Chapter 3 Geology of the Ocean

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

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

Figure 3-3 THE WORLD OCEAN.

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

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

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

Figure 3-5 THE SUPERCONTINENT PANGEA.

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

Figure 3-6 FORMATION OF OCEANIC CRUST AND MOUNTAINS.

Figure 3-7 SEAFLOOR SPREADING AND CONTINENTAL DRIFT.

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

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

Figure 3-A MAGNETOMETER DATA.

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

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

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

Figure 3-13 LANDSCAPE OF THE OCEAN FLOOR.

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

Figure 3-15 BIOGENOUS SEDIMENTS.

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

Figure 3-B AN AMPELISCID AMPHIPOD.

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

Figure 3-19 A SEXTANT.

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

Figure 3-20 THE EARTH’S TIME ZONES.