1. Chapter 3 Geology of the Ocean

2. Oceans cover more than 80% of the southern hemisphere but only 61% of the northern hemisphere

3. 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

4. Figure 3-3 THE WORLD OCEAN.

5. 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

6. Figure 3-4 (upper) COMPOSITION OF THE EARTH.

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

8. Figure 3-5 THE SUPERCONTINENT PANGEA.

9. 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

10. Figure 3-6 FORMATION OF OCEANIC CRUST AND MOUNTAINS.

11. Figure 3-7 SEAFLOOR SPREADING AND CONTINENTAL DRIFT.

12. 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

13. Figure 3-8 (upper) EARTHQUAKE ZONES AND TECTONIC PLATES.

14. Figure 3-A MAGNETOMETER DATA.

15. Continental Drift Theory of plate tectonics
lithosphere is viewed as a series of rigid plates separated by earthquake belts
divergent plate boundaries: located at mid-ocean 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

16. 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

17. Ocean Bottom Ocean basin Life on the ocean floor
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

18. Figure 3-13 LANDSCAPE OF THE OCEAN FLOOR.

19. 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

20. Figure 3-15 BIOGENOUS SEDIMENTS.

21. 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

22. Figure 3-B AN AMPELISCID AMPHIPOD.

23. 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

24. Figure 3-19 A SEXTANT.

25. 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

26. Figure 3-20 THE EARTH’S TIME ZONES.