518-S1-MSS08 1/18/07 2:15 AM Page 540 S6E3. Students will recognize the significant role of water in Earth’s processes. S6E5. Students will investigate the scientific view of how Earth’s surface is formed. Also covers: S6CS1–6, 8–9 Oceanography Many organisms, including humans, depend on the ocean for their survival. SECTION 1 The Seafloor Main Idea Ocean basins, which are low areas of Earth that are filled with water, have many different features. SECTION 2 Life in the Ocean Main Idea Nearly all of the energy used by organisms in the ocean ultimately comes from the Sun. SECTION 3 Ocean Pollution Main Idea Pollutants from land eventually will reach the ocean. Marine Life This inch-long jelly drifts with ocean currents and uses stinging tentacles to capture small prey. Through a chemical process called bioluminescence it is able to produce light and glow in the dark. Science Journal Describe characteristics of three marine organisms you are familiar with. 540 (bkgd.)Bill Curtsinger/Getty Images Start-Up Activities The Seafloor Make the follow- ing Foldable to help you identify the features of the seafloor. How deep is the ocean? Sonar is used to measure ocean depth. You STEP 1 Fold a sheet of paper in half length- will model sonar in this lab. wise. Make the back edge about 1.25 cm longer than the front edge. 1. With one person holding each end, stretch a spring until it is taut. Mea- STEP 2 Fold in half, then fold sure the distance in half again to make three folds. between the ends. 2. Pinch two coils together. When the spring STEP 3 Unfold and cut only the top layer along is steady, release the coils to create a wave. the three folds to make four tabs. 3. Record the time it takes the wave to travel back and forth five times. Divide this number by five to calculate the time of one round trip. 4. Calculate the speed of the wave by multi- plying the distance by two and dividing STEP 4 Label the tabs as shown. this number by the time. 5. Move closer to your partner. Take in coils Abyssal Land Shelf Slope Plain to keep the spring at the same tension. Repeat steps 2 and 3. Find Main Ideas As you read the chapter, draw 6. Calculate the new distance by multiplying seafloor features on the front of the tabs and the new time by the speed from step 4, write information about them under the tabs. and then dividing this number by two. 7. Think Critically Write a paragraph in your Science Journal that describes how Preview this chapter’s content and activities at this lab models sonar. earth.msscience.com 541541 (bkgd.)Bill Curtsinger/Getty Images, (inset)Mark Burnett Learn It! Asking questions helps you to understand what you read. As you read, think about the questions you’d like answered. Often you can find the answer in the next paragraph or section. Learn to ask good questions by asking who, what, when, where, why, and how. Practice It! Read the following passage from Section 2. An estuary is an area where the mouth of a river opens into an ocean. … Rivers bring nutrients to estuaries. Areas with many nutrients usually have many phytoplankton, which form the base of the food chain. … Estuaries are an important habitat to many marine organisms. Newly hatched fish, shrimps, crabs, and other animals enter estu- aries as microscopic organisms and remain there until adulthood. For these vulnerable animals, fewer predators and more food are found in estuaries. —from page 556 Here are some questions you might ask about this paragraph: • What is an estuary? • What are phytoplankton? • Why are estuaries important? Apply It! As you read the chapter, look for answers to section headings that are in the form of questions. 542 A CHAPTER 19 Oceanography stions ate que rself.Cre Test you find answers and then read to Use this to focus on the main ideas as you read the chapter. to your own questions. Before you read the chapter, respond to the statements below on your worksheet or on a numbered sheet of paper. • Write an A if you agree with the statement. • Write a D if you disagree with the statement. After you read the chapter, look back to this page to see if you’ve changed your mind about any of the statements. • If any of your answers changed, explain why. • Change any false statements into true statements. • Use your revised statements as a study guide. Before You Read Statement After You Read A or D A or D 1 The continental shelf is always wider than 100 km. 2 A mid-ocean ridge is the area in an ocean basin where ocean floor is formed. 3 Mid-ocean ridges can be found at the bottom of all ocean basins. 4 Most ocean trenches are found in the Pacific Basin. 5 Chemosynthesis requires sunlight to change car- Print out a worksheet bon dioxide and water into sugar and oxygen. of this page at earth.msscience.com 6 Most marine organisms live in the waters of the deep ocean or on the floor of the abyssal plains. 7 An estuary is an area where the mouth of a river opens into an ocean. 8 Air pollution does not affect ocean pollution. 9 Less than 5 percent of oil pollution that reaches the ocean comes from land. 10 Today, there is not a single area of the ocean that is not polluted in some way. 542 B 518-S1-MSS08 1/18/07 2:19 AM Page 542 S6E3d. Explain the causes of waves, currents, and tides. S6E5f. Explain the effects of physical processes (plate tectonics, erosion, deposition, volcanic eruptions, gravity) on geological features including oceans (composition, currents, and tides). Also covers: S6CS5b, 9d The Seafloor The Ocean Basins Imagine yourself driving a deep-sea submersible along the ocean floor. Surrounded by cold, black water, the lights of your vessel reflect off of what looks like a mountain range ahead. As I Differentiate between a conti- nental shelf and a continental you continue, you find a huge opening in the seafloor—so deep slope. you can’t even see the bottom. What other ocean floor features I Describe a mid-ocean ridge, an can you find in Figure 1? abyssal plain, and an ocean Ocean basins, which are low areas of Earth that are filled trench. I Identify the mineral resources with water, have many different features. Beginning at the ocean found on the continental shelf shoreline is the continental shelf. The continental shelf is the and in the deep ocean. gradually sloping end of a continent that extends under the ocean. On some coasts, the continental shelf extends a long dis- tance. For instance, on North America’s Atlantic and Gulf coasts, Oceans cover nearly three fourths of it extends 100 km to 350 km into the sea. On the Pacific Coast, Earth’s surface. where the coastal range mountains are close to the shore, the shelf is only 10 km to 30 km wide. The ocean covering the con- Review Vocabulary magma: hot, melted rock tinental shelf can be as deep as 350 m. beneath Earth’s surface New Vocabulary • continental shelf • continental slope • abyssal plain • mid-ocean ridge • trench Kelvin Seamount e g Mariana id R Trench ic t n Hatteras a l Abyssal t A Plain - d Figure 1 This map shows fea- i tures of the ocean basins. Locate a Puerto Rico M Trench trench and a mid-ocean ridge. Demerara P e Abyssal M r u Plain i d - C - A h M i t l l i e d a T - n I r n e t d n i i c c a h R n O id cea ge ge n Rid 542 CHAPTER 19 Oceanography The Floor of the Oceans by Bruce C. Heezen and Marie Tharp, © 1977 by Marie Tharp. Reproduced by permission of Marie Tharp Sea surface Abyssal plain Continental Volcanic island shelf 200 m Continental slope Seamount 4,000 m 6,000 m Mid-ocean ridge Oceanic trench 10,000 m Figure 2 shows that beyond the shelf, the ocean floor drops Figure 2 Ocean basin features more steeply, forming the continental slope. The continental are continuous from shore to slope extends from the outer edge of the continental shelf down shore. (Features in this diagram to the ocean floor. Beyond the continental slope lie the trenches, are not to scale.) valleys, plains, mountains, and ridges of the ocean basin. Describe where the continental In the deep ocean, sediment, derived mostly from land, set- shelf ends and the continental tles constantly on the ocean floor. These deposits fill in valleys slope begins. and create flat seafloor areas called abyssal (uh BIH sul) plains. Abyssal plains are from 4,000 m to 6,000 m below the ocean surface. Can you locate the abyssal plain shown in Figure 2? In the Atlantic Ocean, areas of extremely flat abyssal plains can be large. One example is the Canary Aleutian Abyssal Plain Abyssal Plain, which has an area of Topic: Ocean Basins 2 Visit earth.msscience.com for Web Hatteras approximately 900,000 km .Other Abyssal abyssal plains found in the Atlantic links to information about ocean Plain Ocean include the Hatteras and basins. Demerara Abyssal Plains, both shown Activity Find five fun facts in Figure 1. Some areas of abyssal about ocean basins, such as the plains have small hills and seamounts.