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Earth and Space Science Ms. Pollock Spring 2008 Slide 2 Oceans of the World All oceans part of continuous body of water Atlantic, Indian, Pacific three major oceans Atlantic: Mediterranean Sea, Black Sea, Arctic Ocean Sea part of an ocean nearly surrounded by land Pacific: largest; area and volume greater than Atlantic and Indian combined; deepest Ocean important to water cycle Slide 3 Slide 4 Properties of Ocean Water Mixture of gases and solids dissolved in pure water Believed to contain all natural elements on Earth Oceanographers scientists who study the ocean About 96% pure water 4% dissolved elements 96.5% oxygen and hydrogen 1.9% chlorine 1.1% sodium 0.5% magnesium, sulfur, calcium, potassium, bromine, carbon, strontium, silicon, fluorine, aluminum, phosphorous, and iodine Slide 5 Slide 6 Salts in Ocean Water Sodium chloride most abundant Salinity amount of dissolved salts in ocean water Salinity lowest at major rivers High salinity at poles and in areas of little rainfall and much evaporation Many sources of salt in ocean water Volcanic activity Erosion of land areas by rivers and glaciers Wave action along shorelines Slide 7 Slide 8 Gases in Ocean Water Most abundant nitrogen, carbon dioxide, oxygen Carbon dioxide and oxygen necessary for ocean life Photosynthesis Cellular respiration Amounts of gases dependent on depth Most at surface Sunlight penetration Amounts of gases also affected by temperature More gases at poles Density higher to sink gases Slide 9 Slide 10 Temperature of Ocean Water Sun major source of heat Water temperature greatest at surface Water mixed by waves and currents to dissipate heat Surface zone where water is mixed by waves and currents Temperature fairly consistent within surface zone Change not result of depth, but of season and location Warm closer to equator Coldest in winter season Slide 11 Slide 12 Temperature of Ocean Water Quick decrease in temperature below surface zone Thermocline zone of rapid temperature change Does not mix easily with warm or cold water Transition zone Deep zone area of very cold water that extends from the thermocline down Three zones not found in polar regions Slide 13 Slide 14 Topography of the Ocean Floor Similar to continental topography Higher mountains, deeper canyons, larger, flatter plains More volcanoes, more frequent earthquakes Rock formation different from continental rocks Thinner crust Slide 15 Slide 16 Edges of the Continents Continental margin area where underwater edge of continent meets ocean floor; more part of land than ocean Shoreline not end of continent Just position of sea level Continent extends into ocean Continental shelf relatively flat part of continental margin covered by shallow ocean water; slopes gently down from shoreline Width varied Best fishing areas Location of many natural resources Slide 17 Slide 18 Edges of the Continents Continental slope boundary between continental crust and oceanic crust; deep plunge 4 to 5 km Submarine canyons deep V-shaped valleys that have been cut in hard rock; can be very deep Cut across continental slope and continental shelf Monterey Submarine Canyon 2000 meters deep (deeper than Grand Canyon) Believed to be formed by turbidity currents (underwater avalanche) Slide 19 Slide 20 Slide 21 Ocean Floor Features Abyssal Plains large flat areas Larger in Atlantic and Pacific due to many rivers Close to shore thick mud, sand, and silt Further out remains of many microscopic organisms Seamounts underwater mountains formed from volcanoes more than 1000 meters above ocean floor Over 1000 located More in Pacific May rise above surface of water to form islands Many flat-topped Slide 22 Slide 23 Ocean Floor Features Guyots flat-topped seamounts Result of wave erosion Trenches long, narrow crevices Up to 11,000 meters deep More in Pacific Midocean ridges underwater mountain ranges Almost continuous belt Molten material from mantle flows to surface, cools and piles up to make new crust. Divided frequently by rift valleys (crevices) Slide 24 Slide 25 Ocean Floor Features Reefs large masses and ridges of limestone rocks Only in tropical waters (warmer than 18 C) Shallow depth (less than 55 m) Three types of coral reefs Fringing touch shoreline of volcanic island; usually less than 30 meters wide Barrier separated from shore by lagoon; wider than fringing reef, further sunken Atoll surrounding island work away and sunk beneath waves; far out into ocean Slide 26 Slide 27 Ocean Life Zones Ocean home to wide variety of plant and animal life Sunlight penetration Temperature Water pressure Plants and animals classified into three major groups by habits and depth of ocean water habitat Plankton Nekton benthos Slide 28 Slide 29 Ocean Life Zones Plankton float at or near surface of ocean Much sunlight Depth of 1 meter to 200 meters Very small (many microscopic) Drift with currents and tides Food for larger organisms, such as whales Nekton forms of ocean life that swim Whales, dolphins, squid, fish Able to search for food and avoid predators Near surface to ocean floor Slide 30 Ocean Life Zones Nekton, contd. Move from one area of ocean to another Remain in favorable environmental conditions Benthos organisms that live on ocean floor Plants in shallow waters Barnacles, oysters, starfish, crabs Sea anemones that attach to ocean floor Shore areas to deepest parts of ocean Slide 31 Intertidal Zone Between low and high-tide lines Most changeable zone of ocean Difficult for living things to exist tides and breaking waves Anemones, crabs, clams, mussels, seaweed Many attached to rocks and sand of shore Some burrow for protection. Slide 32 Slide 33 Neritic Zone Low-tide zone to end of continental shelf Depth up to 200 meters Abundant sunlight Low water pressure Consistent temperature Floor covered with seaweed Many different animals fish, clams, snails, whales, lobsters Source of most seafood Slide 34 Slide 35 Open Ocean Two open-ocean zones: bathyal zone and abyssal zone Bathyal continental slope down 2000 meters No sunlight at bottom Squid, octopus, large whales Few plants Abyssal 2000 meters down Average depth 6000 meters Large, flat plains of ocean No sunlight, high water pressure Little food Slide 36 Slide 37 Mapping the Ocean Floor First expedition in 1872; Challenger 3 year exploration to measure ocean depth with piano wire Collections of animals, plants, and ocean water Many modern instruments involved (Seasat) Only indirect measurement Underwater cameras Corers Diving vehicles Echo sounding, radar, sonar, seismographic surveys Slide 38 Motions of the Ocean Ocean water in constant motion Three basic motions Up and down wave movement Ocean currents Rise and fall of tides Slide 39 Waves Pulses of energy that move through the ocean Set in motion by wind, earthquake, gravitational pull of moon Begin as ripples on surface take appearance of moving water Particles in place as energy passes from one to another Energy moving forward and downward Little wave motion at great depth Height of surface waves dependent on wind speed, time of wind blowing, and distance wind blows Slide 40 Slide 41 Wave Characteristics Highest point crest Lowest point trough Horizontal distance between crests or troughs wavelength Out in ocean, waves same distance apart for thousands of km, so wavelengths constant (swells) Slow down near shore closer and closer together, decrease in height; crash forward and surge onto shore Water flows back to ocean - undertow Slide 42 Tsunamis Largest ocean waves Caused by underwater earthquakes, volcanoes, and landslides Very long wavelengths, very deep Carry huge amount of energy In shallows pile close together and very high Energy concentrated in small area and volume Can reach 35 meters or greater height at shore Slide 43 Slide 44 Currents Streams of motion beneath the surface of the ocean Caused by wind patterns and differences in water density Surface currents caused mainly by wind patterns Depth of several hundred meters Some warm-water and some cold-water currents Temperature dependent on point of origin Some travel long distances, some short. Continuous worldwide pattern of circulation large, almost circular pattern (Coriolis effect) Can carry large amounts of material Slide 45 Slide 46 Currents Deep currents caused mainly by differences in water density deep in ocean Affected by temperature and salinity Cold water more dense than warm water Saltier water more dense than less salty water Most flow in opposite direction of surface currents Densest water on Earth at Antarctic coast Rising of deep cold currents causes upwelling Upwelling raises rich nutrients from the ocean bottom. Slide 47 Slide 48 Tides Regular rise and fall of ocean water caused by gravitational attraction among Earth, moon, and sun Bulge of ocean in two places Side of Earth facing moon and side of Earth facing away from moon High tide created by bulging Low tide between bulges Two highs and two lows every 24 hours Some highs higher than others, some lows lower than others Varies with moon phases Slide 49