1. Topographic Maps
TOPOGRAPHIC
MAPS

2. What are topographic maps?
Topographic maps- maps that show changes in elevation of Earth’s surface
Elevation- distance above sea level.
Also show mountains, rivers, forests and bridges
TA asks Ss to recall what elevation is (just discussed) Elevation is the height above sea level on the Earth’s surface.

3. Contour Lines Contour lines- connects points of equal elevation.
TA asks students Is it possible for contour lines to cross? EA NO
If students say yes. Ask them how that would be possible if each line represents an elevation. Can one point have two elevations? No!

4. One Island….Two Views
TA asks Ss: Which map shows the view that you would see if you were a ship sailing offshore of the island? EA: the one on the left.
What would the map on the right represent? EA: the overhead view.
Which map is able to show us more about the changing elevation of the island? EA: The one on the left
Using what you’ve learned from the activity and topographic maps, how do you think we could modify the map on the right to show us more about the topography of the island? EA add contour lines.
What information would we need to add contour lines? EA: Elevation at different points.

5. One Island…Two Views
Looking at each map how many high points do we see? Two
How are the high points represented on the map? Small closed circles

6. Identify the Elevation
TA asks Ss What is the elevation at point A? EA 0 ft
If elevation is a measure of distance above sea level what does an elevation of 0 ft tell us? EA we’re at sea level
What is the difference in elevation between point A and point B? EA 10 ft.
What is the distance between each consecutive contour line? 10 ft

7. What is a contour interval?
Contour interval- the difference in elevation between two side by side contour lines
What is the difference in elevation between these two lines?
TA asks Ss. In the picture below how can we figure out the contour interval? What information will help us? EA the numbers. The numbers that are listed on the contour lines are known as Index Contours. Index contours just tell us the elevation at a certain contour.
How can we use this information to help us determine the contour interval? Count the number of lines in between (count the one we start on, but don’t start the one we finish on) the two, find out the total elevation between them, then divide.
What is the contour interval? 20 ft.

8. What are index contours?
Index Contours- contour lines that have marked elevations.
Can use them to find the contour interval
Index Contours
TA asks Ss. In the picture below how can we figure out the contour interval? What information will help us? EA the numbers. The numbers that are listed on the contour lines are known as Index Contours. Index contours just tell us the elevation at a certain contour.
How can we use this information to help us determine the contour interval? Count the number of lines in between (count the one we start on, but don’t start the one we finish on) the two, find out the total elevation between them, then divide.
What is the contour interval? 20 ft.

9. Finding the Contour Interval
Find the index contours.
Determine the elevation difference between the two index contours
800 m – 700m = 100 m
3. Count the number of spaces between the 2 index contours. 5
4. Divide the elevation difference between the 2 index contours by the number of spaces.
100 m / 5 = 20 m.

10. Scale
Scale is the relationship between horizontal distance on the map and distance on the ground.

11. Three types of scale

12. Three types of scale

13. Three types of scale

14. Do Worksheet 1-6
Contour mapping rules

15. 1. A contour line represents a single equal elevation, all points on the contour line have the same elevation.
What is the elevation of point B? 10 What would the elevation of any point on that line be? 10

16. 2. Contour lines do not cross other contour lines.

17. 3. Where one closed contour line surrounds another, the inner contour line represents the higher elevation.
Which line has the higher elevation?

18. 4. Every 5th contour line is darker and has the elevation marked
4. Every 5th contour line is darker and has the elevation marked. These are index contours.

19. What is slope?
Slope- change in elevation over a given horizontal distance
Formula for slope
Slope = change in elevation
horizontal distance
Which hill has a steep slope?
Gentle slope?

20. 5a. On a contour map, closely spaced lines indicate a steep slope.

21. 5b. Widely spaced lines indicate a gentle slope

22. 5c. Uniformly spaced lines indicate a uniform (constant) slope.
Notice that the contour lines for each are the same distance apart in each picture. There is the same change in elevation for each given distance.

23. Comparing Slope

24. 6. A contour line that closes within the limits of a map indicates a hill, ridge or plateau.

25. 6a. Highest possible elevation of a hill is just below the value of the next contour line that would be drawn.
The highest elevation of a hill can be calculated by finding the last (highest) contour line on that hill, and then figuring out the next line that would be drawn. The highest possible elevation of the hill is just below the value of  that next line. The highest possible elevation of the hill indicated by the arrow is 239 meters.
The last line indicated on the map is 220 meters. The next line would be 240 meters (remember that the contour interval is 20 meters). Since there is no 240 meter line, the hill cannot be higher than 239 meters!
The last contour line drawn is 220 m. The next line would be 240 m. Since there is no 240 m line, the hill cannot be higher than 239 m.

26. 7. Depressions are shown by small marks (hachures) pointing inward off the contour line.
When would you see an area were the elevation is lower than surrounding areas? EA: craters, mines, volcanic craters
What would the elevation of the last contour line drawn be? 140 m
The hachures have the same elevation as the last contour line.
The depression is less than the last contour line, but not as small as the contour line before it.
Elevation of the depression would be between 140 and 120 m.
Elevation of the depression would be
less than 140 m.

27. 8. Where a contour line crosses a stream or valley, the contour bends to form a “V” to point upstream.
Which direction is the river flowing? Towards the ocean, NE
Contour lines will always bend to point upstream, toward the soruce of the river.
Rivers flow from upstream to downstream, toward the mouth of the river.
Since contour lines must remain at the same elevation, they must bend when they cross riverbeds. A riverbed drops downward, so the contour line must bend uphill to stay at the same elevation. The highlighted lines show that the direction of the Mill River must be northeast.

28. Exit Card
Without looking at your notes, write two things you learned today. Write one question you have about topographic maps. It can be something that confused you or something you’d like more information about.

29. There can be several answers to this. Let’s say Mt. Tim, Mt
There can be several answers to this. Let’s say Mt. Tim, Mt. Tom, Woodland and Valley represent exact points on the map. Tell me the elevation at Mt. Tom? (ANS: 800’<TOM<900’) Mt. Tim? (ANS: 700’<TIM<800’) Valley? (ANS: 600’<VAL<700’) Woodland? (ANS: 600’<WOOD<700’) Why is that correct?