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Map Distortion

The content and activities in this topic will work towards building an understanding of how maps distort continents and ocean basins.

Map Types

Two types of maps commonly used to show the surface areas of the ocean basins and continents are equal-area maps and cylindrical-projection maps (see Figs. 1.6 and 1.7). In Figs. 1.7 and 1.8, a grid is superimposed on the map. At the equator of each map one square represents a surface area of about 1,240,000 square kilometers (or 1.24 X 106 km2).  
 
<p><strong>Fig. 1.6. </strong>Equal-area map with superimposed grid. One square at the equator represents a surface area of about 1,240,000 square kilometers. On this map land is green even if it is covered by ice. This map does not show sea ice.</p><br />
<p><strong>Fig. 1.7.</strong> Cylindrical-projection map with superimposed grid. One square at the equator represents a surface area of about 1,240,000 square kilometers. On this map land is green even if it is covered by ice. This map does not show sea ice.</p><br />

<p><strong>Fig. 1.8</strong> (<strong>A</strong>) equal-area map creation</p><br />
<p><strong>Fig. 1.8</strong> (<strong>B</strong>) cylindrical projection map creation</p><br />

An equal-area map is created by treating the earth like an orange. To get the orange peel to lay flat, it is necessary to make a lot of cuts (Fig. 1.8 A). To make a cylindrical-projection map, think of the earth as a clear globe with black outlines of its features lit from within. To make a flat map, the globe is wrapped in a paper cylinder and the projections of the outlines are traced (Fig. 1.8 B).

Activity

Activity: How Much Water?

Using two maps of the world, determine approximately how much of the surface of the earth is land and how much is covered by water.

 

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Exploring Our Fluid Earth, a product of the Curriculum Research & Development Group (CRDG), College of Education. University of Hawaii, 2011. This document may be freely reproduced and distributed for non-profit educational purposes.