Page 401 - Laboratory Manual in Physical Geology

A CTIVIT Y 14.2 Mojave Desert, Death Valley, California

Name: ____________________________ Course/Section: _____________________________ Date: ______________
Death Valley is located in the USGS 15-minute Furnace Creek, California quadrangle (provided on the back of this activity sheet).
It is the large valley (graben) in the middle of the map and the lowest valley in the United States ( FIGURES 14.2 , 14.3 ). Th e moun-

tains on each side of the valley are horsts ( FIGURE 14.7 ).

A. Obtain your set of colored pencils and do the following on the topographic map on the back of this page.
1. Neatly and precisely color alluvial fan A yellow, including the two arroyos at the top (upslope end) of the fan.

2. Color the inselbergs red in the vicinity of location B .

3. Color alluvial fan C yellow.
4. Color alluvial fan D yellow.

5. Color the 00 (sea level) topographic contours blue on both sides of the valley.

6. Make a green line along the downhill edge of the mountain front ( FIGURE 14.7 ) on both sides of the valley and label it

“mountain front.”

7. What is the elevation of the lowest contour line on the map? ______________ feet
8. What is the elevation of the lowest point on the map? ______________ feet

B. Notice the intermittent stream that drains from the upstream end of the alluvial fan/arroyo system A (that you have already

colored yellow) to the playa at E . How would the grain size of the sediments along this stream change as you walk downslope
from the high arroyo to the playa (E) ? Why?

C. The floor of most grabens is tilted, because fault movement is usually greater on one side of the graben than the other. There
are also half grabens, valleys developed along only one normal fault. Carefully examine the map on the back of this page for
evidence of faults on either or both sides of Death Valley. Draw a dark dashed line (with a normal pencil or a black colored
pencil or pen) wherever you think a normal fault may be present on either or both sides of the valley. Based on your work, do
you think that Death Valley is a graben or a half graben?

D. REFLECT & DISCUSS Notice that people chose to build a ranch on alluvial fan C , even though this entire region is

dryland. What do you think was the single most important reason why those people chose alluvial fan C for their ranch
instead of one of the other fans?

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