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  • 1. Depositional Shorelines A bay barrier, or bay mouth bar, seals off a lagoon from the ocean. A Tombolo is an sand bar that connects an island to the mainland. Barrier islands are long offshore sand deposits that parallel the coast. A spit connects at one end to the mainland and hooks into a bay at the other. © 2011 Pearson Education, Inc.
  • 2. Depositional Shorelines © 2011 Pearson Education, Inc.
  • 3. Depositional Shorelines Tombolo Barrier island © 2011 Pearson Education, Inc.
  • 4. Barrier Islands Common along East and Gulf coasts of the United States Do not exist along erosional shorelines Protect mainland from high wave activity Can migrate landward over time © 2011 Pearson Education, Inc.
  • 5.  Ocean beachBarrier Island  DunesAnatomy  Barrier flat  High salt marsh  Low salt marsh  Lagoon © 2011 Pearson Education, Inc.
  • 6. Barrier Island Ocean Beach – closest part of the island to the ocean Dune – stabilized by grasses; protect lagoon from strong storms Barrier flat – grassy area that forms behind dunes © 2011 Pearson Education, Inc.
  • 7. Barrier Island High and low salt marshes – biologically productive wetlands  Generate peat deposits of decaying organic matter Lagoon – water between barrier island and mainland © 2011 Pearson Education, Inc.
  • 8. Barrier Islands Migrate landward over time due to rising sea levels Older peat deposits found on ocean beach © 2011 Pearson Education, Inc.
  • 9. Deltas Triangular deposits of sediment where rivers empty into oceans or seas  Distributaries carry sediment to ocean © 2011 Pearson Education, Inc.
  • 10. Emerging Shorelines  Shorelines above current sea level  Marine terraces – flat platforms backed by cliffs © 2011 Pearson Education, Inc.
  • 11. Submerging Shorelines  Shoreline below current sea level  Features include  Drowned beaches  Submerged dune topography  Drowned river valleys (estuaries) © 2011 Pearson Education, Inc.
  • 12. Changing Sea Level Two major processes can change sea level:  Local tectonic processes  Global (eustatic) changes in sea level © 2011 Pearson Education, Inc.
  • 13. Changing Sea Level 1. Local tectonic processes  Example: the Pacific coast of the United States is currently being uplifted.  Isostatic adjustments – rebound of Earth’s crust after removal of heavy loads or sinking with application of heavy loads  Ice-loading from glaciers during ice ages © 2011 Pearson Education, Inc.
  • 14. Changing Sea Level 2. Global (eustatic) changes in sea level  Sea level changes worldwide due to Change in… a. amount of available sea water b. in ocean basin capacity © 2011 Pearson Education, Inc.
  • 15. Eustatic Changes in Sea LevelSome Mechanisms Ice ages lock seawater up in ice (glaciation) – sea level goes down Ice melting after an ice age (deglaciation) – sea level rises © 2011 Pearson Education, Inc.
  • 16. © 2011 Pearson Education, Inc.
  • 17. Pleistocene Epoch and Today From about 2 million to 10,000 years ago, a series of four ice ages affected Earth. Sea level was at least 120 meters (400 feet) below today’s sea level. If all remaining ice on Earth melted today, sea level would rise another 70 meters (230 feet). © 2011 Pearson Education, Inc.
  • 18. Global Warming and Changing Sea Level  Globally averaged temperatures – about 0.6 C (1.1 F) warmer over last 130 years  Sea level rose 10-15 cm (4-10 in) over past 100 years  As global warming continues, we will see a higher sea level. © 2011 Pearson Education, Inc.