ocean wave and current erosion or... whoa sally, this ocean has motion!

Ocean Wave and Current Ocean Wave and Current ErosionErosion

Or . . . Whoa Sally, this ocean has motion!

Wave MotionsWave Motions• Particles in a wave travel circular pathsParticles in a wave travel circular paths• The water in a deep-water wave does The water in a deep-water wave does

not move forwardnot move forward

The Highest Recorded Ocean The Highest Recorded Ocean WaveWave

When Waves Meet the ShoreWhen Waves Meet the Shore

When the beach interferes with wave When the beach interferes with wave motion, the wave steepens and the motion, the wave steepens and the top overtakes the bottom.top overtakes the bottom.

Kowabunga!Kowabunga!

Wave RefractionWave Refraction

• Waves change path when they reach Waves change path when they reach shallow watershallow water

• Wave energy is concentrated on Wave energy is concentrated on headlands and spread out in baysheadlands and spread out in bays

Shore ErosionShore Erosion

• Wave energy can Wave energy can carve out arches in carve out arches in the headlands.the headlands.

• Overtime a sea Overtime a sea stack is formed.stack is formed.

Rip TidesRip Tides• When waves break parallel to a beach, When waves break parallel to a beach,

rip currents or rip tides occur.rip currents or rip tides occur.

Longshore Current and Beach Longshore Current and Beach DriftDrift

• Most beach sand is Most beach sand is created by created by weathering and weathering and carried to coasts by carried to coasts by rivers.rivers.

• Beach sand moves Beach sand moves along the coast by along the coast by the longshore the longshore current and beach current and beach drift.drift.

Barrier IslandBarrier Island• Long, narrow islands of Long, narrow islands of sandsand and/or and/or gravelgravel

that are usually aligned parallel to the shore. that are usually aligned parallel to the shore.

Trying to save the beachTrying to save the beach

• Man has tried to Man has tried to save beaches by save beaches by building groins that building groins that retard the flow of retard the flow of sand with the sand with the longshore current.longshore current.

• These are of These are of limited success.limited success.

We foolishly build We foolishly build right on the beach.right on the beach.

In the long run, nothing is In the long run, nothing is as futile as trying to resist as futile as trying to resist shoreline change. Change shoreline change. Change

can be resisted for a can be resisted for a while, but when the water while, but when the water

wants something badly wants something badly enough, it will come in enough, it will come in

and take it. and take it.