Chapter 9, Section 3
Ocean Shoreline
Where land meets the ocean. Surface waves, tides, and currents
cause shorelines to constantly change.
Shoreline Forces
There are 3 major shoreline forces: Waves Currents Tides
Waves Caused by winds blowing across the water.
Break rocks into tiny pieces.Can erode and move large
amounts of material in a short amount of time.
Currents Longshore current Formed when waves collide with the
shore at a slight angle. Causes water to run parallel to the
shore. Act like rivers of sand in the ocean.
Carry many metric tons of loose sediment.
Cause abrasion.
Tides Create currents that move at right angles to the shore. Called tidal currents
Move sediment into deeper waters.
Bring new sediment to the shore.
Features of Rocky Shorelines
Have rocks and cliffsAbout 14,000 waves crash onto
the shore each day. As waves crash into the cliffs, the rock
is worn away. Rock fragments are ground up by waves
and transported as sediment by longshore currents.
Softer rocks erode quicker than harder rocks, leaving islands of rock in the water.
Beaches Deposits of sediment that are parallel to the shore.
Made of different materials. Quartz and shell fragments are
common. Hawaii has black basalt beaches and
green olivine beaches.Grains range in size from .06 mm
to 2 mm in diameter.Grains tend to be smooth from
collisions with other grains.
Erosion and Deposition
Storms and wind cause waves that erode sediments.
These sediments are later deposited as features such as barrier islands, spits, and sandbars.
Barrier Islands
Sand deposits that lay parallel to the shore but are separated from the mainland.
Start as underwater sand ridges formed by breaking waves.
When the barrier island becomes big enough, loose sand is blown into dunes.
Have a life-time from a few years to a few centuries.
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