1. Notes – Chapter 12 Ocean Waters and the Ocean Floor

2. The Vast World Ocean Area of Continents and Oceans
Seventy one percent (71%) of the globe is covered with oceans or seas.
Continents and islands compose the remaining twenty nine percent (29 %).

3. The Vast World Ocean Distribution of Continents and Oceans
Northern Hemisphere - 61% Water / 39% Land
Southern Hemisphere – 81% Water / 19% Land

4. The Vast World Ocean Volume of Continents vs Oceans
Volume of land above sea level (continents) is 1/18 the volume of the ocean.

5. The Vast World Ocean Height vs Depth
Average elevation of continents is 840 meters above sea level.
Average depth of oceans is 3800 meters below sea level.
If the Earth were perfectly smooth and spherical the oceans would cover it to a uniform depth of 2000 meters.

6. The Vast World Ocean Comparison of Major Oceans Pacific Ocean
Largest ocean, equal to the Atlantic and Indian together
Contains > half the world’s ocean water
Greatest average depth, 3940 meters

7. The Vast World Ocean Comparison of Major Oceans Atlantic Ocean
Greatest north-south extension
Shallowest, average depth 3310 meters

8. The Vast World Ocean Comparison of Major Oceans Indian Ocean
Smallest of the three major oceans
Mostly located in the southern hemisphere

9. Composition of Seawater
Seawater – complex solution of salts, consisting of about 3.5 % dissolved mineral substances (normally range between 3.3% and 3.7% in the open ocean).
If all water evaporated a layer of salt 60 meters thick would cover the ocean floor.

10. Composition of Seawater
Salinity – proportion of dissolves salts to pure water, expressed in either parts-per-thousand or percentages (%)

12. Composition of Seawater
Component Elements – Mostly sodium chloride (NaCl) but seawater contains more than 70 of Earth’s 92 naturally occurring elements.

14. Composition of Seawater
Variation in Salinity – based on differences in the percentage of water, not differences in types of salts.
High Salinities – found where evaporation is high (sub tropics) Ex. Persian Gulf and the Red Sea – exceeds 4.2%
Low Salinities – found where heavy precipitation dilutes ocean water (near the mid latitudes and equator) Ex. Baltic Sea – less than 1.0%

16. Composition of Seawater
Source of Salts –
Chemical Weathering of Rocks
Volcanic Eruptions

17. Resources From Seawater
Salt
Fresh Water
Desalinization
Gold

19. The Ocean’s Layered Structure
Determined by differences in temperature and salinity at different depths

20. The Ocean’s Layered Structure
Shallow Surface Mixed Zone
Warmest
Higher Salinity

21. The Ocean’s Layered Structure
Transition Zone (Thermocline/Halocline)
Greatest Drop in Temperature

22. The Ocean’s Layered Structure
Deep Zone
Coldest – Temperatures below 4° C
Lowest Salinity

24. Earth Beneath the Sea H.M.S. Challenger (1872-1876)
Trip went through every ocean except the Arctic
Sampled depths using a weighted line

25. Earth Beneath the Sea Echo Sounder (1920s)
Transmitted sound toward the ocean bottom and a receiver measured how long it took for the sound waves to return.
Had to know how fast sound travels in water (1500meters or 5000 feet per second)

26. Earth Beneath the Sea

27. Continental Margins
Includes continental shelf, continental slope and continental rise.

28. Continental Margin

29. Continental Margin

30. Continental Margins
Continental Shelf –gently sloping submerged surface extending from the shoreline toward the deep-ocean basin at the shelf break.
Flooded extension of continents, it can vary in size.
Can be a source of important minerals, petroleum, etc.

31. Continental Margins Continental Slope and Rise
Continental Slope – edge of the continental shelf leading into deep waters and is the true edge of the continent.
Continental Rise – gradual incline further seaward from the continental slope, sometimes nonexistent where the slope descends into a submarine canyon.

32. Submarine Canyons and Turbidity Currents
Extend to depths as great as 3 kilometers
Created by processes operating below the Earth’s surface as well as turbidity currents

33. Submarine Canyons

34. Submarine Canyons and Turbidity Currents
downslope movement of dense sediment laden waters
eroding and accumulating more sediment as it moves toward the ocean basin.

35. The Ocean Basin Floor
Comprises 30% of Earth’s surface.

36. The Ocean Basin Floor
Deep Ocean Trenches – long narrow troughs that are the deepest part of the ocean
Challenger Deep in the Marianna Trench is more than
11,000 meters deep
Sites where crustal plates are plunging back into the mantle

37. The Ocean Basin Floor Abyssal Plains – flattest places on Earth
Turbidity currents deposit their sediments here

38. The Ocean Basin Floor
Seamounts – isolated volcanic peaks, maybe be islands or submerged
Some form from hotspots, some near plate boundaries

39. Mid Ocean Ridges
Form an almost continuous underwater mountain chain through all major oceans
Comprise 20% of Earth’s surface

40. Mid Ocean Ridges
Rift zone – region where magma from the asthenosphere moves upward to create new crust

41. Coral Reefs and Atolls Coral Reefs
Constructed from the skeletal remains and secretions of corals and certain algae, built up over time
Thrive in warm waters and rarely occur elsewhere, they require clear, sunlit waters with very little variation in temperature

42. Coral Reefs and Atolls Atolls
Remains of coral reefs surround volcanic islands that have since sank back into the ocean

43. Seafloor Sediments Terrigenous Sediment – “derived from land”
Weathered continental rock transported to the ocean
Biogenous Sediment –“derived from organisms”
Shells or skeletons of marine animals and plants
Hydrogenous Sediment – “derived from water”
Minerals that crystallize directly from seawater

44. Marianas Trench