5 now mentally close up the atlantic ocean by

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floor? _____________________________________________________________________________________ __________________________________________________________________________________________ 5. Now mentally close up the Atlantic ocean by “reversing” the plate movement along the transform faults (at the Mid-Atlantic Ridge). This is what the world looked like about 180 million years ago. What country or con - tinent was adjacent to Boston before the Atlantic opened? ________________________________________ III. Transform Boundaries (Draw a map view below; use the same symbols as before) 6. Describe earthquake locations and depths at transform boundaries. What do you think causes earthquakes at these plate boundaries? Why is the pattern different than at convergent boundaries? __________________________________________________________________________________________ __________________________________________________________________________________________ __________________________________________________________________________________________
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Lab 1: Plate Tectonics 19 Activity 2: Google Earth questions For this activity, you will need to use Google Earth software, which is on all ATUS computer labs at WWU. If you’d like to load this software on your own computer, it is free to download at index.html . Use Google Earth to open some files to aid our investigation of plate tectonics. Open the Canvas page for this lab and go to Modules 1 Lab 1 1 Lab 1 - Plate Tectonics.kmz . Now look at Google Earth and you’ll see the plate names and boundaries colored by boundary type. 1. Fly to the Atlantic ocean (use the search box). a. What kind of plate boundary runs the length of the Atlantic ocean? ________________________________ b. Next, fly to Iceland (use the search box again). Considering your answer to the previous question, what do you think has been happening in Iceland, and will continue to happen? ______________________________ ________________________________________________________________________________________ What effect might this have on the size of Iceland? _______________________________________________ 2. Zoom out and look at the entire globe. Notice that some plates have continents and some do not. Can a single plate have both oceanic and continental parts? ____________________________________________________ a. Name two plates that support your answer. ______________________ _________________________ 3. Turn on the Volcanoes layer (Layers window 1 Gallery 1 Volcanoes) in Google Earth. Now fly to western Washington State so that you can see the plate boundaries. Note that all three boundary types are present just offshore. The volcanoes in the Cascade Range are the result of subduction. In this particular subduction zone water is car - ried down with the subducting plate, causing the mantle to melt and create magma. Melting happens at a depth of around 100 km. The distance between the trench (the plate boundary) and the volcanic arc (e.g. Cascades) is called the arc-trench gap . The arc-trench gap helps us determine whether a subduction zone is steep or shallow. A wide arc-trench gap indicates a shallow subduction zone, whereas a narrow arc-trench gap indicates a steep subduction zone . The arc- trench gap is measured from the peak of a volcano directly across the horizon to the trench. a. Using the Google Earth ruler tool (see pg. 7), what is the arc-trench gap for Mt. Rainier? ______________km b. Now investigate Nicaragua. What is the arc-trench gap for Masaya volcano? _______________ km c. In the boxes below, sketch the cross sections for the two subduction zones for which you measures the arc- trench gap. On the vertical axis, use 0 km for the Earth’s surface. Plot the trench at 0 km, 0 km ( ). Remember, the trench is located where the two plates meet. Label the trench (T), the zone of melting (M), and the location of the volcano (V).
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