1. Karleskint Small Turner Chapter 3 Geology of the Ocean

2. Key Concepts The world ocean has four main basins: the Atlantic, Pacific, Indian, and Arctic. Life first evolved in the ocean. The earth’s crust is composed of moving plates. New seafloor is produced at ocean ridges and old seafloor is removed at ocean trenches.

3. Key Concepts The ocean floor has topographical features similar to those found on continents. The seafloor is composed of sediments derived from living as well as nonliving sources. Latitude and longitude determinations are particularly necessary for precisely locating positions in the open sea, where there are no features at the surface.

4. World Ocean Primitive earth and formation of the ocean –early earth thought to be composed of silicon compounds, iron, magnesium oxide, and other elements –gradually, the earth heated, causing melting and separation of elements –water vapor locked within minerals worked its way to the surface, where it cooled, condensed, and formed the ocean

5. World Ocean Ocean and the origin of life –atmosphere formed by gases escaping from deep within the planet –free oxygen formed oxides, oxygen did not accumulate until evolution of modern photosynthesis –Stanley Miller’s apparatus demonstrated that simple organic compounds could have been formed under conditions present on primitive earth

8. World Ocean The ocean today –4 major ocean basins: Pacific Atlantic Indian Arctic –Pacific Ocean - largest –Arctic Ocean - smallest –Seas - smaller than ocean, essentially landlocked

11. Continental Drift Layers of the earth –Inner core: solid, iron- and nickel-rich –Outer core: liquid (same composition) –Mantle: thickest layer with greatest mass, mainly magnesium-iron silicates –Crust: thinnest and coolest, outermost –Lithosphere: crust and upper mantle –Asthenosphere: region of mantle below the crust

14. Continental Drift Moving continents –Alfred Wegener –Continents fit together like pieces of jigsaw puzzle –One supercontinent - Pangaea –Laurasia and Gondwanaland

16. Continental Drift Forces that drive continental movement –magma moves by convection currents –midocean ridges - form along cracks where magma breaks through the crust –at subduction zones, old crust sinks into the mantle where it is recycled –seafloor spreading causes continental drift

19. Continental Drift Evidence for continental drift –fit of continental boundaries –earthquakes –seafloor temperatures highest near ridges –age of crust, as determined by samples drilled from the ocean bottom, increases with distance from a ridge

23. Continental Drift Theory of plate tectonics –lithosphere is viewed as a series of rigid plates separated by earthquake belts –divergent plate boundaries: located at midocean ridges where plates move apart –convergent plate boundaries: located at trenches where plates move toward each other –faults: regions where plates move past each other (e.g. transform faults) –rift zones: where lithosphere splits

24. Continental Drift Rift (Deep Sea Vent) Communities –depend on specialized environments found at divergence zones of the ocean floor –first discovered by Robert Ballard and J.F. Grassle in 1977, in the Galápagos Rift –primary producers are chemosynthetic bacteria

25. Ocean Bottom Bathygraphic features –Geological features similar to land: mountain ranges; canyons, valleys; great expanses Continental margins –continental shelf, continental slope, and shelf break Submarine canyons Continental Rises Shaping Continental Shelves

31. Continent Subsurface rock Continental rock Wave-cut terrace Sediment from beach erosion RiverRiver sediment Sediments Water-deposited sediment Coral reef, volcano, or island Stepped Art Fig. 3-12, p. 56

32. Ocean Bottom Ocean basin –abyssal plains and hills –seamounts –ridges and rises –trenches and island arcs Life on the ocean floor –continental shelves are highly productive –life on the abyssal plains is not abundant, no sunlight, no photosynthesis

36. Composition of the Seafloor Sediment—loose particles of inorganic and organic material

37. Composition of the Seafloor Hydrogenous sediments –formed from seawater through a variety of chemical processes –e.g. carbonates, phosphorites, manganese nodules Biogenous sediments –formed from remains of living organisms –mostly particles of corals, mollusk shells, shells of calcium carbonate or silicious planktonic organisms

39. Composition of the Seafloor Terrigenous sediments –produced from continental rocks by the actions of wind, water, freezing, thawing –e.g. mud (clay + silt) Cosmogenous sediments –iron-rich particles from outer space, land in the ocean and sink to the bottom

41. Finding Your Way around the Sea Maps and charts –Mercator projections –bathymetric charts –physiographic charts

45. Finding Your Way around the Sea Reference lines –latitude –longitude –divisions of latitude and longitude

48. Finding Your Way around the Sea Navigating the ocean –principles of navigation a sextant was used to determine latitude based on the angle of the North Star with reference to the horizon longitude determined using chronometer

50. Finding Your Way around the Sea Navigating the ocean –Global Positioning System (GPS) utilizes a system of satellites to determine position GPS measures the time needed to receive a signal from at least 3 satellites, and calculates position