Download Chapter 3 - Perry Local Schools

Chapter 3
Geology of the Ocean
Karleskint
Turner
Small
• Oceans cover more than 80% of the
southern hemisphere but only 61% of the
northern hemisphere
Karleskint
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World Ocean
• The ocean today
– 4 major ocean basins:
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Pacific
Atlantic
Indian
Arctic
– Pacific Ocean - largest
– Arctic Ocean - smallest
– Seas - smaller than ocean, essentially
landlocked
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
Continental Drift
• Moving continents
– Continents fit together like pieces of jigsaw
puzzle
– One supercontinent - Pangaea
– Laurasia and Gondwanaland
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
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
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
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
– 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
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
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
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
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