Maps as models of the earth/Contour models Topic

Maps as models of the earth/Contour models

Science, Grade 6

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Study Guide Maps as models of the earth/Contour models Science, Grade 6

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MAPS AS MODELS OF THE EARTH Overview Geologists use a variety of different types of maps to model or depict the three-dimensional Earth on a two-dimensional surface. Each type of map serves a purpose because each type has its special strengths. All maps, however, also have their weaknesses, so geologists use the map that is best for the application at hand. Topography and Topographic Maps Topographic maps use contour lines to show elevation and the contours (that is, the changes in elevation) of the land. Very close contour lines indicate the elevation is changing rapidly and is, therefore, very steep. Widely spaced contour lines, on the other hand, indicate less dramatic changes in elevation. Contours create specific shapes when they intersect various land features. For example, contours always form a V-shape that points upstream when they intersect rivers and streams. Contours form concentric circles when they indicate individual hills (or depressions). © Copyright NewPath Learning. All Rights Reserved. Permission is granted for the purchaser to print copies for non-commercial educational purposes only. Visit us at www.NewPathLearning.com.

For a topographic map to be fully useful, one must know the difference in elevation between two consecutive contour lines. This is called the contour interval. The larger the contour interval, the more dramatic the changes in elevation between contour lines. Smaller contour intervals indicate gently rolling topography and relatively small changes in elevation from one point to another. Lesson Checkpoint: How are landforms displayed on maps? Other Types of Maps Topographic maps show the three-dimensional differences in elevation in a particular region. Earth scientists need a variety of other types of maps to be able to effectively study the Earth. Some of these other types of maps include Mercator Projections, Conic Projections, and Azimuthal Projections. As the surface of the Earth is projected onto the two-dimensional surface, different portions of the map are distorted while others remain more accurate. • Mercator Projections are maps created by projecting the surface features of the Earth onto a cylinder of paper. © Copyright NewPath Learning. All Rights Reserved. Permission is granted for the purchaser to print copies for non-commercial educational purposes only. Visit us at www.NewPathLearning.com.

• Conic Projections are created when the surface of the Earth is projected onto a piece of paper folded into a cone shape. Conic Projection Map • Azimuthal Projections are created by projecting a portion of the Earth’s surface onto a flat piece of paper; the paper touches the globe at a single point (usually the North or South Pole.) By comparison, Azimuthal Projections are very accurate near the point of contact but become more distorted further away from the point of contact. Azimuth Projection © Copyright NewPath Learning. All Rights Reserved. Permission is granted for the purchaser to print copies for non-commercial educational purposes only. Visit us at www.NewPathLearning.com.

Symbols Tell the Story In order for any type of map to be of value, one must understand the symbols and purposes of the different maps. Every map has a scale to indicate the relationship between distance on the map and distance on the Earth’s surface. Maps have a compass rose to indicate North, South, East and West on the map. Maps must have a legend indicating the meanings of the various symbols used on that particular map. The symbols on different maps can vary widely from each other; the symbols used will be very much dependent on the purpose of the particular map. Also, a date the map was created and a title for the mapped region is included in the legend. Lesson Checkpoint: Where do you look on a map to find out which direction points North? © Copyright NewPath Learning. All Rights Reserved. Permission is granted for the purchaser to print copies for non-commercial educational purposes only. Visit us at www.NewPathLearning.com.

International Conventions Help Share Knowledge There are basic conventions that all scientists and cultures agree to in order to make maps useful worldwide. Defining the location of any specific town, city, or location on the Earth is done using degrees of longitude and latitude. By international agreement, imaginary lines that pass through the poles are called meridians or lines of longitude. In addition, the beginning meridian would be considered 0 degrees and would be called the Prime Meridian. Distances are measured in degrees, East and West, of the Prime Meridian. The Prime Meridian runs through the poles and through Greenwich, England. It is also agreed that the imaginary lines that measure distance and direction from the Equator north and south to the poles are called lines of latitude (also called parallels because they are parallel to one another). The equator is 0 degrees latitude. The equator is the line that is exactly halfway between the North and South poles. Latitude is measured by degrees North and degrees South of the equator. By using these conventions, it is possible to locate any specific point on the Earth and define it in terms of degrees longitude and latitude. Lesson Checkpoint: Name one universal convention of measurement on a globe which is used to make maps useful throughout the world? © Copyright NewPath Learning. All Rights Reserved. Permission is granted for the purchaser to print copies for non-commercial educational purposes only. Visit us at www.NewPathLearning.com.