Introduction to the Seafloor Original Source: Dr. Leslie Sautter
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- Earth and Space Science – Content Standard D Focus Questions
- Time Frame
- Procedure Students should follow the steps below, found on the STUDENT PAGES, while taking notes in their science notebook. Information for the teacher is provided in
- Summarize your observations and discoveries by answering the questions on the next page. Questions
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Introduction to the Seafloor Original Source: Dr. Leslie Sautter (Dept. of Geology, College of Charleston) Grade Level: 5th & 8th Grade SC Standards: 5th – IIIA1a,b,d,f,g; IIIA2a,b,c 8th – IIIB1c,f,g; IIIB3b,c,j,k; IIIB4a,b,f National Standards: Earth and Space Science – Content Standard D Focus Questions What are the major types of seafloor features? Do these seafloor features show any patterns and/or associations with each other? Objectives Students will: observe various features of the seafloor depicted on a physiographic map of the ocean floor. identify ridges, trenches, seamounts, volcanic island chains and fracture zones and describe their large-scale characteristics. examine the geographic associations between features (i.e., those that are parallel to one another and those that are perpendicular to one another). Key Words ocean basins arcuate and linear features mid-ocean ridges fracture zones trenches seamounts, seamount chains volcanic islands, volcanic mountains Materials For each group of students: photocopy of STUDENT PAGES. physiographic map of the ocean floor. This activity was developed using the TASA Graphic Arts map. ($5 from Syzygy Arts, Inc., http://www.syzygy06.com) large sheet of tracing paper (if not available, use plain paper) pencil and eraser 4 color pencils For the teacher: physiographic map of the ocean floor, large version of the same map, if possible globe - inflatable works well (Note: the globe needs to have a light colored ocean so that the pen marks will show) transparency marker pens, four different colors (to write on the globe) baseball or softball (optional) Time Frame One to two 50-minute class periods Suggested Learning Environment Students should work in cooperative groups of 3-4. With enough materials, this activity works well for an entire classroom of students. Relevant pages in “Of Sand and Sea Chapter I, The Ocean Planet, pp. 1-6. Teacher Preparation Stress to students that this is an observational activity, and that they are doing what oceanographers did in the 1950s and 1960s as they first began to have a "picture" of the ocean floor. This activity is not intended to teach students how these seafloor features were formed. It is designed to be the first in a series of three activities. “Introduction to the Seafloor” should be followed by “Quakes and Plates” and “The Puzzling Plates.” The teacher may lead the activity, by reading the instructions on the STUDENT PAGES aloud, and posing questions to the class as a guided inquiry. Or, the teacher may wish the activity to be student-led, providing STUDENT PAGES to each student group. It is very important to remind students that this activity is not designed to teach the formation of these seafloor features. It is to observe the features and identify associations among the different types of features. Encourage all students to participate, and when they locate features ask them point to the map and trace the features. This ensures that all students in the group are finding the designated features together. To protect maps from being marked on, ask students not to use pens or pencils to point out features on the map. Throughout this activity the student is asked, “What is the geographic association between ___ and ___?” Discuss with students that this type of question is seeking an answer to identify patterns in the seafloor features and if the patterns occur several times. Try to get the students to use geometric terms such as ‘parallel to’ or ‘perpendicular to.’ A sentence describing the association might be structured, “___ and ___ are parallel to each other,” or “___ is perpendicular to ____.” Students will conduct the activity by following the steps listed in the STUDENT PAGES. The procedure follows, and notes for the teacher are bulleted (diamond-shaped bullet), in blue italics. Assessment questions are included for students to answer in a science notebook or on separate pages to hand in. Guidelines for evaluating student answers are included. Procedure Students should follow the steps below, found on the STUDENT PAGES, while taking notes in their science notebook. Information for the teacher is provided in blue italics. Name and locate all of the continents. North America, South America, Africa, Eurasia, Australia, Antarctica Note that Europe and Asia are not separate continents! Geologically, they are on the same continental land mass, whereas politically they are separate. Identify linear (straight-line) and arcuate (curved-line) features on the continents. Do not include rivers or coastlines. Identify the major mountain chains and trace them with your finger. Be certain to include the following: Andes Mountains (S. America), Appalachian Mountains and Rocky Mountains (N. America), Himalayas (northern India), Ural Mountains (Russia), and the Caledonian Mountains (on the coast of Scandinavia). Find linear lakes in Africa. These lakes comprise the East African Rift Valley. Move to the ocean. Name and locate the four major ocean basins (major oceans). Pacific, Atlantic, Indian and Arctic Oceans. Most maps do not show all of the Arctic Ocean. You may have heard of the Southern Ocean, but that is not an ocean basin. Oceanographers study the “Southern Ocean” because of the currents and circulation that connects the southern portions of the Pacific, Atlantic and Indian Oceans. 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. Remember that the Earth has only one interconnected ocean; however there are 4 major ocean basins. Locate the following seas and gulfs: Atlantic Ocean: Mediterranean Sea, Caribbean, Norwegian Sea, Gulf of Mexico Indian Ocean: Red Sea, and Arabian Sea Pacific Ocean: Gulf of California Note the linear nature of the Red Sea and the Gulf of California. 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. Locate examples of ridges, trenches, volcanic island chains, seamount chains, fracture zones, etc. 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. Find several other mid-ocean ridges. Pacific Ocean: East Pacific Rise and Juan de Fuca Ridge Indian Ocean: Southwest Ridge, Southeast Indian Ridges and Carlsberg Ridge What other type of seafloor feature is also found along mid-ocean ridges? Fracture zones are associated with mid-ocean ridges. The ridge segments are offset from one another, along these fracture zones. Find the Hawaiian Ridge. How does it differ from mid-ocean ridges? The Hawaiian Ridge is not broken into numerous ridge segments which are offset by fracture zones. It is a very linear ridge and is quite different from the others previously examined. It is made of the chain of seamounts and volcanic islands (to be observed in the next section). Find the Ninety East Ridge in the Indian Ocean. Is it more like a mid-ocean ridge or the Hawaiian Ridge? The Ninety East Ridge is not broken into numerous ridge segments and is more like the Hawaiian Ridge. 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. Compare this system of connected ridges to the seam of a baseball. (See if your teacher has a baseball to view.) Examine the Pacific Ocean and locate several fracture zones. Find the following fracture zones: Pacific Ocean: Eltanin, Challenger Atlantic Ocean: Gibbes, Romanche, Rio Grande Indian Ocean: Owen, Prince Edward What is the geographic association between ridges and fracture zones? Fracture zones are typically perpendicular to ridge segments. Ridge segments are offset from one another, with fracture zones between them. (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. If you cannot write on the only globe available, then use masking tape to mark the mid-ocean ridges. Discuss the fracture zone locations. Find several ocean floor trenches. As you locate each, trace them with your finger. Locate the following trenches: Pacific Ocean: Aleutian Trench, Kuril Trench, Japan Trench, Mariana Trench, Philippine Trench, Tonga Trench, Peru-Chile Trench, and the Middle America Trench. Atlantic Ocean: Puerto Rico Trench, Cayman Trench, South Sandwich Trench Indian Ocean: Java Trench 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! 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. (Optional) Using a third color of transparency marker pen, draw the location of trenches on the globe. Again, you may want to use masking tape if you are unable to write on the available globe. Use a permanent marker to color the masking tape once it’s on the globe, to distinguish trenches from mid-ocean ridges. 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. Locate the following volcanic island chains and trace them on your map with your finger: Pacific Ocean: Aleutian Islands, the Kuril Islands (southwest of the Kamchatka Peninsula), Japan, and the Philippine Islands. Note that Japan is comprised of a few volcanic islands (seamounts that have grown above sea level). These volcanoes have merged to form one large island. What is the geographic association between trenches and seamount (or volcanic island) chains? All of the seamount chains listed have a strong parallel association with trenches. There are, however, other seamount chains that have no trench nearby. Nearly all trenches have seamount chains parallel to them. Locate the following volcanic mountain chains (on the continents): Andes Mountains, Sierra Madre (Central American), and the Cascade Mountains (in Oregon and Washington). What is the association between volcanic mountain chains and trenches? All these volcanic mountain chains are associated with a nearby trench that is parallel to them. (Optional) Using a fourth color of transparency marker pen, draw the location of seamount chains on the globe. Again, you may want to use masking tape if you are unable to write on the available globe. 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? Is this the same kind of ridge as a mid-ocean ridge? No, it is different. It does not have fracture zones. What occurs to the volcanic chain at approximately 170°E longitude? What is this feature called? The seamount chain bends northward. This is called the Emperor Seamount Chain. Are there any trenches associated with either of these two seamount chains? Is the association similar to other seamount chains and trenches? There are no trenches parallel to either of these seamount chains; however, students may observe that the Aleutian Trench is perpendicular to the Emperor Seamount Chain. If this observation is made, ask if they can find any other seamounts that are perpendicular to trenches. They are unlikely to find them. 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? This seamount chain has no trench associated with it, but is along the same arcuate line as the Eltanin Fracture zone. Summarize your observations about seamount chains, volcanic island chains, volcanic mountain chains, trenches and fracture zones. Provide an example for each observation. These seamounts are confusing, so they need to make statements such as the following: 1) Most (if not all) trenches have an associated seamount/volcanic island chain or continental volcanic mountain chain parallel to them. Examples: Aleutian Trench and the Aleutian Islands; Peru-Chile Trench and the Andes Mountains 2) Some seamount/volcanic island chains have no trenches associated with them. Example: Hawaiian Island Ridge seamount chain. 3) Some seamount/volcanic island chains are associated with fracture zones – they are aligned with these fracture zones. Example: Louisville Ridge seamount chain and the Eltanin Fracture Zone. 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? The Aleutian Islands are north of the trench. 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. What are the trenches you encountered along the way? Were there any other seafloor features associated with those trenches? There are many trenches that interconnect along this path. Students may choose a path that includes either the Philippine Trench or the Mariana Trench. There are volcanic islands all along this path. As you head generally eastward from the Philippine region, you will find many broken segments of trenches, and a lot of volcanic islands. What is the name of the linear trench north of New Zealand? This is the Tonga Trench. 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? Students may find the Chilean Ridge, the Nazca Ridge or the Galapagos Ridge. Each of these ridges branches off of the EPR and runs eastward, ending at the South American coast (or at the Peru-Chile Trench). What feature can you now follow all along the coast of South America towards Central America? The Peru-Chile Trench is parallel to the coast of South America. What seafloor feature do you encounter parallel to the coast of Central America? The Middle America Trench is parallel to the Central American coast. 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. 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). 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). 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! 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: 
Now let’s examine the Atlantic Ocean. Would you be able to take a similar circum-Atlantic tour following seafloor features? No, there are very few trenches in the Atlantic Ocean and, unlike the Pacific Ocean they do not rim the basin. Can you find seamount chains similar to the Hawaii, Nazca and Louisville Ridges of the Pacific Ocean? Yes, but there are not nearly as many and they are fairly short. The Walvis Ridge (off of Africa) and the Azores Islands are both chains of seamounts and volcanic islands. There are also short volcanic island chains associated with the few trenches that exist in the Atlantic. Make a chart that compares the abundance of trenches, mid-ocean ridges, fracture zones, volcanic island chains, and volcanic mountain chains of the Pacific and Atlantic Ocean basins. Review the associations you’ve observed among ridges, trenches, volcanic island chains, seamount chains and continental volcanic mountain chains. Continue with your exploration by doing the activity “Quakes and Plates” followed by “The Puzzling Plates.” Summarize your observations and discoveries by answering the questions on the next page. Questions (Assessment) 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. 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 Mid-ocean ridges have linear segments that are offset by linear or arcuate fracture zones. They are found in the mid-Atlantic and in the southeastern portion of the Pacific. There are 3 branches of a mid-ocean ridge in the Indian Ocean. There is also a ridge that runs across the Arctic Ocean (though it is not evident on most seafloor maps). Atlantic Ocean Example: Mid-Atlantic Ridge and Romanche Fracture Zone or Gibbes Fracture Zone Pacific Ocean Example: East Pacific Rise and Eltanin Fracture Zone Indian Ocean Example: Mid-Indian Ridge and the Owen Fracture Zone Fracture zones are the linear or arcuate features that lie in between the offset ridge segments (examples are above). Some of these fracture zones are parallel to or aligned with seamount chains. Pacific Ocean Example: Eltanin Fracture Zone and the Louisville Ridge Trenches are the linear or arcuate features found mostly in the Pacific, and occur all along the northern and western edge of the Pacific Ocean Basin. There are fewer in the other 3 ocean basins. Trenches are almost always found parallel to a chain of volcanoes. These volcanoes may be seamounts or volcanic islands, or they may be continental volcanoes. Pacific Ocean Example with volcanic islands: Aleutian Trench and the Aleutian Islands; Kuril Trench and Kuril Islands; Philippine Trench and Philippine Islands Atlantic Ocean Example with volcanic islands: Puerto Rico Trench and Puerto Rico Pacific Ocean Example with continental volcanoes: Peru-Chile Trench and the Andes Mountains; Juan de Fuca Trench and the Cascade Mountains 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? The Hawaiian Ridge is a chain of seamounts and volcanic islands. It is not a series of linear ridge segments that are offset by fracture zones. The Ninety East Ridge in the Indian Ocean is similar to the Hawaiian Ridge, although it doesn’t have the distinct, individual seamounts. Find a sea or gulf that is similar to the Gulf of California. Explain how these two locations are similar. The Red Sea is narrow and linear, similar to the Gulf of California. Both of these seas have a small mid-ocean ridge in the middle of them. If you were to travel north from Iceland along the Mid-Atlantic Ridge where do you think it would take you? The Mid-Atlantic Ridge would lead me north up and over the north pole (or close to it!), into and across the Arctic Ocean. Where is the world’s longest chain of trenches that have volcanic islands or seamounts? The longest chain of trenches in the world is in the northern and western Pacific Ocean basin. It begins with the Aleutian Trench and ends with the Philippine Trench (or the Mariana Trench, depending on the path you take). Source: Dr. Leslie Sautter, Project Oceanica, Dept. of Geology and Environmental Geosciences, College of Charleston, SC. website: http://oceanica.cofc.edu email: oceanica@cofc.edu phone: 843-953-5586 Funding for the COASTeam Program was provided by the South Carolina Sea Grant Consortium. http://oceanica.cofc.edu/coasteam/ COASTeam Program, Project Oceanica, College of Charleston Directory: word word -> Illinois state board of education word -> Ccm module 4 Persons, Families, and Corporate Bodies Associated with a Work word -> Northern territory of australia word -> Number: caveat in the [Will/Will and Codicil/Estate of] word -> Word Wall Chants Use these as fun ways to practice word wall words at home! word -> Noaa corporate office nominations word -> List of accessible executive records word -> To visit our student-to-student file sharing network word -> What We Owe Jehovah’s Witnesses word -> PriceWaterhouseCoopers Archive 148 linear feet in 98 record cartons and 4 flat boxes. 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