Unit 7 Lesson 4 : Topographic Maps

Transcription

1 Unit 7 Lesson 4 : Topographic Maps Edit File Screen 1 - W elcom e PRI OR KNOWLEDGE W hy do people use m aps? People use m aps to see where they are and to find out how to get where they want to go. For w hat places are there m aps? There are m aps for cities, states, countries, and the world. There are also m aps for am usem ent parks, neighborhoods, and m alls. W hat's the purpose of a m ap? The purpose of a m ap is to show your position relative to other locations. Screen 2 - Essential question PREREQUI SI TE KNOWLEDGE W hat does the suffix "- graph" m ean? The suffix "-graph" m eans written or drawn. Maps are drawn. PRI OR KNOWLEDGE W hat does "cont our" m ean? A contour is an outline of som ething. LEARNI NG STRATEGI ES (ELL) W hat does the w ord "scale" m ean outside of t he classroom? The word "scale" has m any m eanings. A fish has scales on its skin, or you can weigh yourself on a scale. Screen 3 - The Grand Canyon ENGAGE W hy m ight you need a m ap at the Grand Canyon? The Grand Canyon covers a lot of area. Without a m ap, you could get lost. W hat do you think the m ost difficult part about hiking in the Grand Canyon is? Hiking up from the bottom would be the hardest part, because of the steep incline.

2 W hat supplies m ight you need to t ake w ith you on a hike t hrough the Grand Canyon? First and forem ost, you need to take water to drink. Then, you m ay want to take a jacket in case it cools off. Assum ing your hike will take m ost of the day, you should take food. DEVELOP SCI ENCE VOCABULARY W hat's an elevation? On m aps, elevation refers to an object or landform 's height above sea level. Screen 4 - Maps are m odels W hy are m aps useful to scientists? Maps are m odels of Earth. They com m unicate inform ation about very large areas in a sim ple and clear way. W hy are scientists interested in landform s? Scientists can learn a great deal about landform s. They can learn how Earth changes over tim e. They can study how hum an activity affects the land and water. And they can learn to predict things such as earthquakes and volcanic eruptions. LEARNI NG ALERTS Do new political m aps ever need to be m ade? Political m aps change often. For exam ple, in 1991 the Soviet Republic becam e a group of independent states. All of the m aps that showed the Soviet Republic were out of date, so new m aps had to be m ade. Screen 5 - Parts of a m ap W hat does a com pass rose show you? A com pass rose shows you which direction is north, south, east, and west. As long as one direction is given, the others can be determ ined. Usually, if only one is given, it's north. A legend tells w hat the features on a m ap m ean. W hat does the color blue often represent? Blue usually represents water.

3 The scale on a m ap reads 3 centim eters: 8 0 kilom eters. I f the distance you'll travel on a m ap is 1 0 centim eters, about how far w ill you go? You'll go about 267 kilom eters. Screen 6 - Types of m aps W hat's the purpose of a geologic m ap? A geologic m ap has a specialized purpose, which is to show the geologic properties of the land. That includes the types of rocks and how old they are as well as folds and faults. I n term s of how t hey show elevation, how are physical and topographic m aps different? Topographic m aps use lines to show elevation while physical m aps use color. W hy are political m aps of little interest to earth scientists? Political m aps indicate political lines that are established by hum ans. These lines are arbitrary and can change at any tim e. Com pare m aps from 1985 and Many boundary lines have changed. Screen 7 - I m ages from the air DEMs are sim ply files w it h data that are used to generate m aps. W hat inform ation do you t hink is found in DEM files? The inform ation in the files is the elevation of certain points on Earth's surface. How are aerial satellite im ages sim ilar? Aerial and satellite im ages can both capture im ages of Earth and zoom in to view specific details. PRI OR KNOWLEDGE W hat causes Earth's surface to change? Earthquakes, volcanoes, and landslides all cause changes to Earth's surface.

4 Screen 8 - Parts of topographic m aps How are political and topographic m aps alike? They both can show hum an-m ade features. LEARNI NG ALERTS How can you tell w hat features are represented by lines on a topographic m ap? The color, size, and pattern of the line will indicate what feature is being represented. W hat's an area sym bol? An area sym bol is a closed shape that represents a larger feature, like a lake or park. Screen 9 - Use of im agery PROBI NG QUESTI ON Aerial and satellit e im ages and data are used w ith com puters to update and generate m aps. Before this kind of technology existed, how do you t hink m aps w ere m ade? How did m apm akers know elevations and distances as they collected data to m ake their m aps? Mapm akers can gather data in the field, by walking along an area and m aking stops to m easure distance, elevation, and by noting features. To know their bearing, they use a com pass. To know the distance between stops, m apm akers can count paces. To know the elevation change between two stops, scientists could m easure the average slope between the stops. Knowing the distance and slope allows them to find the elevation change. Now, m apm akers can use GPS devices as they do field m apping, which autom atically tell your elevation and position. How can a GPS track w here you are as you travel? Satellites send data to the GPS that allows it to track the exact location and velocity. W hat value do old m aps have, even after they've been updated and replaced? Old m aps are a historic record of a specific tim e. They can be used for com parison with new m aps to see changes in Earth's surface.

5 Screen High and low relief DI FFI CULT CONCEPTS Does an area of low relief also have a low elevation? Not necessarily. An area that has low relief doesn't change m uch in elevation; it's relatively flat. There are flat areas at high elevations, such as plateaus. How can you determ ine the topography of the land using contour lines? Because contour lines show changes in elevation, you can track whether the land goes up or down from a location and how quickly it changes. The pattern in the changes of elevation tell you what the topography of the land is. W hy are the contour lines close together in an area of high relief? High relief m eans there's a large change in elevation, which m eans an area is steep. On a m ap, there's a change in elevation between one contour line and the next. The am ount of change is constant; for exam ple, a m ap m ight show an elevation change of 20 feet between each contour line. The closer together the lines are, the steeper the land is. Screen Contour intervals SYNTHESI S Tw o m aps have sim ilar areas. The cont our lines have the sam e spacing, but the land they represent is very different. One of them has a steep m ountain, and the other is a gradual hill. How w ill the m aps be different? The part of the m ap that's different is the contour interval. While the hill's m ap m ay have a contour interval of 10 feet, the steep m ountain's m ay be 100 feet. W hy isn't every contour line labeled? The m ap would be too cluttered, m aking it difficult to read. I ndex contours and contour intervals m ake it possible to calculate the elevation of every contour line. W hy aren't contour lines straight? Contour lines could be straight, although they're usually curved. They follow the elevation of the land, which tends to create curves.

6 Screen Contours and relief You're looking at a m ap w here the elevation is only labeled on each, bold, index contour. Explain, step by step, how to find the elevation change, or contour interval, betw een each contour line. Step 1: Find the elevation difference between two index contours. Step 2: Count the num ber of spaces between the index contour lines. Step 3: Divide the difference in elevation between the two index contours by the num ber of spaces between the index contour lines. LEARNI NG STRATEGI ES (ELL) W hat does "relief" m ean? "Relief" m eans to ease a burden or stress. For a topographic m ap, relief is the difference in the highest and lowest elevations of an area. DEVELOP SCI ENCE VOCABULARY W hat's an interval? An interval could be a space in, or a break between, two things. I t could be a break in tim e as well. On a topographic m ap, the contour interval is the space between two contour lines; specifically, it's the elevation change between one contour line and the next. Screen Contour lines W hen there's an overhanging cliff, contour lines m erge. Can you explain w hy? There's land at two elevations in one spot on Earth's surface. W ould you expect the contour lines on a m ap of a desert to be spaced close together or far apart? I t would depend on the desert. Traditionally, deserts are thought to be flat expanses of land where the contour lines would be spaced far apart. However, there are m ountainous regions in deserts, too, so the contour lines could be close together. How can you tell the difference betw een a hilltop and a depression? A depression contour has lines inside the closed loop pointing to the lowest point.

7 Screen Mapping land features WHY I T MATTERS W hat are som e other exam ples of people w ho w ould use a topographic m ap? Anyone who's involved with geographic planning and architecture, m ining projects, or outdoor activities like cam ping and fishing m ight find a topographic m ap useful. How do you calculate the slope of the land? Choose two points. Divide the change in vertical distance by the change in horizontal distance. That's the slope. How can you tell if t he slope is decreasing for t he land? The contour lines will becom e farther apart. The change in elevation from the bottom to the top of a hill is 1 0 m. The distance from the top to the bottom is 2 0 m. Find t he slope of t he hill. Divide 10 m by 20 m to get 0.5. Because slope is often expressed as a percentage, m ultiply by 100 to obtain the percent slope, which is 50 percent. Screen Gentle slope LEARNI NG ALERTS W hat do contour lines look like at a m ountain peak? As the lines go up toward the m ountain peak, they becom e closed concentric loops that get sm aller and sm aller. PROBI NG QUESTI ON A topographic m ap show s an area of high relief w it h cont our lines that are very close together on one side and very far apart on the other. W hat m ight that suggest about the area's geology? This m ight be showing a steep cliff, a road-cut along a hill, or a faulted m ountain. A topographic m ap show s a flat, round area w here the contour lines are spaced very far apart. On the edges of t his area, the contour lines suddenly becom e very closely spaced together and go dow n for a w hile. Then, the land

8 suddenly flattens out again. W hat feature is represented? A plateau with edges that get steeper as you approach the m esa. Screen Land features on the m ap W hich m ap w ill show greater detail: a m ap w ith a contour level of 2,0 0 0 feet or one w ith a contour level of feet? W hy? The m ap with a contour level of 500 feet will show greater detail because there will be m ore contour lines. W hat are som e features that are represented by points on a topographic m ap? Points could represent houses, buildings, cam psites, springs, water sources, or m ines. W hat are som e features that are represented by lines on a topographic m ap? Lines could represent stream s, rivers, ditches, roads, or railroads. W hat can't be m easured using contour lines: the height of m ountains, the depth of the ocean floor, t he distance around a plateau, or the steepness of slopes? The distance around a plateau can't be m easured using contour lines. Screen Topography Contour lines are usually sm ooth, but can be straight or j agged. W hen m ight they not be sm ooth? Contour lines m ight not be sm ooth along fractures in Earth s surface or along road cuts. How are bathym etric m aps like topographic m aps? How are they different? They both use contour lines to show the elevation of Earth's surface. Bathym etric m aps describe the surface under the ocean. WHY I T MATTERS How could a topographic m ap help a biker plan a route for a ride? A topographic m ap can help a biker choose the kind of terrain desired for the ride. I t will tell the biker if there are flat areas or steep hills on a certain path.

9 Screen Essential question review W hat do you t hink is m eant by t he term "m ap relief"? Oftentim es, a person talks about the relief of a m ap, which is the difference between the highest and lowest points on the m ap. WHY I T MATTERS How could a topographic m ap be useful w hen planning w here to place a building? A topographic m ap could show where there's a flat area. I t could alert you to potential dangers such as a hillside or slope that could have a landslide.