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Home , Antarctic Plate, Explorer Ridge, Juan de Fuca Plate, Juan de Fuca Ridge, Magnetic anomaly, North American Plate

Expedition The Biggest Plates on

FOCUS ADDITIONAL INFORMATION FOR TEACHERS OF DEAF STUDENTS Plate In addition to the words listed as Key Words, the fol- lowing word should be part of the vocabulary list. GRADE LEVEL 5-6 The words listed as Key Words are integral to the FOCUS QUESTION unit but will be very difficult to introduced prior to How do tectonic plates move, what are some con- the activity. They are really the material of the les- sequences of this , and how do magnetic son. There are no formal signs in American Sign anomalies document the motion at spreading cen- Language for any of these words and many are ters? difficult to lipread. Having the vocabulary list on the board as a reference during the lesson will be LEARNING OBJECTIVES extremely helpful. Students will be able to describe the motion of tec- tonic plates, and differentiate between three typical The second paragraph of the Background Information boundary types that occur between tectonic plates. has important information for use during the initial step of the Learning Procedure when you are explain- Students will be able to infer what type of bound- ing concepts of and drift. You should ary exists between two tectonic plates, given infor- demonstrate currents by setting up a heat- mation on and in the vicin- ed container of water and adding food coloring to it. ity of the boundary. Also it would be helpful to gather several flat rocks and demonstrate the motion of tectonic plates. It is Students will understand how magnetic anoma- important to demonstrate how small the movement is lies provide a record of geologic history around annually (several centimeters). spreading centers. MATERIALS Students will be able to infer the direction of motion  Copies of “Pacific Basin Tectonic Plates,” one between two tectonic plates given information on copy per student or student group magnetic anomalies surrounding the spreading  Copies of “Magnetic Anomalies on the Juan ridge between the plates. de Fuca Plate,” one copy per student or student group Students will be able to describe plate boundaries and tectonic activity in the vicinity of the .

1 Submarine Ring of Fire Expedition – Grades 5-6 Submarine Ring of Fire Expedition – Grades 5-6 Focus: Plate tectonics oceanexplorer.noaa.gov oceanexplorer.noaa.gov Focus: Plate tectonics

AUDIO/VISUAL MATERIALS charted the location of deep earthquakes in the  (Optional) Overhead transparency of cross- sec- Pacific . He found that sites are tion illustrating the main types of plate boundar- distributed in an arc that spanned both sides of the ies (download from U.S. web ocean. Five years earlier, Japanese seismologist Kiyoo Wadati had noticed a similar pattern, and site: http://pubs.usgs.gov/publications/text/Vigil.html) suspected that it was connected in some way to the  (Optional) Overhead transparency of map illus- idea of . He was right. trating the Ring of Fire (from U.S. Geological Survey web site: http://pubs.usgs.gov/publications/text/ Today we know that the outer shell of the Earth fire.html) (called the ) consists of about a dozen  (Optional) Overhead projector large plates of (called tectonic plates) that move several centimeters per year relative to each TEACHING other. These plates consist of a crust about 5 km Two or three 45-minute class periods thick, and the upper 60 - 75 km of the Earth’s . The plates that make up the lithosphere SEATING ARRANGEMENT move on a hot flowing mantle layer called the Classroom or groups of two to four students , which is several hundred kilometers thick. Heat within the asthenosphere creates con- MAXIMUM NUMBER OF STUDENTS vection currents (similar to the currents that can be 30 seen if food coloring is added to a heated contain- er of water). These convection currents cause the KEY WORDS tectonic plates to move. Plates may slide horizon- tally past each other at transform plate boundaries. Ring of Fire The motion of the plates rubbing against each other Asthenosphere sets up huge stresses that can cause portions of Lithosphere the rock to break, resulting in earthquakes. Places where these breaks occur are called faults. A well- known example of a transform plate boundary is Transform boundary the in . Another type of plate boundary is formed where tectonic plates are moving apart. At these diver- gent plate boundaries, magma (molten rock) rises Tectonic plate from deep within the Earth and erupts to form Spreading center new crust on the lithosphere. Most divergent plates boundaries are underwater ( is an excep- BACKGROUND tion), and form submarine ranges called The Ring of Fire is an arc of active volcanoes and oceanic spreading ridges. While the process is earthquake sites that partially encircles the Pacific volcanic, volcanoes and earthquakes along oce- Ocean Basin. The location of the Ring of Fire coin- anic spreading ridges are not as violent as they cides with the location of oceanic trenches and are at convergent plate boundaries where tectonic volcanic arcs, and was one of the early clues plates are being pushed together. Usually one of that led to the of continental drift and plate the converging plates moves beneath the other (a tectonics. In 1940, Hugo Benioff, an American process called subduction). Deep trenches are often seismologist (a scientist who studies earthquakes), formed where tectonic plates are being subducted,

2 3 Submarine Ring of Fire Expedition – Grades 5-6 Submarine Ring of Fire Expedition – Grades 5-6 Focus: Plate tectonics oceanexplorer.noaa.gov oceanexplorer.noaa.gov Focus: Plate tectonics

and earthquakes are common. As the sinking plate ics. When magma erupts along oceanic spreading moves deeper into the mantle, fluids are released ridges, it contains high concentrations of various from the rock causing the overlying mantle to par- , including magnetic minerals, such as iron tially melt. The new magma rises and may erupt to and that align with the Earth’s magnetic form volcanoes, often forming arcs of along like a compass needle. When magma cools the convergent boundary. to form solid rock (basalt), of magnetite become immobilized, and provide a record of On the tectonic plate, the production the position of the Earth’s when the and recycling of lithospheric crust has been likened magma erupted. to a huge conveyor belt system in which new crust is formed at the oceanic spreading ridges off the The Earth’s magnetic field periodically reverses (so western of North and , and that compass needles point to the south instead older curst is returned to the at the of the north) at irregular intervals that average convergent plate boundaries along the underwater around 400,000 years. The alignment of magnetic volcanoes and island arcs of the western Pacific. particles in crust that was formed during periods The 2002 Submarine Ring of Fire Expedition is of reversal is opposite to that of particles produced investigating the formation of new ocean crust at when the Earth’s magnetic field is oriented simi- the edge of the Juan de Fuca tectonic plate off the larly to the present. Scientists have found that the of western . This is a com- intensity of the Earth’s magnetic field varies around paratively small tectonic plate, and as a result has spreading centers; in some locations it is stronger a divergent boundary (with the ) as than normal, in other locations it is weaker. These well as a convergent boundary (with the North variations are called magnetic anomalies, and are American plate) relatively close together. The erup- the result of magnetic minerals in the basalt rocks. tion of Mt. St. Helen in 1980 was a result of the If the minerals were “locked” into the rocks when subduction of the Juan de Fuca plate beneath the the Earth’s magnetic field was similar to its present . The divergent boundary is magnetic field, then the magnetism of the minerals an active spreading center that is organized along is added to the Earth’s magnetic field, so the total three ridges: , , magnetic intensity is greater than normal; this is and . While Gorda and Juan de called a “positive magnetic anomaly.” On the other Fuca Ridges have been intensively studied, Explorer hand, if the minerals were “locked” into the rocks Ridge is virtually unexplored and is the focus of the when the Earth’s magnetic field was opposite to its 2002 Submarine Ring of Fire Expedition. present magnetic field, then the magnetism of the minerals opposes the Earth’s magnetic field, so the One of the first tasks for the expedition is to pre- total magnetic intensity is less than normal; this is pare maps of the seafloor around Explorer Ridge called a “negative magnetic anomaly.” to aid in identifying the most promising sites for investigation. In addition to topographic maps When positive and negative magnetic anoma- prepared with a multibeam sonar system (see http: lies are measured on either side of an oceanic //oceanexplorer.noaa.gov/explorations/02alaska/background/edu/ spreading center, they form a stripe-like media/mapping7_8.pdf, scientists will also make detailed pattern with the stripes running parallel with the measurements of magnetic fields around the Ridge ridge of the spreading center. Scientists have to reveal features that will not be detected by the reconstructed the history of magnetic reversals for sonar system. Measurements of magnetic variations the past 4 million years using a dating technique on the ocean floor have provided critical evidence based on isotopes of potassium and argon (see http: for theories of continental drift and plate tecton- //oceanexplorer.noaa.gov/explorations/02alaska/background/

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edu/media/mapping7_8.pdf. Using this information, they draw the students’ attention to the area around have been able to calculate the age of the magnet- the Juan de Fuca plate. Do not give too much ic anomaly “zebra stripes,” and the rate at which detail on the plate at this point; just talk about tectonic plates are moving away from their spread- where it is in relation to the United States and ing centers. . Be sure the students realize that the small size of the plate brings convergent and This lesson is divided into two parts. In the first divergent boundaries relatively close together. part, students will infer whether plate boundaries The fact that subduction of the plate at its con- associated with the Pacific Ring of Fire are diver- vergent boundary with the North American plate gent, convergent, or transform based on informa- caused the Mount St. Helen’s eruption should tion about earthquakes and volcanic activity in provide an opportunity to spark students’ interest. the vicinity of the boundaries. In the second part, students will use magnetic anomaly data to draw 4. Distribute copies of “Magnetic Anomalies on the inferences about the spreading center system on the Juan de Fuca Plate” to each student or student divergent boundary of the Juan de Fuca plate. group. Have each group discuss the handout, and write their conclusions on the worksheet. LEARNING PROCEDURE Lead a discussion of the reasoning behind these 1. Explain the concept of plate tectonics and conti- conclusions. Students should infer that the mag- nental drift. Be sure students understand the idea netic anomalies occur on either side of a diver- of convergent, divergent, and transform bound- gent plate boundary (between the Juan de Fuca aries, as well as the overall type of earthquake and Pacific plates), and that the youngest rocks and volcanic activity associated with each type are closest to the spreading center at the bound- of boundary (strong earthquakes and explosive ary of the two plates. Students should also real- volcanoes at convergent boundaries; slow-flow- ize that the interruptions in the anomaly “stripes” ing volcanoes, weaker earthquakes at divergent represent separate spreading centers resulting boundaries; strong earthquakes, rare volcanoes from faults along the boundary between the at transform boundaries). Discuss trans- plates. At this point, name the three ridges where fers involved in plate , earthquakes, and these spreading centers are located (Gorda volcanoes. You may want to use materials from Ridge to the south, Juan de Fuca Ridge in the “This Dynamic Earth” and/or “This Dynamic middle, and Explorer Ridge to the north), and Planet” (see Resources section), but do not give introduce Explorer Ridge as the site of the 2002 away the answers to the predictive exercise on Ocean Exploration Ring of Fire Expedition. the Pacific Basin Tectonic Plates. THE BRIDGE CONNECTION 2. Distribute copies of “Pacific Basin Tectonic Plates” www.vims.edu/bridge/geology.html to each student or student group. Have each group decide what type of boundary exists at the THE “ME” CONNECTION indicated sites. Tabulate each group’s results, and Have students write a first-hand account of a visit lead a discussion of the reasoning behind their to a plate boundary, describing where the bound- conclusions. If you want to use this exercise for ary occurs and what conditions are found there. evaluation, collect the worksheets before discus- sion. CONNECTIONS TO OTHER SUBJECTS English/Language Arts, Geography 3. Explain the idea of magnetic anomalies, and

4 5 Submarine Ring of Fire Expedition – Grades 5-6 Submarine Ring of Fire Expedition – Grades 5-6 Focus: Plate tectonics oceanexplorer.noaa.gov oceanexplorer.noaa.gov Focus: Plate tectonics

EVALUATION FOR MORE INFORMATION Both worksheets may be used to evaluate stu- Paula Keener-Chavis, National Education dents’ understanding of the concepts presented. Coordinator/Marine Biologist Alternatively or additionally, students may be asked NOAA Office of Exploration to define key words, and/or identify the type of Hollings Marine Laboratory boundaries and expected conditions at the junc- 331 Fort Johnson Road, Charleston SC 29412 tions of other tectonic plates. 843.762.8818 843.762.8737 (fax) EXTENSIONS [email protected] Have students visit http://oceanexplorer.noaa.gov to keep up to date with the latest Ring of Fire Expedition ACKNOWLEDGEMENTS discoveries. This lesson plan was developed by Mel Goodwin, PhD, The Harmony Project, Charleston, SC for the RESOURCES National Oceanic and Atmospheric Administration. http://oceanexplorer.noaa.gov – Follow the Ring of Fire If reproducing this lesson, please cite NOAA as the Expedition daily as documentaries and dis- source, and provide the following URL: coveries are posted each day for your class- http://oceanexplorer.noaa.gov room use. A wealth of information can also be found at this site.

http://pubs.usgs.gov/publications/text/dynamic.html#anchor19309449 – On-line version of “This Dynamic Earth,” a thorough publication of the U.S. Geological Survey on plate tectonics written for a non- technical audience

http://pubs.usgs.gov/pdf/planet.html – “This Dynamic Planet,” map and explanatory text showing Earth’s physiographic features, plate movements, and locations of volcanoes, earthquakes, and impact craters

NATIONAL SCIENCE EDUCATION STANDARDS Content Standard A: Science as Inquiry • Abilities necessary to do scientific inquiry • Understanding about scientific inquiry

Content Standard B: Physical Science • Transfer of energy

Content Standard D: Earth and Science • Structure of the Earth system

4 5 Submarine Ring of Fire Expedition – Grades 5-6 Submarine Ring of Fire Expedition – Grades 5-6 oceanexplorer.noaa.govTectonic Plates Bordering the Pacific Basin Focus: Plate tectonics oceanexplorer.noaa.gov Focus: Plate tectonics

Student Handout Student Handout Tectonic Plates Bordering the Pacific Basin

North American Plate

Juan de Fuca Plate Philippine Plate Pacific Plate

Cocos Plate

Australian Plate

Antarctic Plate Submarine Ring of Fire Expedition – Grades 5-6 Submarine Ring of Fire Expedition – Grades 5-6 oceanexplorer.noaa.gov Focus: Plate tectonics oceanexplorer.noaa.gov Focus: Plate tectonics

Student Handout Student Handout Magnetic Anomolies on the Juan de Fuca Plate

British Columbia

Vancouver Island

Juan de Fuca Strait

Age of (millions of years) B 11

9

7

5

3

0

A

Source: http://pubs.usgs.gov/publications/text/dynamic.html#anchor19309449