ODJ_Tectonics
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Apr 3, 2024
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Ocean Discovery Journal Plate Tectonic Boundaries & Seafloor Spreading Follow the instructions below and use these sheets to record your answers to the Ocean Discovery Plate Tectonic & Seafloor Spreading exercise. Scientists commonly use multiple tools, databases, and sources of information. This activity similarly uses two different web map-tools. The Jules Verne Jr
mapping tool was developed and maintained by UNAVCO in Boulder, Colorado. We will additionally be using This Dynamic Planet
interactive map, a collaborative project between the Smithsonian Institution, the United States Geological Survey (USGS), and the Office of Naval Research Laboratory. The Jules Verne Jr mapping tool is located on the web at: http://jules.unavco.org/VoyagerJr/Earth
This Dynamic Planet interactive map is located on the web at: http://baird.si.edu/minsci/tdpmap/viewer.htm
You need to complete ALL
sections of the exercise recording your answers on this worksheet as you go. These answer sheets should be added to your Ocean Discovery Journal
for review and later assessment. You may also use the Notes
section at the bottom to record other thoughts or questions you may have that arise during your completion of this exercise. Discovering Plate Boundaries Lithospheric Plates & Plate Boundaries Step 1> Instructions Open the Jules Verne Voyager Jr application in your web browser. Take a moment to familiarize with the simple functions of the map-tool. Under Add Feature(s)
click on “Tectonic Plates.” The map-tool will draw in the word’s plate boundaries, using colors to differentiate between divergent, convergent and transform margins. Click on the Legend On/Of button. The legend should “pop up” in a separate window. Study the map noting the general location of major plate boundaries. Step 1> Questions 1. Place in order from greatest length on the Earth’s surface to least, the tree types of plate boundaries. Discovery Activity Plate Tectonics
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When Wegener devised the Continental Drift hypothesis he envisioned the continents moving either over or through the ocean basins. This was one of his greatest difficulties. Geophysicists correctly pointed out that the frictional resistance in such a scenario would be impossibly large and the rocks would simply shatter. Examine the relationship between continents and plates by looking at the map you created. 2. In general, do continental shorelines coincide with plate boundaries? 3. Do lithospheric plates tend to have both continents and oceans imbedded within them? Now look at the coastlines of North America. Continental margins that are associated with a plate boundary are referred to as “active margins.” Those coastlines that are not associated with a plate boundary are referred to as a “passive margin.” 4. Of the Pacific, the Gulf, and the Atlantic Coasts, which are passive and which are active margins? If any are active, list the types of plate boundaries that are present. Earthquake Depth Step 2> Instructions Under Add Feature(s)
click on “Earthquakes.” Then click on the Update Map button. The map-tool will draw in the global seismicity. Each earthquake is represented by an epicenter. The color of the epicenter plot is related to the depth of focus (the center point of the area of rupture on a fault that generated the earthquake). Click on the Legend On/Of button if you can’t see the legend. The legend should “pop up” in a separate window, now with a key relating color of the plot to depth of foci. Step 2> Questions 5. In general how do zones of seismicity compare to plate boundaries?
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Look at areas of the Northwestern Pacific Basin. This area is part of the Ring of Fire
of the circum Pacific region. It is dominated by subduction zones. You can click on the map to zoom in on the area. Examine the pattern of seismicity across the subduction zones. 6. Describe the seismicity above subduction zones. How does it compare to the seismicity seen along divergent and transform margins? 7. Look carefully across the Japanese Island arc. Here the Pacific Plate is diving under Japan. Do you notice any trend in seismicity across the island arc? Explain. Volcanism Step 3> Instructions Now click on World Map to see the entire map view. Select Add feature(s) “Volcanoes” to see the distribution of active volcanoes on the Earth. Study the patterns of volcanism that appears on the map. Step 3> Questions 8. How does the distribution of volcanoes compare to plate boundaries? 9. Describe the pattern of volcanism in the area of the circum Pacific region commonly referred to as the Ring of Fire. Earthquake Magnitude Step 4> Instructions The map and the data presented in Jules Verne Voyager Jr
doesn’t give us a full picture of earthquake and volcanic processes at plate boundaries. To explore a bit further we will need to use another mapping tool. Open the This Dynamic Earth interactive map and become familiar with the tools and layer control. Start by checking all of the magnitude selections for earthquake data to plot epicenters for these on the map. Make sure to uncheck the volcanoes layer as this will obscure
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earthquake data. Your map will look similar to the one you generated in Jules Verne Voyager Jr. Now uncheck the layers for earthquakes less than magnitude 8.0. You will have very few epicenters left on the map. Before proceeding make sure the map also has all of the tectonic boundary layers checked for the map. Step 4> Questions 10. Were the major earthquakes associated with primarily one type of boundary? If so which type? Sea-floor Spreading Mid-Atlantic Ridge Step 5> Instructions: Go back to Jules Verne Voyager Jr. For Features check “Tectonic plates,” to draw in the various plate boundaries. Click on Legend
and note the color code used for each type plate boundary. Examine the divergent plate boundary in the middle of the Atlantic Ocean and answer the following Question. Step 5> Questions: 11. How does the shape of the plate boundary compare with the shape of the coastlines of South America and Africa; with North America and Europe? 12. Does this relationship support what you understand about the breakup of Pangaea? Explain. Ocean Floor Age Step 6> Instructions: In Jules Verne Voyager Jr. under Select a base map
click on Ocean floor ages. Your map will now show only the seafloor with ages marked by different colors. Click on the Legend on/off button so that you can see the relationship of color to actual age of the rocks of the seafloor. In general the darker “cooler” colors are older and the brighter “hot” colors represent younger seafloor. Examine the relationship especially within the Atlantic Ocean Basin.
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Step 6> Questions: 13. Where are the youngest rocks in the Atlantic Ocean? 14. Where are the oldest Atlantic rocks? 15. Does this support the Vine-Matthew-Morley hypothesis of seafloor spreading? Explain. 16. Look at the pattern of ocean floor ages for the North Atlantic and South Atlantic Ocean Basins. During the break up of Pangaea did the North Atlantic or South Atlantic Ocean Basin open first? How can you tell? Acknowledgements The JV Voyager Jr
. is an interactive map tool developed by UNAVCO with support from NASA and the National Science Foundation for the study of global-scale geodynamic processes. The imagery is taken from the Jules Verne Voyager, a map-making tool that uses the Generic Mapping Tool kit (GMT). GMT is developed and maintained by Paul Wessel (University of Hawaii) and Walter H. F. Smith (National Oceanographic and Atmospheric Administration (NOAA) with help from a global set of volunteers, and is supported by the National Science Foundation. This Dynamic Planet
interactive map is a collaboration between the Smithsonian Institution, the US Geological Survey, and the Office of Naval Research Laboratory. About the Earth Discovery Project The Earth Discovery Project is a collaborative effort to integrate hands-on discovery-based learning with modern research tools in undergraduate geoscience education. The approach is to develop and disseminate a comprehensive set of learning resources and experiences supporting systemic educational reform. The logo of the Earth Discovery Project portrays the earth as a three-dimensional puzzle. The globe used in the logo is from NASA’s Blue Marble Project
. The Blue Marble
is a unique view of the earth, which integrates numerous data sets to construct a “true-color” three-dimensional globe.