded land that are carried to the oceans by rivers
When waves and currents slow down these sediments settle out and build coastal landforms

45. Beaches
Beaches
A beach is a sloping band of loose sediment at the edge of an ocean
The size of the sediments depends on the energy of the wave that deposited it
A beach is a sloping band of loose sediment at the edge of an ocean
The size of the sediments depends on the energy of the wave that deposited it

46. Longshore Current
Sediment is deposited in areas where the current slows
Sandbars often form and run parallel to most beaches
Result from waves breaking and dumping sediment

47. Longshore Current
A longshore current is when a water approaches the shore at an angle
Prevailing winds and wave patterns influence which direction it will flow
Longshore currents causes and is wash up and down the beach in a zigzag pattern

48. Longshore Current
Gaps in the sandbars allow water to return to the ocean. This forms a rip current
Barrier Islands form when sandbars form at low tide and winds pile up sand

49. Barrier Island
Spit-Forms when longshore currents slow due to increased water depth
Baymouth-A spit that has grown across the mouth of a bay

50. Spit, Baymouth Bar

51. Artificial Protective Structures
Jetties-Walls of concrete or boulders that extend into the ocean on either side of the entrance to a harbor
Groins-Similar structures to jetties that trap sand on one side and not the other

53. Artificial Protective Structures
Seawall-An embankment built along the shore to protect the land from powerful waves
Erosion increases because waves are bounced back with most of their original energy

54. Changes in Sea Level Sea level has fluctuated over time
Rises in sea level after often attributed to melting glaciers
If the polar ice sheets melted sea level would rise about 70 meters
Tectonic forces can cause a change in sea level

55. Mapping The Seafloor

56. Sonar
Sonar-Emits sound pulses that the detect the depths of the ocean floor
Side Scan Sonar-Sound pulses are directed toward the seafloor at an angle.
Topographic features can then be mapped

57. Continental Margin
The continental margin is an area of continental crust that lies below sea level. Continental crust is less dense than oceanic crust

58. Continental Shelf
Continental Shelf is the portion of the continental margin that lies closest to land
Average width is about 60 km
Most of this was exposed during the last ice age

59. Continental Shelf
The continental slope is where the ocean floor drops steeply below the continental shelf
Continental Rise forms when sediments carried down the continental slope settle at its base

60. Ocean Basins
Ocean basins are areas of the seafloor that are above the oceanic crust

61. Ocean Basins Abyssal Plains are smooth parts of the ocean basins
Sohm Abyssal Plain
Hatteras Abyssal Plain
Abyssal Plains sediment has been deposited over millions of years

62. Ocean Basins Deep Sea Trenches-Deep depressions in the ocean basins
May stretch for thousands of kilometers
Mariana Trench
These are sites where tectonic plates converge

63. Ocean Basins
Mid Ocean Ridges-Chain of mountains that is broken into segments by numerous cracks(fracture zones)
May emerge from the ocean’s surface as volcanic islands
Form when magma rises along divergent plate boundaries
Mid-Atlantic Ridge

65. Hydrothermal Vents
Hydrothermal Vents are rifts in mid ocean ridges that contain springs of hot water
Seawater seeps into cracks and is warmed by the magma from the mantle
Black Smokers-Eject thick, smoke like plumes of water that can reach 350 degrees Celsius

66. Ocean Basins
Seamounts are submerged mountains that are most likely extinct volcanoes
Tablemounts (guyots) are submerged mountains with flat tops
The lack of erosional processes cause these features to last forever