Procedure Follow the steps below while taking notes in your science notebook. 1. Name and locate all of the continents. 2. Identify linear (straight-line) and arcuate (curved-line) features on the continents. Do not include rivers or coastlines. a. Identify the major mountain chains and trace them with your finger. b. Find linear lakes in Africa. 3. Move to the ocean. Name and locate the four major ocean basins (major oceans). a. Note that oceanographers often refer to the North Atlantic and the South Atlantic Oceans, even though they are both part of one major ocean basin. b. Remember that the Earth has only one interconnected ocean; however there are 4 major ocean basins. 4. Locate the following seas and gulfs: o Atlantic Ocean: Mediterranean Sea Caribbean Norwegian Sea Gulf of Mexico Overheads-1
o Indian Ocean: Red Sea Arabian Sea o Pacific Ocean: Gulf of California a. Note the linear nature of the Red Sea and the Gulf of California. 5. Identify a variety of linear and arcuate features on the ocean floor. List the different types of features in your science notebook (or on the chalkboard), and include several examples of each type. 6. Find Iceland. It sits on top of the Mid-Atlantic Ridge, a classic mid-ocean ridge. Mid-ocean ridges are underwater mountain chains. A rise is another term for a ridge. a. Find several other mid-ocean ridges. o Pacific Ocean: East Pacific Rise Juan de Fuca Ridge o Indian Ocean: Southwest Ridge Southeast Indian Ridge Carlsberg Ridge (Mid-Indian Ridge) b. What other type of seafloor feature is also found along midocean ridges? Overheads-2
c. Find the Hawaiian Ridge. How does it differ from mid-ocean ridges? d. Find the Ninety East Ridge in the Indian Ocean. Is it more like a mid-ocean ridge or the Hawaiian Ridge? 7. Trace the mid-ocean ridges with your finger, beginning at Iceland in the North Atlantic Ocean. See how far around the globe you can travel just by traveling along mid-ocean ridges. a. Compare this system of connected ridges to the seam of a baseball. (See if your teacher has a baseball to view.) 8. Examine the Pacific Ocean and locate several fracture zones. Find the following fracture zones: o Pacific Ocean: Eltanin Challenger o Atlantic Ocean: Gibbes Romanche Rio Grande o Indian Ocean: Owen Prince Edward 9. What is the geographic association between ridges and fracture zones? Overheads-3
10. (Optional) Using two different colors of transparency (erasable!) marker pens, draw the approximate locations of ridges and a few of the largest fracture zones on a globe. 11. Find several ocean floor trenches. As you locate each, trace them with your finger. a. Locate the following trenches: o Pacific Ocean: Aleutian Trench Kuril Trench Japan Trench Mariana Trench Philippine Trench Tonga Trench Peru-Chile Trench Middle America Trench o Atlantic Ocean: Puerto Rico Trench Cayman Trench South Sandwich Trench o Indian Ocean: Java Trench b. The Mariana Trench is the deepest spot on Earth at approximately 11 km (6.8 miles)! The Mariana Trench is deeper than the entire height (relief) of Mount Everest! c. Note that there is no trench off the California coast, but there is a small trench (the Juan de Fuca Trench) off the coast of Oregon and Washington states. Overheads-4
12. (Optional) Using a third color of transparency marker pen, draw the location of trenches on the globe. 13. Examine the Pacific Ocean again to find seamounts that are arranged in chains. Seamounts are volcanoes that originate on the seafloor (not on a continent). Some have grown so that they are above sea level, so we refer to them as volcanic islands, while others are below sea level and are called seamounts. a. Locate the following volcanic island chains and trace them on your map with your finger: o Pacific Ocean: Aleutian Islands Kuril Islands (southwest of Kamchatka Peninsula) Japan Philippine Islands 14. What is the geographic association between trenches and seamount (or volcanic island) chains? 15. Locate the following volcanic mountain chains (on the continents): o Andes Mountains, Sierra Madre (Central American), and the Cascade Mountains (in Oregon and Washington). 16. What is the association between volcanic mountain chains and trenches? 17. (Optional) Using a fourth color of transparency marker pen, draw the location of seamount chains on the globe. Overheads-5
18. Find the Hawaiian Islands. These islands are part of a long chain of seamounts that extends northwest, beyond the islands. Beginning at the big island of Hawaii, trace your finger along the chain. In what direction is your finger moving? What is the ridge called? a. Is this the same kind of ridge as a mid-ocean ridge? b. What occurs to the volcanic chain at approximately 170 E longitude? What is this feature called? c. Are there any trenches associated with either of these two seamount chains? Is the association similar to other seamount chains and trenches? d. Find the arcuate Louisville Ridge, northeast of New Zealand and trace its orientation from west to east. If you continue to move your finger in the same general arcuate eastward direction, what seafloor feature do you encounter that is also oriented similarly? e. Summarize your observations about seamount chains, volcanic island chains, volcanic mountain chains, trenches and fracture zones. Provide an example for each observation. 19. Now that you have explored the various types of seafloor features throughout three of the four major ocean basins, let s take a seafloor tour around the Pacific Ocean. Begin off the coast of Alaska, at the eastern end of the Aleutian Trench. What arcuate feature is just north of this trench? Overheads-6
a. With your finger, follow the Aleutian Trench westward until other linear or arcuate features are encountered. Trace the trenches all the way to New Zealand. b. What are the trenches you encountered along the way? Were there any other seafloor features associated with those trenches? c. As you head generally eastward from the Philippine region, you will find many broken segments of trenches, and a lot of volcanic islands. d. What is the name of the linear trench north of New Zealand? e. From New Zealand, travel south until you encounter the East Pacific Rise (EPR). Follow this mid-ocean ridge system eastward until you find a seafloor feature to follow that takes you to the edge of South America. What feature did you find? f. What feature can you now follow all along the coast of South America towards Central America? g. What seafloor feature do you encounter parallel to the coast of Central America? h. As you move toward North America, you will reconnect to the EPR as it zig-zags into the Gulf of California. The Gulf of California is a very linear sliver of ocean between Mexico and the very linear Baja Peninsula. The EPR appears to end as it runs into the North American continent at the northern tip of the Gulf of California. Overheads-7
20. At this point, you ve traveled nearly the entire perimeter of the Pacific Ocean basin by hopping from one seafloor feature to another. But you aren t finished yet (we just need to take a quick detour across California). a. From the northern end of the Gulf of California, move across southern California, past Los Angeles to San Francisco, then northward to the small Juan de Fuca Ridge off the coast of Oregon and Washington. This path is the trace of the San Andreas Fault. It is neither a ridge nor trench, but is actually a fracture zone that connects two ridge segments (the Gulf of California segment and the Juan de Fuca Ridge segment). b. It will be difficult to find a seafloor feature to connect the northern end of the Juan de Fuca Ridge to your starting point at the Aleutian Trench. So your tour has ended, but you have almost completed a circum-pacific journey! Overheads-8
21. Now you have completed your tour of the Pacific Ocean. On a separate piece of paper (or, using tracing paper) draw a map of the path you've just traveled, labeling the major features along the route. Use the following symbols to identify different seafloor features: 22. Now let s examine the Atlantic Ocean. Would you be able to take a similar circum-atlantic tour following seafloor features? a. Can you find seamount chains similar to the Hawaii, Nazca and Louisville Ridges of the Pacific Ocean? 23. Make a chart that compares the abundance of trenches, midocean ridges, fracture zones, volcanic island chains, and volcanic mountain chains of the Pacific and Atlantic Ocean basins. 24. Review the associations you ve observed among ridges, trenches, volcanic island chains, seamount chains and continental volcanic mountain chains. Overheads-9
Summarize your observations and discoveries by answering the questions that follow. Questions Use your observations of the seafloor features and the associations between and among these features to answer the following questions. Your teacher will provide information of how to format your answers. 1) What are the associations between or among the following seafloor features and continental feature? Describe the characteristics observed (including if the features exhibit linear and/or arcuate geometries) and, generally where they are found in each ocean. For each feature include any associated seafloor features and their geographic relationship. Expand your observations from step number 18e. For each association, provide and example. Mid-ocean ridges Fracture zones Trenches Volcanic island chains/seamount chains Volcanic mountain chains 2) How is the Hawaiian Ridge different from the East Pacific Rise? Identify a ridge in the Indian Ocean that is similar to the Hawaiian Ridge. How is this ridge similar to or dissimilar to the Hawaiian Ridge? Overheads-10
3) Find a sea or gulf that is similar to the Gulf of California. Explain how these two locations are similar. 4) If you were to travel north from Iceland along the Mid- Atlantic Ridge where do you think it would take you? 5) Where is the world s longest chain of trenches that have volcanic islands or seamounts? Overheads-11