UNIT SEVEN: Earth’s Water

2. UNIT SEVEN: Earth’s Water • Chapter 21 Water and Solutions • Chapter 22 Water Systems • Chapter 23 How Water Shapes the Land

4. Chapter Twenty-Two: Water Systems • 22.1 Water on Earth’s Surface • 22.2 The Water Cycle • 22.3 Oceans

5. Chapter 22.3 Learning Goals • Discuss the effects of temperature and salinity on Earth’s oceans. • Distinguish features of the ocean floor. • Compare and contrast the effects of surface currents and deep ocean currents.

6. 22.3 Oceans • Ocean water is about 3.5 percent salt. • The word salinity is a measure of the dissolved salts in water. • Most of the salt in ocean water is sodium chloride.

7. 22.3 Oceans • In some places, special ponds called salt evaporation pondsharvest salt from the ocean.

8. 22.3 Oceans The salt in the oceans comes from: • minerals in the ocean floor, • gases released by volcanoes, and • rivers that carry dissolved minerals out to sea.

9. Can you name Earth’s five oceans?

10. 22.3 Importance of oceans • Oceans are an important source of water for the water cycle. • Oceans spread energy and heat from the hot equator to the colder poles. • Phytoplankton produce most of the oxygen in the atmosphere.

11. 22.3 Oceans and Earth’s climate • The oceans are able to store heat energy. • The water on Earth prevents the planet from getting too hot or too cold.

12. 22.3 Oceans and Earth’s climate • The climates on the coastline are milder than they are inland because ocean-warmed air masses move over the oceans toward the land.

13. 22.3 Oceans and Earth’s climate • The climates on coastlines are milder than they are inland because ocean-warmed wind and air masses move over the oceans toward the land.

14. 22.3 Surface currents and gyres • The Sun’s unequal heating of Earth and the Coriolis effect cause permanent global wind patterns. • Surface ocean currents to form large rotating systems called gyres.

15. 22.3 Surface currents and gyres • One well-known current is the Gulf Stream. • Europe has mild winters due to both prevailing westerlies and the heat energy of the Gulf Stream.

16. 22.3 Deep ocean currents • Deep ocean currents move below the surface of the ocean. • They are slower than surface ocean currents.

17. 22.3 The ocean floor • Many of the important features of the oceans are hidden in deep water. • The continental margin is the region around continents that includes the: • continental shelf, • continental slope, and • continental rise.

18. 22.3 The continental shelf • Sand drifting down the steep face of a continental shelf cuts into the shelf just like streams cut into valleys.

19. 22.3 Features of the ocean floor • Maps can show the location of the continental shelf. • The true ocean floor is called the abyssal plain. • It is flat and smooth because a thick layer of sediment covers its features.

20. 22.3 The deep ocean floor • A barrier islandis a low, sandy island that lies parallel to the shoreline. • A bankis a low, flat region on the continental shelf. • A seamountis a steep-sided mountain that rises from the ocean floor.

21. 22.3 The deep ocean floor • A guyotis a seamount that has eroded so that it has a flat top and is underwater. • Mid-ocean ridgesmark places where two tectonic plates are separating and new ocean crust is being made. • Deep-ocean trenchesare the deepest parts of the ocean.

23. Investigation 22C Global Winds and Ocean Currents • Key Question: • How do temperature and salinity cause ocean layering?

24. Rip Currents • More than 80% of water rescues performed by surf beach lifeguards are due to rip currents. • Rip currents are sometimes called riptides, or undertow. Learn why these two terms are misleading.