The Ocean Basins How Deep is the Ocean? 1 2 Three Major Oceans Three Major Oceans Pacific Atlantic the shallowest ocean (3.3km average depth) Indian second shallowest ocean (3.8km average depth) Pacific Atlantic Indian 3 Pacific the deepest ocean (3.9km average depth) 4 Four Major Ocean Basins Pacific the single largest geographic feature on the planet. Can hold all of the continents and still have space left over. Atlantic half the size of the Pacific with almost parallel continental margins Indian largely a Southern Hemisphere water body Arctic 7% the size of the Pacific 5 What is a SEA? Small area of the ocean that is partially surrounded by land 6 1
Mediterranean Sea Caribbean Sea South China Sea Bering Sea Gulf of Mexico Seas Hudson Bay Japan Sea North Sea Red Sea Baltic Sea East China Sea 7 8 Exploring our Oceans Oceanography is the study of the physical characteristics, chemical composition and life forms of the ocean. What are Submersibles? Underwater research vessels The Alvin The Jason 9 10 Bathymetric Techniques -SONAR Important to help map ocean floor Sound Navigation and Ranging How SONAR works receiver Differences in the time it takes for the sound waves to leave the boat and then return tell scientists how deep the ocean bottom is. ocean surface transmitter 11 ocean floor 12 2
Scientist use explosions to make low frequency sounds. The waves reflected off the sea floor create a profile which provides details about the rock structure beneath the sediments that blanket the seafloor. 13 14 Continental margin: portion of ocean made up of continental crust Continental shelf: flat part of continental margin covered by shallow ocean water Formed by changes in sea level Avg depth = 60 m 15 continental slope: boundary between continental crust and oceanic 16 continental rise: wedge of sediments that separates slope from ocean floor abyssal plain: large flat area on the ocean floor. Appearance due to accumulation of sediments which have buried the rugged ocean floor. seamount: underwater volcanic mountain (1000m) guyot: a flat-topped submerged seamount 17 18 3
trench: deep narrow valleys along the edges of ocean floor Marianas Trench in Pacific ocean is 36,000 ft deep (6mi) deepest point Submarine canyon deep, steep-sided valleys cut into the continental slope by erosion from turbidity currents. Santa Monica Canyon and the Redondo Canyon are examples of submarine canyons 19 mid-ocean ridge: mountain range on ocean floor rift valley: deep crevice in between mountain ranges 20 Continental Margins Passive Continental Margin include the continental shelf, the continental slope, and the continental rise Found along most of the Atlantic Ocean Not associated with plate boundaries Very little volcanism and few earthquakes 21 Active Continental Margin Active Continental Margin the continental slope descends abruptly into a deep ocean trench located between the continent and ocean basin. The continental shelf is very narrow, if it even exists. Occur where oceanic lithosphere is being subducted beneath the leading edge of a continent producing a relatively narrow margin consisting of highly deformed sediments. Located primarily around the Pacific Ocean 22 Active Continental Margin The landward wall of the trench and the continental slope are the same feature. coral reef: limestone structures containing shells of animals that surround volcanic islands 23 24 4
3 Types of Coral Reefs Most reef scientists generally recognize three basic types of coral reefs: (1) Atoll - a roughly circular (annular) oceanic reef system surrounding a central lagoon 3 Types of Coral Reefs (2) Fringing Reef - a reef system that grows fairly close to (or directly from) the shore, with an entirely shallow lagoon or none at all 25 26 3 Types of Coral Reefs (3) Barrier Reef - a reef system that parallel the shore and is separated from it by a wide lagoon that contains at least some deep portions Resources from the Seafloor Energy Resources: Oil and Natural Gas come from the ancient remains of microscopic organisms buried within marine sediments before they could decompose. Gas Hydrates occur beneath permafrost areas under land and under the ocean floor at depths below 525 m. 27 28 Other Resources Sand and gravel includes rock fragments that are washed out to sea and shells of marine organisms Mined by offshore barges using suction dredges Materials of high economic value are associated with offshore sand and gravel deposits: Gem quality diamonds Tin Platinum & Gold Titanium 29 Evaporative Salts Salt deposits, particularly halite are harvested from the ocean. 30% of the world s salt is produced by evaporating seawater. Manganese Nodules Manganese Nodules contain significant concentrations of manganese, iron and smaller concentrations of copper, nickel, and cobalt. 30 5
31 Closure We now know that the ocean floor has mountains, trenches, volcanoes, etc. Explain how people use to think the ocean floor looked and what technology has told us differently. 32 6