Notes – Chapter 12 Ocean Waters and the Ocean Floor - PowerPoint Presentation

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

2. The Vast World OceanArea of Continents and OceansSeventy 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 OceanDistribution of Continents and Oceans Northern Hemisphere - 61% Water / 39% LandSouthern Hemisphere – 81% Water / 19% Land

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

5. The Vast World OceanHeight vs DepthAverage 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 OceanComparison of Major Oceans Pacific Ocean Largest ocean, equal to the Atlantic and Indian togetherContains > half the world’s ocean waterGreatest average depth, 3940 meters

7. The Vast World OceanComparison of Major Oceans Atlantic OceanGreatest north-south extensionShallowest, average depth 3310 meters

8. The Vast World OceanComparison of Major Oceans Indian OceanSmallest of the three major oceansMostly located in the southern hemisphere

9. Composition of SeawaterSeawater – 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 SeawaterSalinity – proportion of dissolves salts to pure water, expressed in either parts-per-thousand or percentages (%)

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

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14. Composition of SeawaterVariation 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%

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16. Composition of SeawaterSource of Salts – Chemical Weathering of RocksVolcanic Eruptions

17. Resources From SeawaterSaltFresh WaterDesalinizationGold

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

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

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

22. The Ocean’s Layered StructureDeep ZoneColdest – Temperatures below 4 CLowest Salinity 

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

25. Earth Beneath the SeaEcho 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 MarginsContinental 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 MarginsContinental Slope and RiseContinental 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 CurrentsSubmarine CanyonsExtend to depths as great as 3 kilometersCreated by processes operating below the Earth’s surface as well as turbidity currents

33. Submarine Canyons

34. Submarine Canyons and Turbidity CurrentsTurbidity 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 oceanChallenger Deep in the Marianna Trench is more than 11,000 meters deepSites where crustal plates are plunging back into the mantle

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

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

39. Mid Ocean Ridges Form an almost continuous underwater mountain chain through all major oceansComprise 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 AtollsCoral ReefsConstructed from the skeletal remains and secretions of corals and certain algae, built up over timeThrive in warm waters and rarely occur elsewhere, they require clear, sunlit waters with very little variation in temperature

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

43. Seafloor SedimentsTerrigenous Sediment – “derived from land”Weathered continental rock transported to the oceanBiogenous Sediment –“derived from organisms”Shells or skeletons of marine animals and plantsHydrogenous Sediment – “derived from water”Minerals that crystallize directly from seawater

44. Marianas Trenchhttp://www.youtube.com/watch?v=KuPfn5faawE