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Chapter 3 Marine Provinces Essentials of Oceanography 7th Edition Bathymetry Bathymetry is the measurement of ocean depths and the charting of the shape or topography of the ocean floor The ocean floor is a highly varied terrain that contains many interesting features Early methods of determining ocean depths involved using a long weighted line (called a sounding line) Bathymetric techniques Echosounders send sound through water to determine water depth and sea floor features Figure 3-1 Bathymetric techniques Side-scan sonar uses a “fish” towed behind a ship to give a more detailed picture of the sea floor Figure 3-2 Bathymetric techniques Low frequency sound is used to determine structure beneath the sea floor Figure 3-3 Bathymetric techniques Satellites measure sea surface elevation, which mimics sea floor bathymetry Figure 3D The hypsographic curve The hypsographic curve shows the relationship between the height of the land and the depth of the oceans Figure 3-4 Major regions of the North Atlantic Ocean floor Continental margin Ocean basin floor Mid-ocean ridge Figure 3-5 Passive versus active continental margins Passive margin No plate boundary Shelf Slope Rise Figure 3-6 Passive versus active continental margins Active margin Plate boundary Convergent Shelf Slope (steep) Trench Transform Continental borderland Figure 3-6 Submarine canyons and deepsea fans Turbidity currents carve submarine canyons into the slope and shelf Debris from turbidity currents creates graded bedding deposits and deepsea fans Figure 3-8a Diver in the La Jolla Submarine Canyon Figure 3-8b Abyssal plains Deep flat areas formed by suspension settling Volcanic peaks poke through the sediment Abyssal hills (seaknolls) Seamounts Tablemounts (guyots) Figure 3-9 Ocean trenches Deepest parts of the ocean Formed by plate convergence Most trenches are in the Pacific Ocean Associated with volcanic arcs Island arc Continental arc Figure 3-10 The mid-ocean ridge Circles the globe like the seam of a baseball Mostly traverses the middle of ocean basins A topographically high mountain range Entirely volcanic in origin Associated with plate divergence In the Pacific Ocean, called the East Pacific Rise In the Atlantic Ocean, called the Mid-Atlantic Ridge Internet flybys of portions of the mid-ocean ridge The Mid-Atlantic Ridge Traverses the center of the Atlantic Ocean Contains a central downdropped rift valley Comes above sea level in Iceland Figure 3-12 Features of the mid-ocean ridge Rift valleys Form when plates split apart Downdropped areas associated with faults and earthquakes Figure 3-13 Features of the mid-ocean ridge Pillow lava Forms when hot lava comes into contact with cold seawater and quickly cools Basalt composition Figure 3-14 Features of the mid-ocean ridge Hydrothermal vents Form when seawater is heated by magma Black smokers emit hot water through chimneys Associated with metal sulfide deposits and unusual lifeforms Figure 3-15 Transform faults and fracture zones Transform Faults Occur between segments of the mid-ocean ridge Transform plate boundaries Movement in opposite directions Figure 3-16 Transform faults and fracture zones Fracture Zones Occur beyond segments of the mid-ocean ridge Not plate boundaries Movement in the same direction Figure 3-16 End of Chapter 3 Essentials of Oceanography 7th Edition