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Vocabulary Review Summary of Key Ideas 23.1 To determine the shape and composition of the ocean floor, scientists use techniques such as echo sounding, sediment sampling, and satellite observation. 23.2 A continental margin (the underwater edge of a continent) can be active or passive, depending where it lies in relation to a subduction zone or transform fault. 23.3 The ocean basin’s topography varies widely and includes features such as abyssal plains and hills, deep-ocean trenches, and mid-ocean ridges. 23.4 Ocean-floor sediments vary in Write the term from the key vocabulary list that best completes the sentence. 1. A precision depth recorder uses the technique of ? to determine ocean depth. 2. The continental shelf extends from the shoreline ? to the , where water depth begins to increase rapidly. 3. The margin where an oceanic plate is subducting ? under a continental plate is called . 4. Composed of ocean-floor sediments, ? a(n) stretches out from the continental rise and is the flattest of all Earth’s surfaces. 5. Oozes are the decomposed remains of marine ? protists and animals, also called . Concept Review 6. In what ways is core sampling useful to our understanding of Earth and its oceans? composition. Scientists classify each sediment based on where it originated. 7. Is the continental rise part of the ocean basin, or part of a continent? What about the continental shelf? the continental slope? KEY VOCABULARY 8. Most of the sediments that compose the abyssal plain originated on continents. Describe how the sedimentary materials could have moved from land to the deep-ocean floor. abyssal hill (p. 517) fracture zone (p. 520) abyssal plain (p. 517) guyot (p. 520) active continental hydrogenous margin (p. 515) biogenous sediments sediments (p. 525) island arc (p. 518) 9. Explain two possible origins of large submarine canyons. continental margin (p. 514) passive continental 10. Why are deep-ocean trenches such common sites for earthquakes and volcanic eruptions? continental rise (p. 514) 11. How do mid-ocean ridges form? (p. 524) mid-ocean ridge (p. 519) margin (p. 515) continental shelf (p. 514) seamount (p. 520) continental slope (p. 514) submarine canyon (p. 515) coral atoll (p. 521) terrigenous sediments core sampling (p. 511) deep-sea trench (p. 518) (p. 523) turbidity current (p. 516) echo sounding (p. 510) 12. How can a coral atoll be attached to the ocean floor when corals cannot live (or, therefore, form reefs) in the deep ocean? 13. What is the difference between an ooze and other sediments? 14. Are you more likely to find a deep-ocean trench along an active continental margin or along a passive continental margin? Sketch and label a diagram to explain your answer. 528 Unit 6 Earth’s Oceans