STONE MOUNTAIN TOPOGRAPHIC MAP EXERCISE

Pamela J. W. Gore, 1994, 1998

Georgia Perimeter College

This laboratory exercise requires the following two maps:

STONE MOUNTAIN QUADRANGLE, GEORGIA 1:24,000 (1992)

You will need to consult a Georgia highway map of to answer questions 34B, 35 and 36.

1. What is the latitude of the line which bounds the northern edge of the map?

2. What is the latitude of the line which bounds the southern edge of this map?

3. How many degrees of latitude are covered by this map? (Subtract #1 - #2)

4. What is the longitude of the line which bounds the western edge of this map?

5. What is the longitude of the line which bounds the eastern edge of this map?

6. How many degrees of longitude are covered by this map? (Subtract #4 - #5)

7. How many miles are covered by this map in a north-south direction? (Use the scale at the bottom of the map.)

8. How many miles are covered by this map in an east-west direction? (Use the scale at the bottom of the map.)

9. What is the area in square miles covered by this map? (Multiply length in miles x width in miles = area in mi2)

10. How many kilometers are covered by this map in a north-south direction? (Use the scale at the bottom of the map.)

11. How many kilometers are covered by this map in an east-west direction? (Use the scale at the bottom of the map.)

12. What is the area in square kilometers covered by this map? (Multiply length in km x width in km = area in km2)

13. What is the contour interval of this map? (Look in the bottom margin of the map.)

14. Locate Georgia Perimeter College (formerly DeKalb College) on the map. Give its coordinates in terms of latitude and longitude.

15. Does the new Georgia Perimeter College library appear on the map? Why not?

16. What is the elevation of the contour line which passes through the area where the new library is located?

17. What does the green color on the map indicate?

18. What does the gray color on the map indicate? (See the lower margin of the map.)

19. What does the black color on the map indicate?

20. What does the blue color on the map indicate?

21. What does the brown color on the map indicate?

22. What does the red color on the map indicate?

23. Locate the north arrow in the lower margin of the map. Note that there are "three norths" - (1) MN or magnetic north (where your compass points), (2) the star, indicating Polaris which lies on the celestial sphere above the Earth's north rotational axis - "true north", and (3) GN which relates to the Universal Transverse Mercator (UTM) grid system - the fine black grid lines that run north-south and east-west on the map every inch and a half or so.

Are the UTM grid lines parallel with the latitude and longitude lines?

24. In which compass direction is the City of Atlanta with respect to this map?

25. What counties are covered in part by this map?

26. a. Where is the highest point on this map? (Hint, there is a beacon there.)

b. What the elevation at the top of the highest point?

27. What is the amount of relief of Stone Mountain? _________________

Elevation at the top minus elevation at the bottom (use the benchmark on the north side).

28. Where (in general) would you find the lowest elevation(s) on this map, and why?

29. How can you determine that Stone Mountain Lake (and most of the other lakes on this map) is man-made? (Carefully observe the downstream end of the lake. What map feature do you see?)

30. Which side of Stone Mountain is steepest? (Give compass direction.)

31. Determine the angle of slope of the steepest side of Stone Mountain. You can do this using trigonometry or you can do this graphically by plotting on graph paper the vertical change in elevation over a certain horizontal distance. Procedure:

(1) Take a piece of scratch paper with a straight edge, and lay it along the bar scale at the bottom of the map. Using a pencil, mark on the straight edge of your scrap of paper an interval of 600 feet. (Put a mark at 0 and a mark at 600 feet). You will use this as your horizontal distance.

(2) Place your piece of paper (with the 600 ft interval marked) on the steepest side of the mountain, oriented perpendicular to the contour lines. One end will be toward the base of the mountain, and the other end will be toward the top of the mountain. So that we can all be consistent, place your paper along the cable car route. Put the "0" end of the paper on the heavy index contour line at the base of the mountain.

(3) Determine the elevation of the index contour at the base of the mountain. ______________ feet

(4) Determine the elevation of the contour line at the upper end of your piece of paper (at the 600 ft mark). ______________ feet

(5) Subtract the elevations you found to determine how much vertical change in elevation occurs over a horizontal distance of 600 feet. ______________ feet

(6) Determine the angle of slope of the mountain side.
To do this trigonometrically, tan a = vertical change in elevation/horizontal distance.
To do this graphically, you will need to get a piece of graph paper and draw a right triangle whose sides are proportional in length to the numbers you have determined.

How do you draw the triangle? Let the base be 6 inches long (6 inches is proportional to 600 feet), and let the height be similarly proportional to the vertical change in elevation - i.e., if your vertical change in elevation is 400 ft, the height of your right triangle will be 4 inches; or if the vertical change is 560 feet, the height of your triangle will be 5.6 inches). Once you have drawn the horizontal and vertical sides to your triangle, draw in the hypotenuse. (STAPLE YOUR TRIANGLE TO THIS LAB AND TURN IT IN.)

(7) Once you have drawn your triangle, use your protractor to measure the angle of slope of the side of the mountain (with respect to the horizontal).

___________________ degrees

32. Repeat the above procedure to find the slope of the gentlest (least steep) side of the mountain. So that we can all be consistent, please make your angle measurement along the walkup trail (the dashed line going up the western side of the mountain). You may wish to use a horizontal distance of 2000 feet instead of 600 feet).

Elevation at lower end = _______________ feet

Elevation at upper end = _______________ feet

Vertical change in elevation over 2000 feet horizontally = _______________ feet

Trigonometric determination of angle = ______________________ OR

Draw triangle (be sure to turn it in).

Angle of slope (as measured with protractor) = ______________ degrees

33. Find Clarkston.

a. What is the name of the stream that flows along the northwestern side of Clarkston?

b. In which compass direction does this stream flow?

c. Consult the Greater Atlanta Region topographic map. Into which stream (and ultimately, river) does this stream flow?

34. Locate the stream directly west of Georgia Perimeter College (behind Clarkston High School).

a. In which compass direction does this stream flow?

b. Consult a Georgia highway map. Into which streams (and ultimately, river) does this stream flow?

35. Does the Chatahoochee River ultimately flow into the Atlantic Ocean or into the Gulf of Mexico? (Look at a map of the State of Georgia to answer this question.)

36. Does the South River ultimately flow into the Atlantic Ocean or into the Gulf of Mexico?

37. Based on your answers to the above questions, you can see that Clarkston is located on a drainage divide. In other words, a drainage divide is a high area or ridge which separates streams that flow in different directions. On one side of Clarkston, the water drains into the Gulf of Mexico, and on the other side, the water drains into the Atlantic Ocean. This high area or ridge can be spotted readily on the map because the hill tops along this ridge are marked by contour lines which form circles.

You will note from careful observation of the map that a particular road in Clarkston runs along this drainage divide. A railroad track also runs along this drainage divide parallel with the road.

What is the name of the road? _____________________________________

From this, you can conclude that when it rains, the water which runs off one side of the road will end up in the Gulf of Mexico, and the water which runs off on the other side will end up in the Atlantic Ocean. The next time you drive down this road, take a look and think about this.

38. Follow this road and drainage divide on the map using your finger. Remember, if the road ever crosses a stream, it has left the drainage divide.

a. Does this road always follow the drainage divide? _______

b. If not, where does the road leave the drainage divide? (There is a benchmark there; what is its number)? ________

c. What road follows the drainage divide to the north?

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This page created by Pamela J. W. Gore
Georgia Perimeter College

August 31, 1998