How are elevation and topography shown on a map? What are three types of information shown in geologic maps? What are two uses of soil maps?

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1 CHAPTER 3 3 Types of Maps SECTION Models of the Earth KEY IDEAS As you read this section, keep these questions in mind: How are elevation and topography shown on a map? What are three types of information shown in geologic maps? What are two uses of soil maps? What Is a Topographic Map? There are many different kinds of maps. Each kind of map shows different information. One common kind of map is a topographic map. A topographic map is a map that shows the surface features, or topography, of an area. Topographic maps show three main things: natural features, such as rivers and lakes features made by people, such as bridges elevation, or the height of an object above sea level Look at the two figures below. The figure on the left shows a picture of an island. The figure on the right shows a topographic map of the same island. READING TOOLBOX Ask Questions Read this section silently. As you read, write down questions that you have about this section. Discuss your questions in a small group. X Apply Concepts About how long is this island from the southwest corner to the northeast corner? 1 km The topographic map on the right shows the features and elevation of the picture on the left. An X marks the highest point on the map. The picture of the island shows the island s shape. A regular map of the island could use a scale to show its size. The topographic map shows the island s topography, in addition to its shape and size. In this way, a topographic map gives more detail than a picture or a regular map. 2. Compare How is a topographic map different from a regular map? Holt McDougal Earth Science 39 Models of the Earth

2 Type of Model What It Shows Shape Size Elevation Picture X Regular map X X Topographic map X X X Critical Thinking 3. Infer Why is a contour line a type of isogram? CONTOUR LINES Topographic maps use contour lines to show elevation. A contour line is an isogram that connects points with the same elevation. Contour lines that are far apart show a gradual change in elevation. Contour lines that are close to each other show a steeper slope. 4. Identify Circle an area on the map that has a steep slope. Put a square around an area that has a gentle slope. contour interval = 10 m The distance between contour lines shows how steep or gentle a slope is. Critical Thinking 5. Apply Concepts A point on a map is halfway between the contour line and the 60 m contour line. What is the elevation of the point? A contour interval is the difference in elevation between two contour lines. For example, the map above has a contour interval of 10 m. Therefore, the difference in elevation between two contour lines is 10 m. Some contour lines are drawn darker than others. These darker lines are called index contours. They make the map easier to read. In the map above, every fifth contour line is an index contour. You can estimate the elevation of a point on a map by looking at the two contour lines near it. The elevation of that point is between the elevations of the two contour lines. For example, a point halfway between the 100 m and 110 m contour lines has an elevation of about 105 m. Some points on a topographic map are marked with an. A number is written next to the. That number is the exact elevation of that point. Holt McDougal Earth Science 40 Models of the Earth

3 RELIEF ON TOPOGRAPHIC MAPS Relief is the difference between the highest elevation and the lowest elevation on a topographic map. On some maps, the relief can be as large as 100 m. On other maps, it may be as small as 1 m. OTHER SYMBOLS ON TOPOGRAPHIC MAPS Most topographic maps use colors and symbols to represent objects. For example, a map might have symbols to show roads, railroads, and buildings. These symbols are generally black. Bodies of water are generally blue, and forests are generally green. Major highways are red. The shapes of contour lines can give you information about the landforms on a map. For example, a contour line may be shaped like a small, closed circle. That contour line represents either a hill or a very low area. A contour line shaped like a V represents a valley. If there is a river in the valley, the V will point upstream. It points in the direction opposite that of the river s flow. 6. Identify What color is generally used to show water on a topographic map? Closed circle: top of a hill V-shaped Contour Line 100 m contour interval = 10 m 7. Apply Concepts What is the elevation of the top of the mountain in the top right corner of the map? The shapes of contour lines give information about landforms. What Is a Soil Map? Earth scientists use soil maps to show the properties of the soil in an area. People can use soil maps to understand how to use land most efficiently. They can also use the maps to identify ways to conserve soil. Holt McDougal Earth Science 41 Models of the Earth

4 SOIL SURVEYS To create a soil map, cartographers do a soil survey of the area. During the soil survey, they record information about the types of soils in the area. They collect samples of soil from many different places in the area. The figure below shows an example of a soil map. Soil maps help scientists understand how to best use the land in an area. Talk About It Investigate Use the Internet or library to find a soil map for your county or for another area. Find out which areas on the map are best for growing different kinds of plants, such as corn, wheat, or pine trees. Share what you learn with a partner or a small group. 8. Describe How do geologic maps show different geologic units? What Are Geologic Maps? Geologic maps show the geologic features of Earth. Most geologic maps show the types of rocks in an area. They also show the locations of geologic structures. Most geologic maps start with a base map. The base map shows features such as mountains or roads. As Earth scientists study an area, they learn about the different kinds of rocks and other landforms in the area. They mark that information on the base map. They add color and special symbols to represent different landforms. Cartographers use different colors to represent the geologic units on a geologic map. A geologic unit is a layer of rock that is all the same age and type. Units that are similar ages generally have similar colors. Cartographers label each geologic unit with a set of letters. The set contains one capital letter and one or more lowercase letters. The capital letter stands for the rock s age. The lowercase letters stand for the type of rock. Holt McDougal Earth Science 42 Models of the Earth

5 CONTACT LINES Geologic maps also contain symbols called contact lines. A contact line is a place where two geologic units meet. There are two main kinds of contact lines: depositional contacts and faults. Depositional contacts show where one rock layer formed above another. Faults are cracks where rocks move past each other. 9. Identify The geologic units on this map are separated by black lines. What are the black lines called? Each color on this map shows a different type and age of rock. Scientists can use this geologic map to see which types of rocks are in this area. What Are Some Other Types of Maps? Topographic maps, geologic maps, and soil maps are not the only kinds of maps Earth scientists use. Earth scientists may use maps to show the movements of wind and water. They may use maps to show where earthquakes and volcanoes are likely to happen. Different scientists use maps in different ways. For example, meteorologists use some maps to predict weather events. These maps may show the amount of precipitation that falls on different areas. They may also show the location of high and low atmospheric pressure. Meteorologists use these maps to predict weather and to warn people about weather emergencies. Some maps show where and how groundwater flows. Structures and systems such as power plants, garbage dumps, and new communities can pollute groundwater. Geologists can use groundwater maps to find the best places to build such structures. Other maps help geologists to study changes in Earth s surface over time. Geologists may use these maps to study changes in topography, in the amounts of available natural resources, and in climate. 10. Explain Why is it important for meteorologists to share the information on their maps with the public? Holt McDougal Earth Science 43 Models of the Earth

6 Section 3 Review SECTION VOCABULARY contour line a line that connects points of equal elevation on a map elevation the height of an object above sea level relief the difference between the highest and lowest elevations in a given area topography the size and shape of the land surface features of a region, including its relief 1. Explain A small topographic map contains the following contour lines (in meters): 40, 50, 60, 70, 80, 90. What is the relief of the map? What is the contour interval? 2. Infer How could a topographic map be useful for a hiker? 3. Apply Concepts An Earth scientist is studying the geologic history of an area. She wants to know when different rock layers in the area formed. Which kind of map should she use? Explain your answer. 4. Identify What are two ways people use soil maps? 5. Compare Complete the table below to compare topographic maps, geologic maps, and soil maps. Type of Map What Colors Represent on the Map What Lines Represent on the Map Topographic map black = roads and buildings; blue = water; green = forest; red = major highways different geologic units places where different kinds of soil touch 6. Identify Give two examples of how people can use maps to help the environment. Holt McDougal Earth Science 44 Models of the Earth

WHAT MAPS SHOW US Maps do 4 things:

WHAT MAPS SHOW US Maps do 4 things: WHAT MAPS SHOW US Maps show us a range of features, for example: Landforms: Settlement: Communication: Land Use: Geology: Other Info: - hills - valleys - mountains - isolated dwellings - farms - villages