chapter 18 oceanography
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Chapter 18 Oceanography

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Chapter 18 Oceanography. 18.1 The Seafloor. Ocean Basin Features The continental shelf is a gradually sloping end of a continent that extends out under the ocean Along some coasts it can extend long distances Atlantic and gulf coasts – 100 to 350 km Pacific Coast – 10 to 30 km.

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18 1 the seafloor
18.1 The Seafloor
  • Ocean Basin Features
    • The continental shelf is a gradually sloping end of a continent that extends out under the ocean
      • Along some coasts it can extend long distances
      • Atlantic and gulf coasts – 100 to 350 km
      • Pacific Coast – 10 to 30 km
The continental slope is the end of the continent extending form the outer edge of the shelf down to the ocean floor
    • The slope is steeper than the shelf
    • Beyond the slopes lie the trenches, valleys, plains and ridges
  • Abyssal plains are the flat seafloors in the deep ocean, formed by deposition of sediment by ocean currents
    • 4000 to 6000 km deep in the ocean
Plate Boundary Structures
    • The place where new ocean floor forms is called the mid-ocean ridge
      • Resembles a chain of mountains
      • Magma from the Earth’s interior oozes from these cracks
    • Seamounts are inactive volcanic cones found on the ocean floor
    • Seamounts that extend up out of the ocean are volcanic islands.
On the ocean floor crustal plates converge at trenches
  • A trench is a long, narrow steep-sided depression in the ocean floor where one crustal plate is forced beneath another
    • Most trenches are found in the Pacific Basin
    • Often longer and deeper than any valley on any continent
    • Not only are they deepest places on Earth, they are also the most geologically active
    • Seaquakes and chains of volcanoes often occur along trenches
Mining the seafloor
    • There are many petroleum and natural gas deposits in continental shelf sediments
      • About 20% of the world’s oil comes from under the seabed
    • Other deposits on the continental shelf are also mined
      • Placer deposits form where rivers meet oceans and can no longer carry their sediments
      • Sand, metals, and even diamonds are mined from placer deposits in some regions
Valuable minerals are also found in deep water
    • Minerals can form where molten substances and hot water are forced into cool ocean water
    • Other minerals precipitate out and form solids on the ocean floor
18 2 life in the ocean
18.2 Life in the Ocean
  • Life Processes in the Ocean
    • All life is water based
      • Life began in the oceans
      • Water is used for all the basic processes of living things
    • Nearly all the energy used by organisms ultimately comes from the sun
    • Chlorophyll-containing organisms use the sun’s energy to make food
Another type of food web in the ocean does not depend on sunlight
    • In areas along the mid-ocean ridges, bacteria produce food and oxygen by using dissolved sulfur compounds that escape from magma (chemosynthesis)
  • Ocean water also provides an easy way for organisms to reproduce
  • Seawater also provides a thermally stable environment for organisms
Ocean Life
    • Plankton are tiny marine algae and animals that drift with currents
    • Nekton are animals that actively swim, rather than drift with the currents
      • Nekton include all swimming forms of fish and other animals
      • Some deep dwelling organisms have special light-generating organs for attracting live food
    • Benthos are bottom dwellers
      • plants, algae, and animals that live on the seafloor
      • Some are attached, others burrow
Corals are organisms that live attached to the seafloor
    • Obtain food by stinging their prey
    • A reef is a rigid, wave-resistant structure built from skeletal materials and calcium carbonate
18 3 pollution and marine life
18.3 Pollution and Marine Life
  • Ocean Pollution
    • Pollution is the introduction by humans of harmful waste products, chemicals, and substances into an environment
    • A pollutant is a substance that causes damage to an organism by interfering with biochemical processes
    • Most ocean pollution is concentrated along the coasts
Industrial waste sometimes gets into seawater
  • Solids such as plastic bags can entangle animals
  • Pesticides used in farming and on lawns run off and reach the ocean
  • Crop fertilizers and sewage can reach the oceans and cause rapid growth of some algae
  • Oil from oil spills and wastewater can pollute the ocean
  • Soil and silt can also accumulate in coastal areas due to erosion upstream