Geography and Oceanography - Chapter 5 pot

Creation, Aging and Recycling of the Ocean Floor How is the ocean floor made? Why does the ocean floor get deeper with age? How are volcanic arcs made and why are they so dangerous? Formation of Ocean Lithosphere Formation of Ocean Lithosphere Formation of Ocean Lithosphere Mid-ocean ridges global circuit of plate divergence youngest ocean floor shallowest ocean floor Architecture of oceanic plates seismic profiling ocean drilling fossil slivers of ocean floor Seismic Profiling (sound energy) Ocean Drilling  International program (20 nations; began 1968)  2-month cruises  Deepest hole: 2 km But, new vessel will drill to >6km! Fast vs. Slow Spreading Fast Spreading Ridge (10-20 cm/yr) Slow Spreading Ridge (1-5 cm/yr) Mid-Ocean Ridges Uniform process of mantle melting, lava freezing - magma chambers - effects of spreading rate - segmentation Ocean Crust Layering Superfast Spread Crust Mission to Hole 1256D Superfast Spread Crust Mission to Hole 1256D Superfast Spread Crust Mission to Hole 1256D Superfast Spread Crust Mission to Hole 1256D [...]... Crack sealing and sedimentation Hydrothermal Vent Sites Hydrothermal Vents Video The ocean floor ages and accumulates sediments Plate Aging and Recycling Slab sinking denser than asthenosphere Plate Subduction and Melting Pacific NW Mt St Helens Water, from slab, promotes mantle melting and leads to explosive danger of arc volcanoes Krakatoa (1883) Tambora (18 15) Toba (71,000 B.C.) -3 000 times as... melting and leads to explosive danger of arc volcanoes Krakatoa (1883) Tambora (18 15) Toba (71,000 B.C.) -3 000 times as big as Mt St Helens - Sulfuric acid and dust blocked sunlight, reducing temperatures 5 C for several years - May have reduced human population to . began 1968)  2-month cruises  Deepest hole: 2 km But, new vessel will drill to >6km! Fast vs. Slow Spreading Fast Spreading Ridge (1 0-2 0 cm/yr) Slow Spreading Ridge ( 1 -5 cm/yr) Mid-Ocean Ridges Uniform. lava freezing - magma chambers - effects of spreading rate - segmentation Ocean Crust Layering Superfast Spread Crust Mission to Hole 1 256 D Superfast Spread Crust Mission to Hole 1 256 D Superfast. to Hole 1 256 D Superfast Spread Crust Mission to Hole 1 256 D Superfast Spread Crust Mission to Hole 1 256 D Mineralized Volcanic Breccia (102 7-1 029 mbsf) o o 1 0 c m Sea floor deepens with distance