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