1. Oceanography Chapter 10

2. Oceanography Oceanography - is the study of Earth’s oceans.
A science that draws on the methods and knowledge of geology, chemistry, physics, and biology to study all aspects of the ocean
Oceanographers may specialize in the study of the oceans’ depths, coral reefs, or the geography of the ocean floor.

3. Ocean Basins Pacific Ocean – Largest and Deepest
Atlantic – half the size of the pacific
Indian – half the size of the Atlantic but similar in depth

4. Ocean Properties Ch 10-3
Levels of salinity - can differ from place to place - precipitation, rivers, and melting glaciers lowers salinity - evaporation raises salinity - varies more at the surface than in deep ocean water
Temperature layers - surface (warmest, m deep, temperature varies) - thermocline (temperature drops sharply with depth) - deep (coldest, below 5 °C)

5. Desalination
Fresh water is a valuable natural resource that is in short supply and often depends on precipitation.
Minerals and salts in the ocean water must be removed before being drinkable.
Desalination plants remove these minerals and salts a number of ways - heating until evaporation occurs and leaves the deposits behind, then the vapor is condensed to form fresh water - freezing (frozen ocean water is free of salts), the ice is then cleaned and melted

6. Oceanic Landforms
Chapter 10-8

7. Ocean Features
Continental margin: continental shelf and continental slope.
Ocean floor: plains, mountain ranges, (mid-ocean ridges), and trenches.
Seamounts (ex. Hawaiian islands) and guyots.

8. Continental Shelf
The gently sloping submerged surface extending from the shoreline
Some continental shelves can extend as far as kilometers others are almost nonexistent
Which ocean has a larger continental shelf Pacific or Atlantic?

9. Continental Shelf Atlantic
Continental shelves important for economic purposes
Contain mineral deposits, large reservoirs of oil and natural gas.
Important for fishing grounds

10. Continental Slope
The boundary between the continental crust and oceanic crust

11. Ocean Basin Floor Deep-Ocean Trenches
Long, narrow creases in the ocean floor that form the deepest parts of the ocean
Most trenches are located along the margins of the Pacific Ocean
Many are as deep as 10,000 meters
Mariana Trench deepest – 11,022 m
Deeper than Mt. Everest is high (8,848 m)

12. Ocean Basin Floor Deep-ocean Trenches
Form at the site of plate convergence
One plate sliding underneath another plate and plunges back into the mantle
The large number of trenches and volcanic activity along the Pacific Ocean give the region its nickname the Ring of Fire

13. Trenches

14. Ocean Basin Floor Abyssal Plains Deep, extremely flat features
Most level places on Earth
Thick accumulations of fine sediments, deposited by currents or suspended sediments settling out
Atlantic ocean has the most extensive abyssal plain because it has very few trenches

15. Abyssal Plains

16. Ocean Basin Floor Seamounts Submerged volcanic peaks
Volcanoes that have not reached the ocean surface
Form at volcanic hot spots
Hawaii
Once underwater volcanoes reach the surface they form islands

17. Ocean-Basin Floor Guyots
Over time volcanic islands are eroded and sink below the ocean surface again
Once-active, now-submerged volcanoes are called guyots
This process takes millions of years

18. Mid-Ocean Ridges Found near the center of most ocean basins
Underwater mountains that have developed on newly formed oceanic crust
Longest topographic feature on Earth
70,000 kilometers in length

19. Mid-Ocean Ridges Seafloor Spreading Lots of volcanic activity
Divergent plate boundary
Two plates are moving apart
New ocean floor is formed at the mid-ocean ridges as magma rises between the diverging plates and cools

20. Seafloor Sediments
Chapter 10-7

21. Seafloor Sediments Most of the ocean floor is covered with sediment
Deposited by currents
Slowly settled onto the seafloor from above
Coarser sediments, like sand, cover the continental shelf
Finer sediments, like silt and clay, cover the deep ocean floor

22. Types of Seafloor Sediments
Ooze
Biological in origin
Consist of shells and skeletons of marine animals (usually microscopic) and algae
Produced from carbonate shells of organisms such as diatoms
Single celled algae
Shells made out of silica
Consistency thick like mud
Do not accumulate in deeper areas of ocean basins

23. Types of Seafloor Sediments
Nodules
Consist of minerals that crystallize directly from ocean water through chemical reactions
Made up of mostly manganese, nickel, and iron compounds
Small amounts of copper, lead, zinc, and silver

25. Coral Reefs
Then currents, waves, and tides together. Exploration of the ocean

26. Energy Resources
Oil and gas are the main energy products currently being obtained from the ocean floor
Ancient remains of microscopic organisms are the source of today's deposits of oil and natural gas
The organisms were buried within the marine sediments before they had a chance to decompose
After millions of years of being exposed to heat from Earth's interior and pressure from over laying rock the remains are transformed into oil and gas

27. Energy Resources
30% of the worlds oil production comes from offshore drilling
This has greatly increased from only trace amounts in the 1930s
This increase is due to updates in technologies
Offshore reserves
Persian Gulf, Gulf of Mexico, off the coast of southern California, North Sea, East Indies and many others

28. Energy Resources
Could there be a problem with offshore drilling?

29. Gas Hydrates
Are compact chemical structures made of water and natural gas
Most common gas hydrate is methane
Form under the ocean floor at depths below 525 meters
Why do you think we do not mine for gas hydrates?

30. Other Seafloor Resources
Sand and gravel, evaporative salts, and manganese nodules

31. Sand and Gravel Sand and gravel are mined by offshore barges
Used for landfill, to fill in recreational beaches, and to make concrete
Great economic value only second to the off shore oil industry
Some sands are then mined for diamonds, tin, platinum, and titanium

32. Manganese Nodules
Hard lumps of manganese and other metals that precipitate around a smaller object
With current technology mining the deep- ocean floor for manganese nodules is possible but not profitable

33. Evaporative Salts
When seawater evaporates the salt increase in concentration until they can no longer remain dissolved
The salts precipitate out of solution and form salt deposits
Used for table salt, de ice roads, and dying fabric