Eileen Herrstrom

University of Illinois at Urbana-Champaign

Undergraduate class on introductory physical geology, geography or quantitative reasoning for non-majors

This activity does not have any prerequisites as it introduces topographic maps.

This is a laboratory activity preceding other assignments that use topographic maps and is the sixth laboratory exercise of the course.

Find pertinent information about a topographic quadrangle, determine elevations of points on and off contour lines, and calculate the relief and slope between pairs of points

Compute the relief and average slope along the line of a topographic profile, visualize how the landscape changes along the profile, and construct and interpret a topographic profile

Identify the horizontal scale of a topographic profile from the map scale, determine the fractional vertical scale of a profile from the verbal scale, and calculate the vertical exaggeration of several topographic profiles

Programs such as Google EarthTM and NASA World Wind provide satellite images of any point on the planet. These and other tools allow us to build models of the landscape, draw topographic profiles, measure straight-line distances and the length of winding streams, and estimate slope steepness. Why are geologists interested in maps? We use them as the fundamental tool for communicating information about the distribution of rock units and landforms. If you ever go to a national park, you will find topographic and geologic maps of the park area at the visitor center. In fact, you can even download an electronic version of the map showing your neighborhood from the US Geological Survey website.

Student materials for this exercise include the instruction sheet and a .zip file containing the topographic map (PDF and JPG versions of the full map plus a PDF for the topographic profile). The exercise is divided into three parts.

Part I introduces the concept of a topographic map and the basic information relevant to reading a map. Students determine elevations of points on and off contour lines, including spot elevations, and calculate relief and slope.

In Part II, students construct a topographic profile by hand and use it to interpret the landscape along the profile line.

Part III involves calculating the fractional horizontal and vertical scales of various profiles and using them to compute vertical exaggeration of examples and of the profile from Part II.

In both the traditional face-to-face and online versions of the course, this activity is assessed based on the answers to the questions. It is also possible to have students submit their completed profiles, although this option works best in a small class.

U.S. Geological Survey, 2005, Topographic map symbols: U.S. Geological Survey Unnumbered Series, GIP, 4 p.: Online resource – Accessed 16 June 2019
https://pubs.usgs.gov/gip/TopographicMapSymbols/topomapsymbols.pdf

TopoView, 2018, U.S. Geological Survey: Online resource – Accessed 16 June 2019
https://ngmdb.usgs.gov/topoview/viewer/#4/39.98/-99.93

McIntosh-Tolle, L., 2018, How to read a topo map: REI Coop: Online resource – Accessed 16 June 2019
https://www.rei.com/learn/expert-advice/topo-maps-how-to-use.html