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Chapter 12 – THE OCEANS

Chapter 12 – THE OCEANS. The Oceans. Ocean basins No geologic record of time before water Origin of water on Earth is debated 1 st proposal = water originated inside Earth 2 nd proposal = water arrived from outer space via meteorite impacts. Ocean basins Earth has 4 huge water basins

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Chapter 12 – THE OCEANS

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  1. Chapter 12 – THE OCEANS

  2. The Oceans Ocean basins No geologic record of time before water Origin of water on Earth is debated 1st proposal = water originated inside Earth 2nd proposal = water arrived from outer space via meteorite impacts

  3. Ocean basins Earth has 4 huge water basins Pacific Ocean Atlantic Ocean Indian Ocean Southern Ocean *Arctic Ocean Cover 71% of Earth’s surface The Oceans

  4. Composition of seawater Salinity Measure of salt content of solution Seawater salinity ranges 3.3 - 3.7% Elements in seawater come from: Chemical weathering of rock Volcanic eruptions & black smokers Evaporation of surface water (increases salinity) Freezing of seawater (increases salinity) The Oceans

  5. Layers in the ocean 3 major layers in oceans in which density differs: Surface layer ( 2%; warmest) Thermocline (18%; just above freezing point) Deep Zone (80%; temperature low & constant) The Oceans

  6. Ocean currents Surface currents Christopher Columbus The Oceans

  7. Ocean currents Deep currents: “Great Ocean Conveyor Belt” (thermohalinecirculation) North Atlantic Deep Water Antarctic Bottom Water Gulf Stream The Oceans

  8. How oceans regulate climate Oceans moderate coastal climates Continental interiors = more extreme Conveyor belt re-distributes heat from tropics to poles Elimination of conveyer belt (e.g., Gulf Stream) could cause ice age The Oceans

  9. Where the Ocean Meets Land Changes in sea level Global volume change Barely noticeable in human lifetime Account for great change in position of shore line over geologic time Global warming = sea level rise Current global warming = 2.4 mm/year rise Global cooling = sea level drop

  10. Changes in sea level Tides Regular daily cycle of rise & fall of sea level resulting from gravitational action of Moon, Sun, & Earth Where the Ocean Meets Land

  11. Changes in sea level Tides Run-up height Tidal range Spring tide Neap tide Tidal bore Where the Ocean Meets Land

  12. Changes in sea level (continued) Waves Ocean waves receive energy from wind Surf “Broken”, turbulent water found between line of breakers &shore Rip currents Wave refraction Where Ocean Meets Land

  13. Changes in sea level continued Erosion & transport of sediment by waves Longshore current Current in surf zone; flows parallel to coast Beach drift Particles driven up/down beach slope by wave action Where Ocean Meets Land

  14. 3 kinds of shorelines & coastal landforms Rocky coasts Wave-cut cliff Coastal cliff cut by wave action at base of rocky coast Wave-cut bench Marine terrace Where the Ocean Meets Land

  15. 3 kinds of shorelines & coastal landforms Beach Wave washed sediment along coast Where the Ocean Meets Land

  16. Kinds of shorelines & coastal landforms Barrier Island Long, narrow, sandy island offshore & parallel to low land coast Spit Lagoon Where Ocean Meets Land

  17. Kinds of shorelines & coastal landforms Tombolo Bay barrier Estuary Where Ocean Meets Land Estuary

  18. Kinds of shorelines & coastal landforms Reefs Hard structure on shallow ocean floor, built by coral Polyps- tiny coral animals that deposit calcium carbonate Fringing reef Barrier reef Atoll Highly productive ecosystems Where Ocean Meets Land

  19. Active continental margin Located near plate boundaries Narrow continental shelf & coastal plain I.e. Pacific coast Passive continental margin Not located near plate boundaries Wider continental shelf & coastal plain I.e. Gulf coast; Atlantic coast Coastal Processes & Problems Lab

  20. Waves Crest Trough Wave height (crest – trough) Wavelength (crest to crest) Wave period (time it takes 2 crests to pass fixed point) Factors that affect waves Wind speed Wind duration Fetch Coastal Processes & Problems Lab

  21. Coastal erosion & deposition Headlands = erosion (energy concentrated) Bays = deposition (energy dispersed) Wetland erosion Wetlands = barriers for storm surge & large waves Mississippi River delta wetlands being eroded due to human actions River modifications Coastal Processes & Problems Lab

  22. Human modification of coastlines Groins Jetties Breakwaters Seawalls Problems Coastal Processes & Problems Lab

  23. Hurricane ingredients Atmospheric disturbance Warm ocean water Light upper atmospheric winds Hurricane damage Storm surge High winds Rainfall & flooding Tornadoes Coastal Processes & Problems Lab

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