Topographic Maps Lab GE F23

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Iowa State University *

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100L

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Geography

Date

Jan 9, 2024

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pdf

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9

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Name: ______________________________________ Topographic Maps Lab Learning Goals ▪ Practice spatial thinking skills by translating information between 3-dimensional and 2- dimensional representations of the Earth’s surface. ▪ Develop an understanding of how a 2-dimensional topographic map represents the 3- dimensional surface of the Earth. Introduction: Earth processes and the results of these processes occur in three dimensional (3D) space, but we often represent such information in two dimensions (2D) using maps. An important skill for scientists, therefore, is the ability to translate information back and forth between 2D and 3D. Topographic maps, or elevation maps, are a common way to represent Earth’s 3D surface in an information -dense 2D format. Part 1: Interpreting topographic maps (2D → 3D) The first part of this lab will involve learning how topographic features, such as mountains, ridges, and stream drainages, are represented on topographic maps. You will be asked to translate from a 2D map to a 3D surface that you sculpt in an Augmented Reality Sandbox (ARS). Only one team of 2-3 students can use the ARS at a time. Please spend no more than 15 minutes with the ARS to ensure that all teams have time to work with it. Part 2: Interpreting 3D terrains (3D → 2 D) Students will use digital landscapes in Google Earth to identify ridges and valleys and plan a hypothetical hike through the badlands of northern Wyoming.
Glossary and “Rules of Thumb” for Topographic Maps A contour line connects points of equal elevation on a topographic map. Contour lines always separate points of higher elevation from points of lower elevation. For example, the 100 contour line separates the 104 point from the 96 point on the map to the right. One can determine which way is uphill or downhill on the map by checking adjacent areas with labeled contour lines. The contour interval is difference in elevation between any two contour lines. On the map to the right, the contour interval is 10 units. Some contour maps show heavier contour lines that are labeled with an elevation separated by finer contour lines that are not labeled. These lines are called index contours and minor contour lines, respectively. The closer the contour lines are on a map, the steeper the slope or gradient. In other words, steep slopes are represented by closely spaced contour lines. If the spacing between contour lines changes on a slope, then the steepness of the slope has changed. Contour lines never cross each other, but they may merge to represent vertical surfaces, like cliffs or walls. Valleys, and streams are represented on topographic maps with a V pattern in which the apex, or point, of the V points uphill. Closed, concentric rings of contour lines represent a hill or peak of a mountain. Closed, concentric rings of contour lines with hachure marks represent closed depression or pits.
Part 1: Interpreting topographic maps (2D → 3 D) Each group must choose either the Mount St. Helens topographic map or the Island of Hawaii topographic map and complete the associated exercise and questions. Map 1: Mount St. Helens Elevation shown in meters. N
Recreate the Mount St. Helens topographic map using the Augmented Reality Sandbox (ARS) and answer the following questions. Contour lines shown by the ARS do not need to perfectly match the contour lines shown on the map. Once you have finished: • U se the keyboard command “Function+PrtScn” to save a screen capture to the desktop; and • Please include your section number and last names of your group members in the file name. Question 1: What is the highest elevation shown on the Mount St. Helens topographic map? Be sure to include units. Question 2: What is the lowest elevation shown on the Mount St. Helens topographic map? Be sure to include units. Question 3: What is the contour interval of the Mount St. Helens topographic map? Be sure to include units. Question 4: Locate three (3) valleys on the Mount St. Helens topographic map. Label the valleys on the map by drawing a stream (dashed or solid line) running through each valley and label the line “stream.” What features on the topographic map did you use to locate the valleys? Question 5: In 1980, an earthquake within Mount St. Helens caused a side of the volcano to collapse, triggering an explosive eruption that sent a pyroclastic flow down into the surrounding area. Which side of Mount St. Helens collapsed due to the earthquake? Explain your reasoning by describing the shape of your ARS model. Question 6: Seconds after the first blast, an enormous vertical eruption occurred at Mount St. Helens which blew the top off of the mountain creating a nearly circular depression or caldera. Which has a steeper slope? The inside of the caldera or the flank of the volcano? Explain your reasoning.
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