Ocean Waves Ocean Waves

Text Book Page # 358 - 365 Text Book Page # 358 - 365

WavesWaves•A A WaveWave is a is a rhythmicrhythmic movementmovement

that carries that carries energyenergy through through matter or space.matter or space.

•In oceans, waves move through In oceans, waves move through seawater.seawater.

•A water wave A water wave is the movement of is the movement of energy through a body of water.energy through a body of water.

WavesWaves

Caused byCaused by::

•WindWind

•EarthquakesEarthquakes

Most waves form when winds blowing across the water’s surface transmit their energy to the water.

Wave size depends on the strength of the wind, and length of the time it blows.

The wave’s energy moves, but the water mostly stays at one place. Individual water molecules move up and down but they do not move forward or backward.

Water Motion• As a wave passes, water particles moves in circular motion. • Deeper water particles moves in a smaller circles than those

near the surface.• The wind affects the water at the surface than it affects the

deep water. • Below a certain depth, the water does not move at all as the

wave passes.

Wavelength

Wave Height

Crest

Trough

Still Water

Wave Parts

Parts of a WaveParts of a Wave•CrestCrest – – The highest point on a

wave.

•Trough Trough – – The lowest point on a wave.

•Wave HeightWave Height – – The vertical distance from the crest of a wave to the trough.

•WavelengthWavelength – – The horizontal distance between the crest of one wave and the crest of next wave.

Waves in water Waves in water 1. In 1. In deep waterdeep water, waves usually travel as , waves usually travel as long, and low waves called long, and low waves called swells.swells.

How waves changes near How waves changes near shore?shore?2. Friction 2. Friction with the ocean floor causes with the ocean floor causes waves to slow down in the shallow water waves to slow down in the shallow water near the shore.near the shore.

Wavelength decreases

How waves breaks against the How waves breaks against the shore?shore?3. When the water reaches certain height, 3. When the water reaches certain height, the the crest outruns the trough and the crest collapsescrest outruns the trough and the crest collapses. 4. . 4. The waves breaks onto the shore, forming The waves breaks onto the shore, forming surfsurf..

Feeling UndertowFeeling Undertow

The water that had rushed up the beach flows back out to sea. This pull is called an undertow carries shells, seaweeds, and sand away from the beach.

TsunamisTsunamis are caused by an are caused by an earthquake beneath the ocean floor. earthquake beneath the ocean floor.

The abrupt movement of ocean floor sends The abrupt movement of ocean floor sends pulses of energy through water above it.pulses of energy through water above it.

20 m

When tsunami reach the coast, they can be When tsunami reach the coast, they can be as devastating as an earthquake on land, as devastating as an earthquake on land, smashing buildings and bridges.smashing buildings and bridges.

Longshore Drift and Rip Currents Longshore Drift and Rip Currents

Longshore Drift – The movement of water and sediment down a beach caused by waves coming in to shore at an angle.

Rip current – A rush of water that flows rapidly back to sea through a narrow opening in a sandbar. •Rip current can take a swimmer out into deep water.

Waves and Beach Erosion - Waves and Beach Erosion - Waves Waves shapes a beach by eroding a shore in some shapes a beach by eroding a shore in some places and building up in others.places and building up in others. Barrier

Beaches •Long sand deposits form parallel to the shore.

•Separated from the mainland by a shallow lagoon.

•Natural landform that protects shorelines from wave action occurs along low-lying beaches.

Beach ErosionBeach ErosionSand Dunes – •Natural landform

•Reduces beach erosion

•Strong roots of dune plants, such as beach grass and sea oats, hold the sand in its place.

Groins – •A wall made of rocks and concrete that is built outward (perpendicular) from a beach.

•Reduces beach erosion