Activity 3: Identifying Plate Boundaries Using Figures 1 and 2 (see attached fil

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Activity 3: Identifying Plate Boundaries Using Figures 1 and 2 (see attached files in dropbox) as a guide, sketch with colored pencils on Figure 10 below: a. b. c. Convergent boundaries in red The Divergent boundaries in blue The transform boundaries in green Use arrows to indicate the relative plate motions across the boundaries Figure 10. Shaded redef map of the world e and volcano evidence tectonics We have already learned earthquakes usually occur on or near plate boundaries. Most of these earthquakes occur within the crust at depths of less than 50 km beneath the surface. Some earthquakes are found at depths of up to 700 km within the mantle. These deep focus earthquakes occur in planar zones of seismicity called Wadati-Benioff zones after the two seismologists who discovered them. These zones were first discovered in the 1930s, long before the discovery of plate tectonics but we now associate them with the subducted lithosphere. The zones extend from the trench downward increasing in depth in the direction of subduction. Figure 11 is a West to East trending profile across the western margin of South America at 23 S latitude. The upper plot shows the bathymetry and topography showing the Peru-Chile Trench and the Andes Mountains and the horizontal position of Holocene volcanoes projected into the profile. The lower plot shows the locations of earthquakes projected into the section. In this activity, you will plot the position of the subducted Nazca Plate beneath the South American Plate in Chile and Argentina. You will also compare the position of active volkanoes (red triangles) relative to the position of the trench and the earthquakes (blue crosses) in the zone. 1) What is the minimum elevation (the trench) and the maximum elevation (the high Andes) on the

Explanation / Answer

Activity 2: Examining Plate Boundaries

Use the figure 9A-9B to the right to answer the following questions:

1. The large arrow in figure 9a show divergent plate boundary. Because two plate moves away from each other.

a. The crust is extending. As the plate move away from each other, the crust rupture due to extension and form ridge through which hot magmatic plume comes out to the surface.

b. Oceanic spreading ridge is associated with this plate boundary. Due to extensional effect, the crust become thinner and break down into two parts. After that they moves away from each other and form submarine mountain ranges called oceanic spreading ridges

c. Lithosphere is being created at this boundary. Along Mid Oceanic Ridge hot magma comes out to the surface and form new crust after cooling.

2) Small arrow shows conservative plate boundary. Because two plate slides each other and form transform fault boundary.

a. The crust is shearing. Due to transform fault boundary two plates slide each other that may cause shearing.

b. Transform fault is associated with that type of plate boundary. Huge stresses are set up that can cause portions of the rock to break.

c. The lithosphere is nither created nor destroyed at this boundary.

3) The plate boundary is convergent plate boundary. Because one plate converge under another plate.

a. The crust is compressing. Two tectonic plates collide in the convergent plate boundary where one plates will move beneath the other, known as subduction may form mountain ranges due to compressional effects and earthquakes are common.

b. Volcanic arc feature is associated with this plate boundary. Down going plate is being melted due to presence of higher pressure and temperature with other factors and form magma which comes out to the surface. Those are formed volcanic arc.

c. The lithosphere is being destroyed. Because one of the converging plates will move beneath the other, known as subduction. Due to heat and pressure down going crust and sediments being melted to form magma.

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