Sea Floor Tectonics Earth Science Chapter 13, p. 164-174 Scotts Mills 2006 April 26, 7:24 AM • Magnitude 3.0 • Depth 19 km http://pasadena.wr.usgs.gov/shake/pnw/STORE/X4261424_06/ciim_display.html Atlantic oceanic ridge Passive Continental Margin • Continental shelf • Continental slope • Continental rise Passive continental Margin— location Passive continental Margin—cross section Deep sea sediment fans Turbidity current Discovery of Turbidity Currents Sea-floor landforms—California Active Continental Margins • Narrow continental shelf • Deep sea trench catches terrigenous sediment • ‘Accretionary Wedge’ Active continental Margin—location Active continental Margin—cross section Deep-Ocean Trenches • Active continental margins • Other convergent plate locations • Most are in the Pacific Ocean Atlantic Ocean Floor Pacific and Indian Ocean Floor Kaiko •ROV • 10,990 m • 1995 Challenger Deep shrimp http://www.mext.go.jp/english/news/1998/07/980705.htm Convergent Lithospheric Plates • Oceanic plate is subducted • Deep-ocean trench is formed • Volcanism above subducted plate Atoll formation Atoll Oceanic Plateaus • Figure 10-19—Oceanic Plateaus Alvin • Manned • 4000 m maximum depth Oceanic Ridge--Atlantic Oceanic Ridge—Indian Oceanic Ridge—Pacific Oceanic plate divergence http://www.soc.soton.ac.uk/CHD/classroom@sea/carlsberg/science/constructive_margins.html Rift valleys on oceanic ridges Formation of Black Smoker http://www.paedquest.de/Riff_Tiefsee_Mangroven_neu/tiefsee/content/geobsm01.html Black Smoker with tube worms http://www.pbs.org/wgbh/nova/abyss/life/extremes2.html Pacific Lithosphere Action http://www.soc.soton.ac.uk/CHD/classroom@sea/carlsberg/science/oceanic_constr.html Offshore oil platform Methane Hydrate sample Methane Hydrate burning Salt production Manganese Nodules.