Ocean Topography

Mapping the Ocean Floor Bathymetry measurement of ocean depths Charting topography of ocean floor Mapping via Sonar – sound navigation ranging Satellites – using microwaves Submersibles

Ocean Regions Continental Margins Ocean basin floor Mid ocean Ridge

Continental Margin Zone of transition between continent & ocean basin floor Undisturbed sediment covers continental margin

Continental Margin Atlantic – Pacific Thick layers undisturbed sediment Little volcanic or earthquake activity Pacific Narrow continental margin Volcanic & earthquake activity

Continental Margin Continental shelf Continental slope Continental rise

Continental Shelf Gently sloping submerged surface extending from shoreline Associated with coastal plain Part of continent located under water Undersea during interglacial periods Mineral deposits Large reservoirs of oil & natural gas Huge sand & gravel deposits Can be shallow or deep

Continental Slope Steep gradient leading to deep-ocean floor Seaward edge of continental shelf Submarine canyon Seaward extension of a valley that was cut on the continental shelf Occurred during time sea level was lower Canyon carved into outer continental shelf, slope, and rise Due to turbidity currents Turbidity currents – downslope of sediment laden water water created when sand and mud on the continental shelf and slope are dislodged and thrown into suspension

Continental Rise Gentle slope Generally smooth surface Built up by shedding of sediments from the continental block From base of continental slope to abyssal plain

Ocean Basin Floor Ocean basin floor Deep ocean trenches Area of the deep-ocean; between continental margin and oceanic ridge Deep ocean trenches Sites of plate convergence One moving plate descends beneath another Plunges back into mantle Long, narrow creases Most at margins of Pacific Challenger Deep- 11,022 meters deep

Ocean Basin Floor Abyssal plain Deep, flat or very gently sloping areas Between foot of continental rise & mid oceanic ridge Thick accumulation of fine sediment Found in all oceans Atlantic most extensive due to few trenches

Ocean Basin Floor Abyssal hills Hills along the ocean floor 100 to 2000 meters high, several km across

Ocean Basin Floor Seamount Volcanic peak rises from deep-ocean floor Up to 1000 meters above deep-ocean floor Steeped sided, cone shaped Found floors of all oceans, greatest number in the Pacific. e.g. Hawaiin-Emporer Seamont Chain; From the Hawaiin Islands to Aleutian trench

Ocean Basin Floor Guyot Table mount Flat top seamount Formed by erosion of seamount via waves, winds, atmospheric processes

Mid Ocean Ridge Found near center of ocean basins Interconnected system of underwater mountains Developed on newly formed crust (sea floor spreading) Winds through all major oceans 70,000 km long 1000 to 4000 km wide Broken into segments, offset by transform faults Oceanic spreading center

Mid Ocean Ridge Rift zone Found in highest part mid ocean ridge Narrow trench (rift valley)

Mid Ocean Ridge Hyperthermal vents Form along mid ocean ridge Mineral rich water heated by hot newly formed oceanic crust Escapes through cracks in new crust to surrounding cold water