Guided Notes Topographic Maps Map scale Straight line distance Curved line distance Rules of Isolines Contour Lines Hachured Lines Possible elevations Slope & Gradient Direction of River Flow Topographic Profiles K. Coder 2015
2) How do you determine distance between points using a map? To determine distance between two locations on the map use the map scale. Map scale: the part of the map (usually at the bottom) that gives you distance in miles and/or kilometers If the map scale is in kilometers, the contour lines are elevations in meters. If the map scale is in miles, the contour lines are elevations in feet.
2) How do you determine distance between points using a map? There are two ways of determining distance: Straight line distance: determining the distance of a straight line drawn between two locations Curved line distance: determining the distance along a curved feature (road, tracks, trails, rivers)
2) How do you determine distance between points using a map? Straight Line Distance: To determine the distance between locations on a map, you will need a piece of scrap paper. 1. Place the scrap paper on the straight line between the two locations. You may have to use your imagination sometimes if the line is not drawn for you! 2. Make a mark on the edge of the scrap paper at the two locations. 3. Move the scrap paper to the map scale so that one of the marks is lined up with zero. 4. The other mark indicates the distance.
2) How do you determine distance between points using a map? Example: Determine the straight line distance between the given points using the map below. Points Distance 1) A and B 4 km
2) How do you determine distance between points using a map? Example: Determine the straight line distance between the given points using the map below. Points Distance 2) B and C 3.2 km
2) How do you determine distance between points using a map? Curved Line Distance: To determine the distance between locations on a map, you will need a piece of scrap paper. 1. Place the scrap paper on the straight line nearest your starting point. Mark the location of your starting point on the edge of the scrap paper. 2. Make a mark on the edge of the scrap paper where the first straight line distance ends. Make a mark on the map at this exact location. 3. Pivot your paper so that it lines up with the next straight line of the feature. Make a mark where this straight-line distance ends. 4. Continue this until you have reached your ending point. 5. Move the scrap paper to the map scale so that the starting point mark is lined up with zero 6. The ending point mark indicates the distance of the entire curved line.
2) How do you determine distance between points using a map?
2) How do you determine distance between points using a map? Example: Determine the length of the Green River from Point A to Point F on the map above. = 4km + 4km + 2.5km = 10.5 km 04 04 2.5 4 K. Coder 2015
Review Measuring Distances: 1. Using ESRT page 3 and a piece of scrap paper, determine the straight-line distance between the following two cities in both miles and kilometers. Note: each city is located at the point near the name of the city. Cities Kilometers Miles Elmira & Binghamton Syracuse & Oswego Ithaca & Utica
Checkpoint Measuring Distances: 2. A hiker is using the map below to plan his hike. What is the approximate distance along the trail between point C and D? Label your answer with the correct units. 0 3
3) How do we map fields? Isolines: a line that connects equal values in a field
3) How do we map fields? In Earth Science, we will spend a lot of time looking at three specific types of field maps: Elevation: contour lines connect equal elevations Temperature: isotherms connect equal temperatures Pressure: isobars connect equal pressures Other field maps we will see show snowfall, rainfall, volcanic ash, earthquake magnitudes, odor fluctuations, pollution concentrations
Isotherms on a Weather Map K. Coder 2015
Isobars on a Weather Map
4) How do we draw and read isolines? 1. All points on any one isoline have the same measured value.
4) How do we draw and read isolines? 2. All of the values on 1 side of the isoline are higher than the values of the isoline. All values on the other side of the isoline are lower in value than the isoline.
4) How do we draw and read isolines? 3. All isolines extend to the edge of a map unless they make a complete circle.
4) How do we draw and read isolines? 4. Isolines can never cross or touch each other.
4) How do we draw and read isolines? 5. Isolines tend to have gentle curves rather than sharp angles.
Checkpoint Reading Isolines Students in a class were told to draw the 22 and 24 value isoline on the maps provided. Some of the students made errors. Each map below is incorrect for one reason. Using the rules of isolines, explain why the map is incorrect.
Review Drawing Isolines Using a pencil, draw isolines with an interval of 1. Work neatly and carefully.
5) How is elevation shown on a map? Topographic (contour) map: a map that shows changes in the elevation of Earth s surfaces K. Coder 2015
5) How is elevation shown on a map? o Contour line: an isoline used on a topographic map to connect locations that have the same elevation (see lines on the bottom of this page). Contour line K. Coder 2015
5) How is elevation shown on a map? Figure 1. 3-dimensional landform from our perspective 2-dimensional topographic map of this landform (viewed from above) All elevations are measured above sea level, which has a value of zero.
5) How is elevation shown on a map? Figure 1. 3-dimensional landform from our perspective This landform must be in the ocean! 2-dimensional topographic map of this landform (viewed from above) The contour line that borders the ocean always has an elevation of zero feet or meters. (This does not apply to lakes and ponds.)
5) How is elevation shown on a map? Contour lines that are in the shape of circles indicate a hill or mountain peak. (see Figure 1) Figure 1. 3-dimensional landform from our perspective 2-dimensional topographic map of this landform (viewed from above)
5) How is elevation shown on a map? o Index lines: isolines that have their value labeled on them (frequently darker than the other isolines). Contour line Index line K. Coder 2015
6) How do you determine values of contour lines on a topographic map? Contour interval: this is the difference in value between isolines that are next to each other. o The contour interval on a map will never change.
6) How do you determine values of contour lines on a topographic map? Procedure for determining contour interval of a map: 1. Find the difference in value between index lines (subtract smaller # from larger #). Example: What is the contour interval on the map below? 20 meters 2. Divide difference between index lines by the number of spaces between the contour lines that are between the index lines. 80 40 meters = 40 meters 40 meters / 2 spaces = 20 meters Lake 80 40 Elevations in meters
Review Contour Interval: Use the topographic map below to answer questions
7) How can you determine possible elevations between contour lines? Possible elevations: locations in between contour lines can be estimated. o Elevations can be any value between the contour values (but cannot be equal to either of the contour values.
7) How can you determine possible elevations between contour lines? o Example: What are the possible elevations, in feet, of point X on the topographic map below? Any value from 21 to 39 feet Lake 40 20 X
8) How are depressions (or ditches) shows on contour maps? Hachured lines ( ): contour lines that indicate a depression in the ground. 290 290
8) How are depressions (or ditches) shows on contour maps? Rules for reading hachured lines: 1. The outer most hachured line is equal in elevation to the lower of the contour lines it is in between. 2. The elevation of any inner hachured line is equal to a decrease in elevation by the contour interval. Contour line it is between Contour interval = 10 290 Outer most hachured line Next hachured line 290
8) How are depressions (or ditches) shows on contour maps? Example: On the map below, what is the elevation of point E? 40 meters Hachured lines K. Coder 2015
Review Possible Elevations & Hachured Lines: 1. Use the topographic map below to answer the following questions. Elevations are in feet.
9) How are changes in slope shown on a topographic map? Slope: how quickly the elevation of the land changes K. Coder 2015
9) How are changes in slope shown on a topographic map? 1. The more closely spaced the contour lines are, the steeper the slope of the land. 2. The more widely spaced the contour line are, the more gentle the slope. Gentle slope Steep slope
10) How can the steepness of a slope be calculated? Gradient: how rapidly a field value changes over a particular distance. Field values: the value of what you are measuring that you plot on a map On a topographic map, the field values are elevations.
10) How can the steepness of a slope be calculated? Equation for gradient (found on ESRT front cover) Use isolines on map Use map scale
10) How can the steepness of a slope be calculated? Example Problem: Point A and point B are locations 0.24 mile apart on a ski slope in northern New York. Point A has an elevation of 1,560 feet and point B has an elevation of 1,800 feet. What is the gradient between these points? Show your work. Gradient = change in field value distance = 1800 1560 feet 0.24 miles = 240 feet 0.24 miles = 1000 feet/mile
Checkpoint Gradient: 1. Determine the gradient between point B and D on the map below. Show your work.
11) How can the direction of river flow be determined using a topographic map? River Flow Direction: 1. Rivers always flow downhill (from high elevation to low elevation).
11) How can the direction of river flow be determined using a topographic map? River Flow Direction: 2. Rivers always flow towards the ocean. K. Coder 2015
11) How can the direction of river flow be determined using a topographic map? River Flow Direction: 3. Rivers always flow in the opposite direction from which contour lines bend when they cross the river.
Notice how the contour lines bend when they cross the river. They point upstream, meaning the opposite way the river is flowing. Mt Marcy So. In which general direction is this river flowing? South/ Southwest! K. Coder 2015
11) How can the direction of river flow be determined using a topographic map? River Flow Direction: 3. Rivers always flow in the opposite direction from which contour lines bend when they cross the river. Example: Which direction is the Hammer Stream flowing? Hammer stream flows southeast
Review River Flow: Base your answers to questions 1 and 2 on the topographic map below.
12) What do features on a topographic map look like in real life? Profile: shows the side view of an Earth surface
12) What do features on a topographic map look like in real life? Example: Construct a profile for the topographic map below.
0 20 40 60 80 100 0 60 4020 80 100 0 A 20 40 60 80 100 0 B 60 40 20 80 100 Hilltop has to curve above the 100 m line, but does not hit the 120 line. 0 A 20 40 60 80 100 K. Coder 2015 0 B 60 40 20 80 100