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.
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2. Depositional Shorelines
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4. Depositional Shorelines
Tombolo Barrier
island
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5. 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
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6.  Ocean beach
Barrier Island  Dunes
Anatomy  Barrier flat
 High salt marsh
 Low salt marsh
 Lagoon
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7. 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
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8. Barrier Island
 High and low salt marshes – biologically
productive wetlands
 Generate peat deposits of decaying organic matter
 Lagoon – water between barrier island and
mainland
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9. Barrier Islands
 Migrate landward
over time due to
rising sea levels
 Older peat deposits
found on ocean
beach
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10. Deltas
 Triangular deposits of
sediment where rivers
empty into oceans or
seas
 Distributaries
carry sediment to
ocean
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11. Emerging Shorelines
 Shorelines above current sea level
 Marine terraces – flat platforms backed by cliffs
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12. Submerging Shorelines
 Shoreline below current sea level
 Features include
 Drowned beaches
 Submerged dune topography
 Drowned river valleys (estuaries)
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13. Changing Sea Level
Two major processes can change sea level:
 Local tectonic processes
 Global (eustatic) changes in sea level
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14. 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
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15. 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
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16. Eustatic Changes in Sea Level
Some Mechanisms
 Ice ages lock seawater up in ice (glaciation) – sea level
goes down
 Ice melting after an ice age (deglaciation) – sea level
rises
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18. 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).
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19. 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.
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