CH 14.1 The Ocean Floor Oceanography – the study… 71 % of earth covered by oceans Southern Hemisphere is 81 % water Northern Hemisphere is 61 % water 4 major ocean basins Pacific – largest and deepest Atlantic – narrow Indian Arctic

Mapping the Ocean Floor The topography of the ocean floor is as diverse as that of continents Bathymetry – measurement of ocean depths HMS Challenger – 1872 - 1876 SONAR – Sound Navigation and Ranging Satellites – Surface height from oc floor Submersibles – manned and remote

14.2 Ocean Floor Features 3 major regions 1. Continental margins 2. Ocean basin floor 3. Mid-ocean ridges

1 - Continental Margins Passive margins – wide shelves, no trench, sediment accumulation Active margins – narrow shelf, trenches, volcanoes and EQs Continental shelf – relatively flat extension of continent underwater Continental slope – sloped surface beyond the shelf break (submarine canyons) Continental rise – base of cont slope (turbidity currents)

2 - Ocean Basin Floor Between cont margin & mid-ocean ridge Covers 30% of earth Deep ocean trenches (subduction) Mariana Trench Abyssal plains - Deep and flat Seamounts - Underwater volcanoes Guyots - Flat topped underwater volcanoes

3 - Mid-ocean Ridges Underwater mountain ranges Long and wide Rift zone Transform faults Seafloor spreading Hydrothermal vents

14.3 Seafloor Sediments Can be classified according to their origin 3 categories Terrigenous – originates on land Biogenous – biological in origin Calcareous ooze Silicous ooze Hydrogenous – originates from ocean water Manganese nodules

Seafloor Resources Oil and natural gas Gas hydrates Sand and gravel Manganese nodules Evaporative salts