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Deep-Ocean Basins Chapter23 The Ocean Basins ChapterCh t Outline Outli ne 1 ● The Water Planet Divisions of the Global Ocean Exploration of the Ocean 2 ● Features of the Ocean Floor Continental Margins Deep-Ocean Basins 3 ● Ocean-Floor Sediments Sources of Deep Ocean– Basin Sediments Physical Classification of Sediments Why It Matters Oceans cover more than 70 percent of Earth’s surface. Oceans interact with the atmosphere to influence weather and climate. Exploring and analyzing data about the chemistry of ocean water, the geology of the ocean floor, marine ecosystems, and the physics of water movement is critical to understanding natural processes on Earth. 634 Chapter 23 hhq10sena_obacho.inddq10sena_obacho.indd 663434 PDF 88/1/08/1/08 11:09:46:09:46 PPMM Inquiry Lab 20 min Sink or Float? Fill the bottom half of 3-L soda bottle with water to within about 3 inches from the top and place it on a plastic or metal tray to catch any spills. Using small (3-oz) plastic cups, with some paper clips and metal nuts for ballast, see if you can get a cup to sink with air still trapped inside, simulating a submersible. You may need something pointed to make holes in the cups. Questions to Get You Started 1. What is buoyancy and why is it so important for maritime travel? 2. Compare techniques for sinking the cup. Does one method consistently work better than others? 3. What challenges do engineers face when designing submersibles? 635 hhq10sena_obacho.inddq10sena_obacho.indd 663535 PDF 88/1/08/1/08 11:09:58:09:58 PPMM These reading tools will help you learn the material in this chapter. Science Terms Classification Everyday Words Used in Science Many Classifying Sediments Classification is a words used in science are familiar words tool for organizing objects and ideas by from everyday speech. However, the grouping them into categories. Groups are meanings of these everyday words are classified by defining characteristics. For often different from their meanings in example, the table below shows how scientific contexts. sediments can be classified by their composition. Your Turn Before you read this chapter, write down an informal definition of what Your Turn As you read the chapter, the word margin means to you. As you complete a table like the one shown here come across this word in the chapter, write for the three types of sediments described the scientific definition next to your in Section 3. informal definition. For each definition, write a sentence that uses the word margin Type of Sediment Characteristics correctly. Inorganic Carried from land to ocean by rivers, wind, and icebergs Biogenic Chemical Graphic Organizers Spider Maps Spider maps show how Your Turn As you read Section 2, use a details are organized into categories, which spider map to organize the information that in turn are related to a main idea. To make a you learn about features of the ocean floor. spider map, follow the steps. 1 Write a main topic title, and draw an oval Ocean Floor Features around it. 2 From the oval, draw legs. Each leg Continental Margin Deep Ocean represents a category of the main topic. 3 From each leg, draw horizontal lines. Write details about each category on these lines. For more information on how to use these and other tools, see Appendix A. 636 Chapter 23 The Ocean Basins hhq10sena_obatoolx.inddq10sena_obatoolx.indd 663636 PDF 88/1/08/1/08 11:08:04:08:04 PPMM SECTION 1 The Water Planet Keyey Ideasdeas Keyey TTermseesrms WhyWhy IItt MattersMatte rs ❯ Name the major divisions of the global ocean. global ocean New ways to explore the ❯ Describe how oceanographers study the ocean. sea cold, dark ocean depths ❯ have revealed to us the Explain how sonar works. oceanography bizarre life forms that sonar thrive there. Nearly three-quarters of Earth’s surface lies beneath a body of salt water called the ggloballobal oocean.cean. No other known planet has a similar covering of liquid water. Only Earth can be called the water planet. The global ocean contains more than 97% of all of the water on or near Earth’s surface. Although the ocean is the most prominent feature of Earth’s surface, the ocean is only about 1/4,000 of Earth’s total mass and only 1/800 of Earth’s total volume. Divisions of the Global Ocean As shown in Figure 1, the global ocean is divided into five major oceans. These major oceans are the Atlantic, Pacific, Indian, Arctic, and Southern Oceans. Each ocean has special characteris- tics. The Pacific Ocean is the largest ocean on Earth’s surface. It global ocean the body of salt contains more than one-half of the ocean water on Earth. With an water that covers nearly three- average depth of 4.3 km, the Pacific Ocean is also the deepest fourths of Earth’s surface sea a large, commonly saline ocean. The next largest ocean is the Atlantic Ocean. The Atlantic body of water that is smaller Ocean has an average depth of 3.9 km. The Indian Ocean is the than an ocean and that may be third-largest ocean and has an average depth of 3.9 km. The partially or completely Southern Ocean is the fourth-largest ocean and extends from the surrounded by land coast of Antarctica to 60°S latitude. The Arctic Ocean is the small- est ocean, and it surrounds the North Pole. A sseaea is a body of water that is ARCTIC OCEAN smaller than an ocean and that Bering may be partially surrounded Sea Baltic Sea North by land. Examples of Sea Sea of major seas include the Japan Mediterranean N South N Sea A Mediterranean Sea, the China A Caribbean Sea Arabian E Sea E Sea C Caribbean Sea, and the C Equator O INDIAN O C OCEAN C I South China Sea. I T F Timor Sea I N C A A L P T A Figure 1 The global ocean is divided into oceans and seas. How many oceans are on Earth? SOUTHERN OCEAN 637 hhq10sena_obasec1.inddq10sena_obasec1.indd 663737 PDF 88/19/08/19/08 88:23:14:23:14 AAMM Exploration of the Ocean The study of the physical and geological characteristics, chemi- oceanography the scientific cal composition, and life-forms of the ocean is called ooceanography.ceanography. study of the ocean, including the Although some ancient civilizations studied the ocean, modern properties and movements of ocean water, the characteristics oceanography did not begin until the 1850s. of the ocean floor, and the organisms that live in the ocean The Birth of Oceanography An American naval officer named Matthew F. Maury used records from navy ships to learn about ocean currents, winds, depths, and weather conditions. In 1855, he published these obser- vations as one of the first textbooks about the oceans. Then, from 1872 to 1876, a team of scientists aboard the British Navy ship HMS www.scilinks.org Challenger crossed the Atlantic, Indian, and Pacific Oceans. The sci- Topic: The Oceans Code: HQX1069 entists measured water temperatures at great depths and collected samples of ocean water, sediments, and thousands of marine organisms. The voyages of the HMS Challenger laid the foundation Academic Vocabulary for the modern science of oceanography. research (REE SUHRCH) a careful search Today, many ships perform oceanographic research. In the for and study of information 1990s and in the beginning of the 21st century, the research ship JOIDES Resolution was the world’s largest and most sophisticated scientific drilling ship. Samples drilled by JOIDES Resolution, shown in Figure 2, provide scientists with valuable information about plate tectonics and the ocean floor. The Japanese ship CHIKYU, which is operated by the Integrated Ocean Drilling Program, is one of the most advanced drilling ships now in use. List three characteristics of the ocean that oceanographers study. (See Appendix G for answers to Reading Checks.) Figure 2 Reentry cones (above) are used so that core samples can later be taken from the same place on the ocean floor. Scientists aboard the research ship JOIDES Resolution (right) perform scientific studies of the ocean floor. 638 Chapter 23 The Ocean Basins hhq10sena_obasec1.inddq10sena_obasec1.indd 663838 22/23/09/23/09 99:42:09:42:09 AAMM Reflected sound waves Sound waves Classification from ship Classify each type of tool used to collect data from oceans, including records from ships, Keyword: HQXOBAF3 samples taken from ships, sonar, and submersibles, as surface Figure 3 Active sonar sends out a pulse of sound. The pulse, called a tools or deep-ocean tools. ping because of the way it sounds, reflects when it strikes a solid object. Sonar Oceanographic research ships are often equipped with sonar. SSonaronar is a system that uses acoustic signals and returned echoes to sonar sound navigation and determine the location of objects or to communicate. Sonar is an ranging, a system that uses acoustic signals and returned acronym for sound navigation and ranging. A sonar transmitter echoes to determine the sends out a continuous series of sound waves from a ship to the location of objects or to ocean floor, as shown in Figure 3. The sound waves travel at about communicate 1,500 m/s through sea water and bounce off the solid ocean floor. The waves reflect back to a receiver. Scientists measure the time that the sound waves take to travel from the transmitter, to the ocean floor, and to the receiver in order to calculate the depth of the ocean floor. Scientists then use this information to make maps and profiles of the ocean floor.
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