Passage II

Mass movement is the movement of soil or rock down a slope. Two types of mass movement are soil creep and block glide (see Figure 1).

Scientists studied soil creep at 3 sites (Sites 1-3) and block glide at 3 other sites (Sites 4-6) in a particular region. Beginning on March 1, 1995, and every 6 months thereafter until September 1, 1998, the scientists measured the cumulative distance that material at the surface had moved since September 1, 1994. Figures 2 and 3 show the results for Sites 1-3 and for Sites 4-6, respectively. Each figure shows the amount of precipitation that fell at each of the 3 sites over each 6 month period.

Figures 2 and 3 adapted from D. N. Swanston, R. R, Ziemer, and R. J. Janda, "Rate and Mechanics of Progressive Hillslope Failure in the Redwood Creek Basin, Northwestern California." U,S. Geological Survey Professional Paper 1454-E, 1995.

10. Consider in Figure 2 the 6-month periods during which there was no soil creep at any of Sites 1-3. During those periods, the amount of precipitation that fell at each of the sites was:

Answer and Explanation

Your Answer is

Correct Answer is F

Explanation

The question stem mentions 6 month period...no soil creep at any of Sites..., so when the slope of the three line segments in figure 2 is 0, that is, during the period of Mar. 1,1996-Sept. 1,1996, Looking at the ordinate on the right, the corresponding precipitation during this period is about 200 mm.