The Movement The Movement of Ocean Waterof Ocean Water

Chapter 20Chapter 20

SectionsSections

•CurrentsCurrents•WavesWaves•TidesTides

CurrentsCurrents•Ocean currentsOcean currents are streamlike are streamlike movements of water.movements of water.

•When these movements occur When these movements occur at or near the surface of the at or near the surface of the ocean, they are called ocean, they are called surface surface currents.currents.

CurrentsCurrents•Winds blowing across the Winds blowing across the Earth’s surface create surface Earth’s surface create surface currents in the ocean.currents in the ocean.

•Near the equator, they flow Near the equator, they flow east to west. But near the east to west. But near the poles, they flow west to east.poles, they flow west to east.

CurrentsCurrents•Earth’s rotation causes Earth’s rotation causes surface currents to move surface currents to move along curved paths in stead along curved paths in stead of straight lines.of straight lines.

•This is known as the This is known as the Coriolis effect.Coriolis effect.

CurrentsCurrents

•Continents also cause the Continents also cause the surface currents to deflect, surface currents to deflect, or change direction.or change direction.

CurrentsCurrents•Surface currents are also Surface currents are also affected by the temperature affected by the temperature of the water in which they of the water in which they form.form.

•Warm-water currents carry Warm-water currents carry warm water to other parts of warm water to other parts of the ocean … and cool-water the ocean … and cool-water currents carry cool water.currents carry cool water.

CurrentsCurrents

•The temperature of surface The temperature of surface currents affect the climate currents affect the climate of land near the area where of land near the area where they flow.they flow.

CurrentsCurrents•UpwellingUpwelling is when cold, is when cold,

nutrient-rich water from the nutrient-rich water from the deep ocean rises to the deep ocean rises to the surface and replaces warm surface and replaces warm surface water.surface water.

•The change in location of The change in location of warm and cool water in the warm and cool water in the Pacific is known as Pacific is known as El Nino.El Nino.

CurrentsCurrents•Deep currentsDeep currents are are streamlike movements of streamlike movements of ocean water far below the ocean water far below the surface.surface.

•These currents form in These currents form in parts of the ocean where parts of the ocean where water density increases.water density increases.

CurrentsCurrents•Lower temperatures and Lower temperatures and higher salinity cause ocean higher salinity cause ocean water to become more dense.water to become more dense.

•Formation of ice and Formation of ice and evaporation raise the salinity evaporation raise the salinity of water.of water.

WavesWaves•Most waves form as the wind Most waves form as the wind blows across the water’s blows across the water’s surface and transfers energy surface and transfers energy to the water.to the water.

•As the energy moves As the energy moves through the water – so do through the water – so do the waves.the waves.

WavesWaves•CrestCrest is the highest point. is the highest point.

•TroughTrough is the lowest point. is the lowest point.

•WavelengthWavelength is the distance is the distance between two crests or troughs.between two crests or troughs.

•Wave heightWave height is the vertical is the vertical distance between crest and distance between crest and trough.trough.

•Wave periodWave period is the time is the time between the passage of two between the passage of two wave crests (or troughs) at a wave crests (or troughs) at a fixed point.fixed point.

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WavesWaves

wavelength (m)wave period (s) wave speed (m/s)

WavesWaves•As waves approach the shore, they As waves approach the shore, they

increase in height and eventually increase in height and eventually crash as crash as breakers.breakers.

•Water moves back to the ocean Water moves back to the ocean under the waves in a current called under the waves in a current called an an undertow.undertow.

•Waves hitting the shore at an angle Waves hitting the shore at an angle cause a current along the shoreline cause a current along the shoreline called a called a longshore current.longshore current.

WavesWaves•There are two types of waves There are two types of waves

in the open ocean:in the open ocean:

•WhitecapsWhitecaps break in the open break in the open ocean before they get close to ocean before they get close to shore.shore.

•SwellsSwells are rolling waves that are rolling waves that move steadily across the move steadily across the ocean.ocean.

WavesWaves•TsunamisTsunamis are waves that form when a are waves that form when a

large volume of ocean water is large volume of ocean water is suddenly moved up or down.suddenly moved up or down.

•They can be caused by earthquakes, They can be caused by earthquakes, volcanic eruptions, landslides, volcanic eruptions, landslides, underwater explosions, or the impact underwater explosions, or the impact of a meteor or comet.of a meteor or comet.

•The highest recorded was 64m high!The highest recorded was 64m high!

WavesWaves

•A A storm surgestorm surge is a local rise in is a local rise in sea level near the shore that is sea level near the shore that is caused mainly by strong winds caused mainly by strong winds from a storm, such as a from a storm, such as a hurricane.hurricane.

TidesTides•TidesTides are daily changes in the are daily changes in the

level of ocean water.level of ocean water.

•The moon’s pull is strongest on The moon’s pull is strongest on the part of the Earth directly the part of the Earth directly facing the moon.facing the moon.

•Water on the opposite side of Water on the opposite side of Earth bulges because of the Earth bulges because of the rotation of the Earth.rotation of the Earth.

TidesTides•When the ocean bulges – it is called When the ocean bulges – it is called

a high tide.a high tide.

•Water is drawn away from the area Water is drawn away from the area between the high tides – causing a between the high tides – causing a low tide.low tide.

•The moon revolves around the Earth The moon revolves around the Earth more slowly than the Earth turns – so more slowly than the Earth turns – so high tide is at a different time every high tide is at a different time every day.day.

TidesTides•Lunar phasesLunar phases or the changes in the or the changes in the

moon’s appearance, are connected moon’s appearance, are connected to the tides.to the tides.

•The The lunar cyclelunar cycle of these changes of these changes lasts about 28 days.lasts about 28 days.

•The sun also affects tides, but is less The sun also affects tides, but is less powerful than the moon because of powerful than the moon because of its distance from Earth.its distance from Earth.

TidesTides•Tides with the largest range are called Tides with the largest range are called

spring tidesspring tides and happen when the sun, and happen when the sun, Earth, and moon line up with one Earth, and moon line up with one another.another.

•Spring tides occur with every new and Spring tides occur with every new and full moon, about every 14 days.full moon, about every 14 days.

•Tides with the smallest range are Tides with the smallest range are called called neap tidesneap tides and happen when the and happen when the sun, Earth, and moon for a 90sun, Earth, and moon for a 90° angle.° angle.