40 80 120 160 Well water level (feet below land surface) Land surface 0 Well water level 0 2 200 8 240 Santa Clara Valley Ground 10 subsidence 280 12 320 14 1910 1920 1930 1940 1950 1960 1970 Year A Figure 8.16 Ground subsidence and changing water levels in a well in the Santa Clara Valley, California. (Courtesy of U.S. Geological Survey) Ground subsidence (feet) EM 645 850 Grove O LOUISVILLE BM 585 Oslo Well Off Wells Oil Wells BM637 Fairview FIGURE 8.18 Park City, KY 1/4 .5 1/2 Creek 577 Cem Cerp 585 NASHVILLE BM AND 615 2 kilometers North 1 1 mile SCALE: 1:24,000 Well EDMONSON CO BARREN CO Woodland Ch Apple Grover Cave 3la BM 635 Well Wells COMBERLAND 651- BM 726 Mt Vernin
PART 1 Activity 8.7 Ground Subsidence (Figure 8.7)
1. What is the general relationship between ground subsidence and the level of water in the well?
2. What was the total ground subsidence, and what was the total drop in the level of water in the well during the period shown on the graph?
Total ground subsidence: —--feet
Total drop in well level: —-- feet
3. During the period shown on the graph, on aver-age, about how much land subsidence occurred with each 20-foot decrease in the water level in the well: 1 foot, 5 feet, or 10 feet?
Subsidence: about—----foot/feet
4. Was the ground subsidence that occurred between 1930 and 1950 less or more than the subsidence that occurred between 1950 and 1970?
Ground subsidence from 1930 to 1950 was—----than that from 1950 to 1970.
5. Notice that minimal subsidence occurred from 1935 to 1950. Refer to the well water level during the same period of time and suggest a possible reason for the reduced rate of subsidence.
PART 2 Activity 8.8 Examining a Karst Landscape (Figure 8.18 and Figure 8.19, I can only upload two images so if you have figure 8.19 in applications and investigations in earth science 9th edition, it would help a lot.)
1. Locate three sinkholes (depressions) on the map and mark each with an X. (Hint: Look for closed contour lines with hachures.)
2. Notice that several sinkholes have water in them. What does this indicate about the depth of the water table in this area?
3. Describe what is happening to Gardner Creek in the area indicated with the letter A on the map.
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