1. Show the shape of the Earth’s surface.
Topographic Maps
Show the shape of the Earth’s surface.
Allen, Spring '04

2. A topographic map of part of Ithaca

4.  List three situations when you might use a topographic map instead of a road map.

5. Contour Lines As contour lines become further apart…
The gradient decreases – not steep
As contour lines become more closely spaced…
The gradient increases - steep

6. Contour Lines
Closed contours appearing on a map as ellipses or circles represent hills or knolls
Closed contours with hachures represent depressions

7. What is the pattern of the contour lines around a simple hill?
Concentric circles getting smaller - hill

8. Identify the features marked at A and B

9. Hachure contour lines (lines with tick marks) show depressions – the first hachure is equal to the last contour line passed 20 20 10

10. WHAT DOES THIS PROFILE SHOW?
VOLCANO
NOTICE HACHURE DEPRESSION LINES IN CENTER SHOWING VOLCANIC VENT

11. Contour Lines Contour lines don’t cross each other
Although at a vertical cliff they may be on top of one another
Where contour lines cross streams and rivers they have a v-shape and the v points upstream

12. Contour Interval
The elevation change between contour lines is the Contour Interval
The vertical distance that separates each contour line on a topographic map
The contour interval is stated on each map

13. Contour Interval
 What is the contour interval on this map?

14.  What might you use index contours for?
Index Contour Lines
These are heavy lines spaced at predetermined elevations on a topographic map
Are usually labeled with a number somewhere along the line
 What might you use index contours for?

15. Index contour lines are placed every 50 units on this map

16.  What is the spacing of Index Contours on this map?
 What is the contour interval?

17. Map Symbols
The United States Geological Survey (USGS) uses the same map symbols on every map.
Most USGS maps do not have a key – you need to provide your own!

18. Colors on Topographic Maps
Blue stands for water
Green stands for forested areas or woods
Green dots lined up in rows show an orchard
Black is human-made structures
Pink stands for high population areas
White stands for non-wooded areas
Red represents for highways
Brown indicates contour lines

19. Map Scale
The relationship between distance as measured on a map and the actual distance on Earth’s surface
One of any unit on this map represents 24,000 of the same unit on Earth’ s surface

20. Maps often give you more than one way to measure distance
Represents one mile on the map
Represents parts of one mile, ex: one tenth of a mile
One kilometer

21. Known Elevations
Places of known elevation are shown with the abbreviation “BM”
BM stands for benchmark
An “X” and elevation number might appear with the BM
BM, X and the elevation are written in BLACK
Benchmarks are set in concrete and checked periodically by the USGS

22. This is what a Benchmark looks like.
Extra Credit: bring in a “rubbing” from a local benchmark.

23. Maximum Elevation of a Hill
Steps to follow:
1. Count up the contour lines using the contour interval.
2. Pretend that there is one more contour line at the top of the hill (imaginary line).
3. Subtract 1

25. Notice line AB

26. So, if we were to look at a profile view of line AB on our topographic map, what might we expect to see? Predictions?
Time to FIND OUT!
Step 2

27. Take out a piece of scrap paper

28. Make a small tick at A and B

30. Make a small tick where each contour line crosses AB

32. Label each tick mark with the correct value!

33. Make the X-axis exactly as long as line AB.

34. Next, decide what the HIGHEST and LOWEST elevation values are that line AB crosses on your topographic map and create a scale. You may wish to increase your scale by the contour interval on the map to make things easier. In this case, we are going up by 10’s, because our contour interval on the map is 10 meters.

35. Remember Labels and Units!

36. Hold your scrap paper page up to the profile.

37. Transfer the tick marks directly onto the profile.

39. straight edge may help

42. connect the dots!

43. This is what you might expect the “profile” or cross section view of line AB to look like!
Notice how the line dips below 250m where it crosses Long Creek

44. Does it make sense. SURE. There is a creek flowing through this region
Does it make sense? SURE! There is a creek flowing through this region. Think about where it would flow on your profile. We also recognize the V shaped contour lines that indicate the direction of water flow.

45. The contour lines point up the page (orange), but Long Creek flows down the page.

46. Contour lines point upstream
Contour lines point upstream. Stream flows from high elevation to low elevation. So a stream flows in the oppostite direction the contours point.

47. CONTOUR LINES BEND WHEN CROSS STREAMS
UPSIDE DOWN V’S POINT UPSTREAM STREAMS FLOW DOWN