The Coast

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					The Coast
       Chapter 11 Homework
•   Coast                •   Sea stack
•   Shore                •   Berm
•   Beach                •   Tombolo
•   Moraine              •   Accretion
•   Delta                •   Jetty
•   Alluvial Plain       •   Groin

    Questions pg 307 2,4,7,9,12,14
            Major Zone
• Coastal zone: The area that is changed
  by the processes of the sea from the
  breaker zone to the uplands of the
• Shore: Outer limits of the waves down
  to the area that the waves directly
          Types of Coast
• Primary Coasts
  -Sea level rise
  -River runoff erosion
  -Tectonic plate moving
     Types of Coast Cont.
• Secondary Coast: formed by marine
  -Wave Action
         Barrier Beaches
• Characteristics of Barrier Beaches
    A. Elongated narrow landforms
    B. Composed of sand and other loose
    sediments transported by waves,
    currents, storm surges, and wind.
    C. Dynamic (Eroding or accreting)
    D. Low land masses
     Barrier Beaches Cont.
• Functions of Barrier Beaches
     A. Protect mainland, sounds, salt
     marshes, sand, and mud flats from
     ocean energies (wave attack)
     B. Locations for lighthouses, fishing
     communities, Coast Guard stations
  and ports.
     C. Aesthetic Value
     D. Valuable habitat for mammals,
     waterfowl, fish, and shellfish
  Barrier Beaches Cont.
   E. Development/Tourism Leads
to research to determine their
geologic    and ecologic
characteristics to define
   barrier carrying capacities and
   susceptibility to storm damage
    Barrier Beaches Cont.
• Location of Barriers
    A. Found from the rocky headlands
    of Maine to the salt flats of south
    B. Protect 2700 miles of shoreline
      Barrier Island Types
• Barrier Spit- barrier beaches that are
  attached at one end to a source of
  sediment and extend into open water.
  – Caused by long shore currents moving
    abundant sand and gravel from eroding
  – Types of Spits
    • Simple
    • Double
    • Recurved
    • Complex
Barrier Island Types Cont.
– Location of barrier spit
– Maine
  • New Jersey
  • Massachusetts
  • Virginia
  Barrier Island Types Cont.
• Barrier Island- barrier beaches not
  connected to source of sediment (most
  commonly recognized offshore
• Classified according to
  – Tide- Microtidal- less than 6 feet and
    Mesotidal- 6-12 feet
  – Sand supply- Transgressive- sand
    deficiency and Regressive- accretion-
    multiple dune ridges)
  Barrier Island Types Cont.
• Types of Barrier Islands
  – Microtidal Transgressive- Outer Banks
  – Microtidal Regressive- Bogue and
    Shackleford Banks
  – Mesotidal Transgressive- Morris and
    Caper Islands in SC
  – Mesotidal Regressive- Bulls Island in SC
  – Capes- Barrier islands that project in to
    the sea to form a right-angled shoreline.
    Hatteras, Lookout, Fear
  Barrier Island Types Cont.
• Bay Barriers- barrier beaches that are
  connected at both ends to headlands-
  Northern New England
  – Types of bay barriers
    • Baymouth Barriers- connect head lands
      together- Martha’s Vineyard, Mass. and RI
    • Tombolo- Island attached to headland (glacial
      or volcanic in origin) EX California Coast
  Origin of Barrier Beaches
• Ridge submergence
  – As sea level rose, dune ridges on seaward
    edge of mainland became barrier islands.
  – Lower areas behind these ridges were
    flooded, creating lagoons (sounds).
  – Major means of barrier formation along
    the Southeast Atlantic USA
  Origin of Barrier Beaches
• Submarine bar upbuilding
  – Material from the nearshore bottom is
    transported landward by waves to form an
    offshore bar
  – Eventually builds above sea level as
    barrier beach
  – Some small Gulf Coast barrier islands
    have originated this way.
  Origin of Barrier Beaches
• Spit Accretion
  – Sand is transported by littoral drift
    (longshore currents) and builds up to
    form a spit
  – If inlets form the spit may become an
  – Example- Barrier island system of Cape
    Cod and south shore of Long Island
  Origin of Barrier Beaches
• Delta sediment changes
  – Small barriers form on deltas through
    wave action and reworking of river
  – Example- Mississippi Delta and along the
    coast of Maine
  Barrier Evolution- “The Sand
     Sharing System" Cont.
• Causes of evolution of barriers
  – Rate of sea level rise- If sea level rises 1 ft,
    the barrier must move 100-1,000 ft or it
    will drown
  – Sand supply- from offshore and from other
  – Sea Energy-storms
  – Littoral drift- average 500,000 cubic yards
    per year. 1,000,000 cubic yards at Cape
Barrier Evolution- “The Sand
   Sharing System" Cont.
–   Inlet Dynamics
–   Overwash
–   Dune migration
–   Human Intervention
  Barrier Evolution- “The Sand
     Sharing System" Cont.
• Examples of barrier evolution
  – Storm erosion and natural beach repair
    • During storms sand is carried offshore to
      submerged ridges (storm bars)
    • Gentle waves cause these bars and runnels
      (troughs) to migrate landward and rejoin
    • A change in any factor may result in a
      changed beach
 Barrier Evolution- “The Sand
    Sharing System" Cont.
• Landward migration
  – This is often called erosion, but the term
    retreat is more accurate.
  – Barriers have been migrating landward
    since their creation. Have moved 20-70
    miles landward
  – Transported sand buries backbarrier
    environments. New marshes develop
    farther landward on leading edge of new
Barrier Evolution- “The Sand
   Sharing System" Cont.
– Evidence 1) Core samples of beaches
  show marsh peat under dunes. 2) Salt
  marsh peat, oyster and tree stumps
  exposed on beach after storm
– Migration speed varies 1) Nauset Island,
  Mass. Has rapid migration. 2) Hatteras Is.
  Has remained static and is eroding on
  ocean and sound side
  Barrier Evolution- “The Sand
     Sharing System" Cont.
• Causes of sand transportation to back
  barrier environments
  – Storms- Major amount of sand transport
    occurs during 1) Northeasters
                   2) Hurricanes
  – Inlet dynamics
    • During a storm, waves wash over at low places
      in dune
    • High water blown by winds create inlet
    • Creation of flood tidal delta in bay
Barrier Evolution- “The Sand
   Sharing System" Cont.
 • Delta grows
 • Longshore currents cause inlets to migrate
   southward- delta grows more
 • Water path becomes long and tortuous
 • Inlet closes and marsh grows on old flood
   tidal delta
 • Barrier beach is widened
Barrier Evolution- “The Sand
   Sharing System" Cont.
– Overwash Processes
  • Storm surges allow waves to wash over beach
    and push sand from beach and dune zone.
  • Often viewed as a disaster, however it is a
    continuous process. It enables barrier island
    to migrate landward (roll over
  • Overwash fans eventually bury marsh, new
    marsh develops
  • Barrier beach is displaced land ward, but
    ecological units retained.
  • Overwash process depends on barrier
    exposure, orientation, storm frequency, tidal
    range, and vegetation species.
Barrier Evolution- “The Sand
   Sharing System" Cont.
– Dune migration
  • Principle means of landward migration along
    some barriers (Mass.) can be accelerated by
    human intervention.
  • Aeolian transport (wind) results in dune
    formation using sand from beach or overwash
    fan into areas with fences or vegetation to
    anchor sand.
  • Dunes can migrate and bury salt marshes and
    maritime forests. (Jockey’s Ridge)

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