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.