Exam #4
Geology 101
Fall 2000

True-False

1. The amount of heat coming out of the Earth is the same everywhere. 2. P-waves, which are the fastest type of seismic wave, are also called shear waves. 3. Seismic waves follow straight paths through the Earth. 4. The Earth's core is entirely molten. 5. The Moho is a discontinuity at the base of the crust. 6. The crust is extremely thin or even nonexistent in the center of very old continents. 7. The 1964 Good Friday earthquake had a magnitude of 14. 8. Horsts and grabens are associated with block faults. 9. Shear forces produce strike-slip faults. 10. Earthquakes often occur in subduction zones. 11. Stress refers to forces that might cause a rock to deform; strain refers to the actual deformation itself. 12. Rocks that experience stress deform plastically for a while, but as stress increases eventually they deform elastically. 13. Mountain building is most often associated with a divergent plate boundary. 14. The east coast of the United States is a passive margin. 15. Excess gravity is one of the reasons that geologists concluded that mountains have deep crustal roots. 16. To geologists, the term orogenesis refers to mountain building. 17. The lithosphere is composed of a bunch of "floating" pieces of the Earth's crust. 18. The Japanese islands and the Andes Mountains are both the results of subduction related volcanism. 19. Today we find glacial deposits in places near the equator - this is evidence for continental drift. 20. Pangaea is the name given to a "supercontinent" which broke apart about 200 mya to form the present day continents. 21. The Hawaii islands formed due to subduction. 22. The Earth's lithosphere and the Earth's crust are almost the same thing, except that the lithosphere includes parts of the uppermost mantle. 23. The Earth's mantle and the Earth's asthenosphere are almost the same thing, except that the asthenosphere is missing the uppermost mantle. 24. Convection of heat is an insignificant process within the Earth. 25. In general, seismic waves travel faster deeper in the Earth compared to near the surface. 26. The WWSSN is a rock and roll group from Japan. 27. An earthquake measuring 7 on the Richter scale is about ten times more powerful than one measuring 6. 28. Surface waves, in general, are responsible for the most damage to buildings. 29. Some earthquakes originate at depth greater than 100km in the earth. 30. The San Andreas fault is an example of a dip-slip fault

.31. Look at the drawing and put the correct answers in the table below. Some words/terms you might want to use are mantle, outer core, inner core, oceanic crust, continental crust, asthenosphere, lithosphere, upper mantle. You could also make up your own answers but, hey, why bother? (Drwing of cross section of Earth included here.)

A
B
C
D
E
F
G
H

32. Both domes and basins may appear as bull's-eye patterns on geological maps. That is, rings of rock around each other with each ring being a different formation. So, if a geologist finds such a pattern, how can they tell if they are looking at a dome or a basin? Use a good drawing to answer this question if it would help.

33. One bright young geology student told me that they thought that the places in the world that had the most earthquakes correlated pretty well with the places in the world that have the most volcanoes. Is this true? What was the student thinking about - give some examples. Why does it make sense to expect earthquakes and volcanoes to often occur in the same places?

34. Your book tells you that the Earth comprises several different distinct concentric layers. How do geologists know that the Earth consists of concentric layers that have different

35. Geologists have learned about the Earth's magnetic reversals by studying the ocean floor. Explain how ocean floor studies have helped geologists chronicle magnetic reversals? Why do we have no information about reversals older than about 75 million years ago?

36. In some parts of the world, compressional forces squeeze the earth's crust together. In other places, the crust is pulled apart by extensional forces. What sorts of folds or faults form in areas of compression? What sorts of fold or faults form in areas of extension?