Ateneo de Manila University Department of Political Science
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- cours - matière potentielle : description
- cours magistral
- cours - matière potentielle : requirements
- cours - matière potentielle : objectives
- cours - matière potentielle : outline preliminaries i. concepts
- cours - matière potentielle : requirements students
- expression écrite
- philippine context
- social contract theorists
- policy process
- political culture
- elections
- attendance attendance
- attendance although attendance
- public policy
- problems
- politics
- students
PHY 1040 PHYSICAL GEOLOGY VIDEO COURSE ANSWERS TO LAB EXERCISE 4 Plate Tectonics and the Origin of Magma 1. See completed Figure 2.3. 2. After referring to Figure 2.3 which you partially completed in #1, as well as Figure 2.4, you should have reached the following conclusions: a. If Earth is expanding in size, then the crust would lengthen due to normal faulting. b. If Earth is shrinking, the crust would shorten due to reverse faulting (mostly). c. If Earth’s crust fractures and there is no expansion nor shrinkage in overall size, the crust must be affected by shear stress and the resulting strikeslip faulting. 3a. Along divergent boundaries, there is mostly tensional stress caused by plates moving apart (diverging). Volcanic activity occurs there as seafloor basalts are formed. This is accompanied by normal faulting of the relatively thin lithosphere. b. Along convergent boundaries, the stress is mostly compressive, due to the plates moving together (converging). In addition to the reverse faulting, both shallow, intermediate and deep, the subducting plate melts and volcanic island arcs form (on an oceanic plate) or chains of volcanic mountains, like the Andes (on a continental plate). c. Along transform boundaries, shear stress is generated as the plates slide past one another. Transform boundaries are actually zones of large transform (strikeslip) faults. 4. Refer once more to the completed Figure 2.2. 5. Assuming you can recognize the three types of plate boundaries: red for divergent boundaries, dashed for transform boundaries (these are not easy to see, so look carefully) and hachured (black with little triangles) for convergent boundaries, you should have seen 1 that about each type occupies about /3of the total boundary length. 6. Based on what we have seen in the earlier parts of this exercise, it seems that the size of Earth is not changing. There is evidence of equal amounts of crustal compression, tension and shear. It would appear, then, that lithosphere is created at divergent plate boundaries, is recycled back into the mantle at convergent boundaries, and is neither created nor recycled at transform boundaries.
