TOPOGRAPHIC MAP EXERCISE

GEOL 101

Topographic Map Lab

Created originally by Tom Braziunas, modified and used with permission.

Introduction

A topographic map is a precise, graphic representation of the three-dimensional shape of the earth's surface.

A standard topographic map uses contour lines to express elevations above sea level and show the shape of the land. A topographic map may or may not include shaded relief to help visualize steep slopes.

Topographic maps are used by surveyors, engineers, land and natural resource managers, and geologists, as well as hikers, backpackers, and other outdoor recreationalists.

Outcomes

A topographic map is a precise, graphic representation of the three-dimensional shape of the earth's surface.

A standard topographic map uses contour lines to express elevations above sea level and show the shape of the land. A topographic map may or may not include shaded relief to help visualize steep slopes.

Topographic maps are used by surveyors, engineers, land managers, natural resource managers, and geologists, as well as hikers, backpackers, and other outdoor recreationalists.

What You Need to Know Beforehand

what latitude and longitude are

how to write record latitude and longitude correctly as units

the requirement of stating, as part of the units, whether latitudes are N or S (and what N and S stand for)

the requirement of stating, as part of the units, whether longitudes are E or W (and what E and S stand for)

how latitude and longitude are traditionally written in degrees, minutes, and seconds (symbolized respectively as , ', and ") though if need be they can be converted to decimal degrees (which use tenths, hundredths, etc. after a decimal point)

how the Township and Range grid and numbered sections of approximately one square mile each are used on standard United States topographic maps

how to find and refer to locations on the map using Section, Township and Range

the two types of scales used on standard topographic maps

how to measure distances on a map using the map scale, in combination with a ruler and/or the edge of a piece of paper

what a contour line is

what the rules are for contour lines

how the rules make sense once you understand the definition of a contour line

how to use a map legend (list of symbols) to look up what the symbols on a map mean

II. Virtual Lessons

The United States is not the only country to rely on topographic maps. Can you spot the Great Pyramid of Cheops on the Egyptian topographic map above? (image from the US Library of Congress)

To learn what you need to know going into this lab, here are some Web resources for topographic maps:

Mark McNaught at Mt, Union College in Alliance, Ohio has a good introduction to reading topographic maps, at Mark's Topographic Map Tutorial: http://raider.muc.edu/~mcnaugma/Topographic Maps/topomapindexpage.htm#Menu.

The United States Geological Survey, your taxpayer-supported source of most topographic map data and topographic and geologic maps in the United States, give you an introduction to topographic maps and how to read them, including standard map symbols, at USGS Mapping Program/Topographic Map Symbols/Reading Topographic Maps: http://egsc.usgs.gov/isb/pubs/booklets/symbols/reading.html.

In addition, here are a couple other possibly useful web sites for you to use:

Berkeley Library Map Web Site

"About.com" for searchable information on geologic features on maps

III. Online Map Exercises

You can click on the images to view them in a separate browser window.

CARKEEK PARK QUESTIONS #1 - 4:

To the left is a small portion of a topographic map showing a road and a creek (blue-green line) in Carkeek Park in Seattle. North is always toward the top of topographic maps such as this.
Q.1: Using the "Rule of V's" determine which way is the creek flowing.
     a. north-to-south
     b. south-to-north
     c. east-to-west
     d. west-to-east

Hint: You will find the section on "Streams and Stream Valleys" in Mark's Map Tutorial to be especially helpful for deciding which way the creek is flowing.

Q.2: What do the little black boxes denote?
     a. bench mark
     b. small park, reservation, or monument
     c. quarry or open pit mine
     d. building

Hint: There is a guide to "Topographic map symbols" on the USGS website mentioned above. These squares don't represent gas wells but instead are the same as the rectangles in the guide.

More of Carkeek Park is displayed on the portion of topographic map shown below. Note that every fourth contour line is heavier and labeled with heights in feet (these heavier lines are "index contours"). The spacing between adjacent contour lines (all contour lines including the lighter ones) is called the "contour interval".

Q.3: What is the contour interval of this map?
     a. 10 feet
     b. 25 feet
     c. 50 feet
     d. 100 feet
      Hint: Carefully count the number of contour lines between index contours.

Q.4: What is the elevation difference between the two red arrows?
     a. 10 feet
     b. 25 feet
     c. 50 feet
     d. 100 feet

GREEN LAKE QUESTIONS #5 - 6:

The contour interval on this map is 25 feet.

Q.5: What is the approximate elevation of Green Lake?
     a. 75-100 feet
     b. 100-125 feet
     c. 125-150 feet
     d. 150-175 feet

Hint: Find the closest contour line and determine its elevation. The lake level must be BELOW that contour line's elevation but ABOVE the next lower contour elevation.

Q.6: Which corner of the map shows the highest elevation?
     a. northeast
     b. northwest
     c. southeast
     d. southwest

Hint: Look for the index contour line closest to the corner and then determine the elevation of thee contour line in the very corner. The corner itself must be ABOVE that contour line's elevation but BELOW the next higher contour elevation.

BLAKE ISLAND QUESTION #7:

The next map shows Blake Island in Puget Sound. By now, you have learned how to read that the highest point on Blake Island is between 250 and 275 feet. The contour interval of the map is 25 feet and the index contours are every 100 feet. The numbers "25" and "36" are related to the Public Land Survey System. The next two maps will illustrate some additional interpretations of contour lines.

Q.7: From which direction would it be easiest to climb from the shore to the top of Blake Island?
    a. From the Northwest
     b. From the Southwest
     c. From the Southeast
     d. From the Northeast

GRAND CANYON QUESTIONS #8 - 9:

This topographic map shows the Isis Temple, a high-elevation (7012 foot) butte in the Grand Canyon. You will notice that the contour lines are closer at some elevations (the steep cliffs) and more broadly spaced at other elevations (the gentler slopes).

Q.8: What is the contour interval, and how far apart are "index contours"?
     a. contour interval-5 feet, index contours-25 feet
     b. contour interval-10 feet, index contours-50 feet
     c. contour interval-25 feet, index contours- 125 feet
     d. contour interval-80 feet, index contours-400 feet

     Hint: Remember that the contour interval is the elevation difference between contour lines.
             The "index contours" are the darker, labeled ones.

Q.9: Approaching from the south, the steepest cliff occurs between which adjacent INDEX contours?
     a. 4800 and 5200 feet
     b. 4400 and 4800 feet
     c. 4000 and 4400 feet
     d. 3600 and 4000 feet

FLORIDA QUESTION #10:

This map shows a sinkhole region in Florida. Note that hachure marks mean that the contour lines drop in elevation instead of rise. Some of these sinkholes are deep enough to be filled with water to become lakes.

Q.10: What is the contour interval, and how far apart are the "index contours"?
     a. contour interval-5 feet, index contours-25 feet
     b. contour interval-10 feet, index contours-50 feet
     c. contour interval-25 feet, index contours- 125 feet
     d. contour interval-80 feet, index contours-400 feet

REMAINING QUESTIONS BASED ON AN ACTUAL, PRINTED TOPOGRAPHIC MAP:

Your instructor will have loaned you a topographic map, in which case DO NOT write or draw on the map, and do not fold it.

Alternatively, you may have been given instructions on how you are to acquire a specific topographic map for yourself, and you will have acquired it as instructed.

Q.11: What is the name of the quadrangle map that you are working with?

Q.12: What size quadrangle is the topographic map?
     a. 60 minute
     b. 30 minute
     c. 15 minute
     d. 7.5 minute

Q.13: What fraction of a degree of latitude does the map quadrangle span? (Hint: Divide your answer to the previous question by the number of arc minutes in a degree.)
     a. one whole degree of latitude
     b. one half of a degree of latitude
     c. one fourth of a degree of latitude
     d. one eighth of a degree of latitude

Q.14: What fraction of a degree of longitude does the map quadrangle span?
     a. one whole degree of longitude
     b. one half of a degree of longitude
     c. one fourth of a degree of longitude
     d. one eighth of a degree of longitude

Q.15: What is the latitude of the northern boundary of the map? (Remember that when writing latitudes, you must write N after the degrees, minutes and seconds if it is in the Northern Hemisphere, or S if it is in the Southern Hemisphere.)

Q.16: What is the latitude of the northern boundary of the map?

Q.17: What longitude is the eastern boundary of the Mt. Adams map? (When writing longitudes, you must write E after the degrees, minutes and seconds if it is in the Eastern Hemisphere, W if it is in the Western Hemisphere.)

Q.18: Based on your answers above, which is a true statement?
     a. The quadrangle is in the northern hemisphere and the western hemisphere.
     b. The quadrangle is in the northern hemisphere and the eastern hemisphere.
     c. The quadrangle is in the southern hemisphere and the western hemisphere.
     d. The quadrangle is in the southern hemisphere and the eastern hemisphere.
     e. None of the above can be determined with just this map.

Q.19: What is the fractional scale on the map? (It is expressed as 1:XXXX, where your answer is the correct number for XXXX. You can think of it as 1 inch on the map represents XXXX inches in the real world.)

Q.20: Based on your answer to question 17, one inch on the map represents how many miles in the real world? As always when asked to calculate, show your calculations!

(Hint: Divide the XXXX number from the previous answer into the number of inches in a mile. The number of inches in a mile is 12 times the number of feet in a mile.)

Q.21: What was the magnetic declination of the map at the time it was published?

(Remember to state not only the number of degrees but whether magnetic north was east of true north or west of true north.)


Q.22: If you were interested in the land just to the southeast of the map, which topographic quadrangle map would you get?

Q.23: What is the contour interval for the map?

Q.24: What is the index contour interval (the contour interval between index contours) on the map?

Q.25:   What is the highest elevation labeled for a peak or hilltop on the map?

Q.26: What is the latitude of that highest altitude labeled point on the map?

State the answer in degrees, minutes, and seconds as precisely as you can determine it.

Q.27: What is the lowest elevation on the map?

Hint: It may be lower than lowest labeled elevation, in which case you should write "The lowest elevation on the map is lower than _____ (the last contour line before that point on the map) and higher than _____ (the elevation of what would be the next contour line down in elevation, which is not seen on the map.

Q.28 (a): Does your map have sections labeled in red numerals, such as section 5 or section 28?
        (b) If it does, what is the approximate distance across each section?



Q. 29: How many sections are there in each township and range?

Hint: A township is six sections across, and so is a range. Multiply.

Q.30 (a): What is the definition of a contour line?

Q. 30 (b): What color are the contours on your topographic map?