What is purpose of a topo map?

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1 Topographic Mapping 8.9C Interpret topographical maps and satellite views to identify land and erosional features and predict how these shapes may be reshaped by weathering

2 What is purpose of a topo map? They show the surface features of an area Topographic maps add a third dimension to latitude and longitude by showing natural (and cultural) features of the earth s surface in particular, elevation.

3 Texas Historically, mapmakers used a variety of methods to indicate elevation. To get a quick sense of elevation, we can use color, as in this map.

4 Using Color vs. Contour Lines This method of showing elevation wouldn t help much for a close-up map, though say, for hiking or roadbuilding. For simplicity, clarity, and accuracy, most topographic maps today use contour lines.

5 Contour Lines Contouring is drawing lines on a two-dimensional grid of numbers that connect points of equal value. In the following grid, for example, The drawn contour lines connect multiples of 10, so we d say that the contour interval the space between the lines is 10:

6 More complicated example: Here s a more complicated one can you see the hills and plains? Plains Hill The contour lines on a topographic map show lines of constant elevation, so it s easy to see hills, valleys, and plains, and the lines are usually labeled with their elevation.

7 Contour Lines Contour Lines are imaginary lines that join points of equal elevation above or below sea level That s right we have even mapped under the ocean!

8 Contour Lines Equal elevation Follow any given line from one side to the other. This continuous line indicates equal elevation.

9 Rules of Contour Lines Never cross each other Connect with themselves Get closer together as land gets steeper Get further apart as land gets flatter

10 Contour Interval The change in elevation from contour line to contour line is called the contour interval The distance that separates contour intervals

11 Connecting Lines practice! You should have 2 copies of this grid. Try different contour intervals (5 and 10, say) and see how it affects the finished picture. What geographical features seem to appear? Which are more or less prominent depending on the contour interval?

Learning to read topo maps Learning to use a topographic map is a difficult skill, because it requires students to visualize a three-dimensional

12 Learning to read topo maps Learning to use a topographic map is a difficult skill, because it requires students to visualize a three-dimensional surface from a flat piece of paper. Land Features and other objects are also indicated on a topo map Topographical map symbols can be found online:

13 Land Features - Depression

14 Land Feature - Valley

15 Land feature - Ridge

16 Land Feature - Hill

17 Tracking Flowing Water How does water always flow? DOWNHILL How can we tell what direction (N,S,NW,ESE) is downhill? PSC 121 Prince George's Community

18 Tracking Flowing Water You can look for elevation changes since water will flow from higher to lower elevations. Here the stream flows toward the northwest ft 2100 ft

19 Tracking Flowing Water You can look at the contour lines as they cross the stream. They will always point upstream. Downstream Upstream PSC 121 PRINCE GEORGE'S COMMUNITY COLLEGE

20 Tracking Flowing Water You can also look at where two streams merge. The merge will form a V that points downstream. Direction of flow PSC 121 PRINCE GEORGE'S COMMUNITY COLLEGE

21 Where erosion may occur a stream would run down the middle or side of the V s this is the most likely place where erosion would occur. Over time, this could change the landscape

22 Gradient The gradient of a mountainside is a measure of its steepness.

23 Relief The relief of a contour map is the difference between its highest and lowest points. Contour interval 50m

24 Contours and Profiles You can generate a profile of a landform from the contour lines on a topographic map. Simple contour map

25 Colorado Notice not only how many lines there are, but how shown on a computer the impression of elevation can be added

26 Nebraska This is a satellite topo map. It uses color and shaping to indicate elevation. Notice Nebraska versus heading west - see all of the mountains?

27 Put yourself in a map!

28 Let s take a walk up a hill!

29 We re now at an elevation of 100 meters. 100m

30 We re on the peak, but what s our elevation? 300m 200m 100m

31 Can we get more precise? Let s add contour lines for every 50 meters and see if that helps. 300m 200m 100m

32 We know that we are above 350m, but less than 400m. 350m 300m 250m 200m 150m 100m 50m

33 Time to go home - Now what s our elevation? If you said somewhere between 200m and 250m you are right! 350m 300m 250m 200m 150m 100m 50m

34 Let s now look at the same hill, but the way we might see it from an airplane!

35 Each color change represents a 50 meter increase.

36 Now, let s try the same hike! Our elevation is 0 meters.

37 Now what is our elevation?

38 If you said more than 150 meters, but less than 200 meters you re right!

39 Let s go a little higher.

40 Think you know our elevation now? More than 300 meters But less than 350meters

41 More on Satellite Views Satellite views can be used to learn about erosion and how the land has changed images taken over time can be used for comparison and interpretation of erosional features (ex. after a flood)

42 Reminder of key terms! Weathering is the breaking down of rocks, soil and minerals Erosion a process (such as water flow or wind) which removes soil and rock from one location on the Earth's crust, then moves it Deposition the location where freshly eroded material gets placed

43 Let s see what you know. E C D A B 1200m 1000m F 600m 800m

44 1. Could the elevation at the peak (B) be 1410 meters? No :The elevation must be under 1400 meters, but over 1300 meters. E C D A B 1200m 1000m F 600m 800m

45 2. What is the elevation at (E)? About 400 meters E C D A B 1200m 1000m F 600m 800m

46 3. If you walked a straight line from (D) to (C) would you walk over a ridge or down a valley? Down a valley: If the contour lines point up the slope it s a valley, if they point down the slope it s a ridge. E C D A B 1200m 1000m F 600m 800m

47 S 4. Just looking at the map, would it be easier to head down from the peak going East, or going North? East: When contour lines are close together that means there is a steep slope, the further apart the lines, the more gentle the slope and therefore an easier walk! Go N east! E C W D A B 1200m 1000m F E 600m 800m

48 Contour Practice 1. What is the contour interval of the map at left? 80 m 2.What is the elevation of point A? 320 m 3. What is the elevation of point B? 880 m 4.What is the elevation change between A and B? 560 m 5.If the horizontal distance between point A and point B is 2.8 km, what is the gradient? 200 m/km

49 Make a Mountain!

50 Supplies: 1. Ruler 2. Playdoh 3. String 4. Wax paper Follow instructions on the page to build and map your own mountain!

51 Close to Home Local maps &s=50&name=Enchanted%20Rock Topo Map -

Map Patterns and Finding the Strike and Dip from a Mapped Outcrop of a Planar Surface

Map Patterns and Finding the Strike and Dip from a Mapped Outcrop of a Planar Surface Topographic maps represent the complex curves of earth s surface with contour lines that represent the intersection