1. The Movement of Ocean Water
Chapter 20

2. Sections
Currents
Waves
Tides

3. Currents Ocean currents are streamlike movements of water.
When these movements occur at or near the surface of the ocean, they are called surface currents.

4. Currents
Winds blowing across the Earth’s surface create surface currents in the ocean.
Near the equator, they flow east to west. But near the poles, they flow west to east.

5. Currents
Earth’s rotation causes surface currents to move along curved paths in stead of straight lines.
This is known as the Coriolis effect.

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

7. Currents
Surface currents are also affected by the temperature of the water in which they form.
Warm-water currents carry warm water to other parts of the ocean … and cool-water currents carry cool water.

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

10. Currents
Upwelling is when cold, nutrient-rich water from the deep ocean rises to the surface and replaces warm surface water.
The change in location of warm and cool water in the Pacific is known as El Nino.

11. Currents
Deep currents are streamlike movements of ocean water far below the surface.
These currents form in parts of the ocean where water density increases.

12. Currents
Lower temperatures and higher salinity cause ocean water to become more dense.
Formation of ice and evaporation raise the salinity of water.

13. Waves
Most waves form as the wind blows across the water’s surface and transfers energy to the water.
As the energy moves through the water – so do the waves.

14. Waves Crest is the highest point. Trough is the lowest point.
Wavelength is the distance between two crests or troughs.
Wave height is the vertical distance between crest and trough.

16. Waves
Wave period is the time between the passage of two wave crests (or troughs) at a fixed point. =
wavelength (m)
wave speed (m/s)
wave period (s)

17. Waves
As waves approach the shore, they increase in height and eventually crash as breakers.
Water moves back to the ocean under the waves in a current called an undertow.
Waves hitting the shore at an angle cause a current along the shoreline called a longshore current.

18. Waves There are two types of waves in the open ocean:
Whitecaps break in the open ocean before they get close to shore.
Swells are rolling waves that move steadily across the ocean.

20. Waves
Tsunamis are waves that form when a large volume of ocean water is suddenly moved up or down.
They can be caused by earthquakes, volcanic eruptions, landslides, underwater explosions, or the impact of a meteor or comet.
The highest recorded was 64m high!

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

26. Tides Tides are daily changes in the level of ocean water.
The moon’s pull is strongest on the part of the Earth directly facing the moon.
Water on the opposite side of Earth bulges because of the rotation of the Earth.

27. Tides When the ocean bulges – it is called a high tide.
Water is drawn away from the area between the high tides – causing a low tide.
The moon revolves around the Earth more slowly than the Earth turns – so high tide is at a different time every day.

28. Tides
Lunar phases or the changes in the moon’s appearance, are connected to the tides.
The lunar cycle of these changes lasts about 28 days.
The sun also affects tides, but is less powerful than the moon because of its distance from Earth.

29. Tides
Tides with the largest range are called spring tides and happen when the sun, Earth, and moon line up with one another.
Spring tides occur with every new and full moon, about every 14 days.
Tides with the smallest range are called neap tides and happen when the sun, Earth, and moon for a 90° angle.