Transcript Ocean Shoreline - Choteau Schools

Chapter 9, Section 3
The Shore

Ocean
Shoreline

Where land meets the ocean.
 Surface waves, tides, and currents
cause shorelines to constantly
change.
The Shore

Shoreline
Forces

There are 3 major shoreline
forces:
 Waves
 Currents
 Tides
The Shore

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.
The Shore

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.
The Shore

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.

Rocky Shorelines

Features of
Rocky
Shorelines


Have rocks and cliffs
About 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.
Sandy Beaches

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.
Sand Erosion and Deposition

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.
Sand Erosion and Deposition

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.
