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Measuring bathymetry Ocean depths and topography of ocean floor Bathymetric techniques Echo sounding/Sonar Reflection of sound signals Side-scan sonar Towed behind research vessel (ship) Ex. GLORIA Bathymetric techniques Fig. 4.4 - Seismic Profiling Bathymetric techniques, cont… Fig. 3.2 Bathymetric techniques, cont… Satellite Measurements Ocean floor features cause sea surface to rise Marine provinces 3 major provinces Continental margins Deep-ocean basins Shallow-water areas close to shore Deep-water areas farther from land Mid-ocean ridge Submarine mountain range Continental margins Passive or active Passive (Atlantic-type) Not close to any plate boundary No major tectonic activity east Ex: coast of United States Continental margins, cont… Active (Pacific-type) Associated with convergent or transform plate boundaries Much tectonic activity Convergent active margin Oceanic-continental convergence western South America Ex: Continental margins, cont… Transform active margin Associated with transform plate boundaries Ex: Coastal California along the San Andreas fault Continental margins Fig. 3.6 Continental shelf Extends from shoreline to shelf break Shallow, gently sloping Continental slope Submarine canyons cut into slope by turbidity currents Mixture of seawater and sediments Move under influence of gravity Continental rise Transition between continental crust and oceanic crust Deep ocean basin features Depths greater than 4000 m Abyssal plains Volcanic peaks Ocean trenches Oceanic ridges and rises Abyssal plains Very flat depositional surfaces from base of continental rise Volcanic peaks Poke through sediment cover Below sea level: Seamounts Ocean trenches Associated with subduction zones Deepest parts of ocean Ex. Mariana Trench Mid-ocean ridge and rises Longest mountain chains Basaltic lava Divergent plate boundary Volcanic features of mid-ocean ridge Hydrothermal vents Heated subsurface seawater migrates through cracks in ocean crust