Use data graphed in Figures 8.18 and 8.20 to write a paragraph explaining why geologists interpret the lower continental crust to consist of igneous rocks that are more mafic than the rocks composing the upper continental crust
What will be an ideal response?
Figure 8.20 shows that P-wave velocity increases downward in the crust in a gradual way until about 35 km where there is an abrupt increase in velocity. The gradual increase could simply be a result of the deeper rocks experiencing higher pressure. The abrupt increase at about 35 km, however, would suggest a change in composition. Figure 8.18 shows that mafic igneous rock (e.g., basalt) has higher seismic velocities than felsic rocks (e.g., granite).
You might also like to view...
Though we don't generally think of it when we talk about globalization, a world economy has been in existence for
A) millions of years. B) thousands of years. C) centuries. D) decades. E) years.
The mountain building event associated with intracratonic uplift in western North America
during the Late Paleozoic produced the _______________. Fill in the blank(s) with the appropriate word(s).
Because air temperatures normally decrease with increasing height, trees found on the cooler north-facing side of mountains are often those that usually grow
a. ?at lower elevations. b. ?near the Arctic circle. c. ?in arid climates. d. ?near the equator. e. ?at higher elevations.
Use the following example:A species can withstand a narrow range of temperature. Above 100°F there are no species present. In the range from 97°F to 100°F and 90°F to 94°F there are a few species present. Below 90°F there are no species present.What would you label the range of temperature from 95°F to 96°F for this particular species in the scenario?
A. Optimal range B. Range of tolerance C. Zone of physiological stress D. Zone of intolerance E. Tolerance limit range