Oceanography Chp 8

• Shore


  Where ocean meets land
• Coast


  Larger zone affected by the processes occurring at the boundary
• Coast


  • Location varies
  • Shape influenced by uplift and subsidence, erosion, redistribution and deposition

  
• Causes of changes in sea level


  • Global glaciations
  • High rates of seafloor spreading
  • Temperature increase may increase volume
  • Tectonic motions and isostatic adjustments
  • Wind and current, seiches, storm surges, El Nino and La Nina

  
• Erosional coastal processes and landforms

  • Found commonly on active margins
  • Types: sea cliffs, sea caves, sea arches, sea stacks, wave cut terraces

  
• Erosion rates depend on hardness of rock, strength of wave action, local range of tides, biological activity, and currents
• Depositional coastal processes and landforms

  • Common on passive margins
  • Types: Atlantic coastal plains, barrier spit, bay barriers, tidal flats, salt marshes, inland lagoon, tombolo, beaches

  
• Relationship between particle size and beach slope


  Depends on wave energy, particle shape, porosity of the packed sediments

  
• Longshore drift


  1. Wave driven movement of sand along the exposed beach

  2. Current and driven movement of sand in the surf zone just offshore
• Longshore current and beach drift

  Parallel current generated in surf zone transports sediment along shore as longshore drift
• Maintaining beaches


  • Jetties
  • Groins
  • Breakwaters
  • Beach nourishment
• Introducing a breakwater


  Reduces longshore drift
• Coastal cells are defined by headlands and other barriers that interrupt the longshore transport of sediment
• Bay mouth bars form at the entrance to bays and estuaries
• Barrier islands form parallel to the coast, separated from the mainland by a lagoon or marsh
• Deltas do not form at the mouth of every river, they need a broad continental shelf for sediments to deposit on, and tidal range is usually low with mild waves and currents
• River dominated deltas


  • Form in protected seas, dominated by strong flow of freshwater and continental sediments, terminate in set of distributaries
• Tidal deltas


  • Freshwater discharge overpowered by tidal currents, currents mold sediments into long islands parallel to river flow and perpendicular to the trend of the coast
• Wave dominated deltas


  • Smaller than tide or river dominated deltas, smooth shoreline punctuated by beaches and sand dunes, has one main exit channel
• Coral reefs and mangroves are important coastal ecosystems
• Estuaries


  Body of water partially surrounded by land where fresh water from river mixes with ocean water
• Types of estuaries


  • Drowned river mouth
  • Fjords
  • Bar-built
  • Tectonic
• Characteristics of estuaries


  • Circulation patterns determined by shape of estuary, volume of river flow at head, and range of tides at mouth
• Estuaries support a lot of living organisms, have nutrients, sunlight and protection from wave shock, and serve as nurseries for marine animals
• Estuaries are valuable for commercial development