Free Executive Summary - Elmhurst College

More documents

Recommendations

Info

$Math 346 Exam 2 Show all work in a neat and organized fashion ...$

Learning to Think Spatially: GIS as a Support System in the K-12 Curriculum http://www.nap.edu/catalog/11019.html SPATIAL THINKING IN EVERYDAY LIFE, AT WORK, AND IN SCIENCE 83 properties, or processes. The next step involves mentally manipulating those shapes, structures, orientations or positions—for example, by rotation, translation, deformation, or partial removal. The third step involves making interpretations about what caused the objects, properties, or processes to have those particular shapes, structures, orientations, and/or positions. With this understanding in mind, it is possible to make predictions about the consequences or implications of the observed shapes, internal structures, orientations, and/or positions. Finally, geoscientists can use spatial thinking processes as a short-cut, metaphor, or mental crutch to think about processes or properties that are distributed across some dimension other than physical space. 3.7 THINKING SPATIALLY IN GEOSCIENCE: THE SEAFLOOR MAPS OF MARIE THARP 3.7.1 Introduction: Seafloor Mapping Marie Tharp (1920–) is a marine cartographer who made some of the first maps of the seafloor between the 1950s and the 1970s (Figure 3.28). With kilometers of water obscuring her direct vision, she was able to visualize and depict the shapes of terrain that no human eye had ever seen. FIGURE 3.28 Marie Tharp at her worktable at Lamont Geological Observatory in Palisades, New York, 1961. She is seen with the Physiographic Diagram of the North Atlantic (1956), her six famous profiles of the Mid-Atlantic Ridge and Rift Valley, the “Physiographic Globe” by Dr. Bruce C. Heezen, and samples of PDR soundings. SOURCE: Photo taken by Nick Lazarnick. Copyright © National Academy of Sciences. All rights reserved.
Learning to Think Spatially: GIS as a Support System in the K-12 Curriculum http://www.nap.edu/catalog/11019.html 84 LEARNING TO THINK SPATIALLY Her maps have stood the test of time amazingly well when compared against modern maps made with sophisticated swath-mapping and satellite-based mapping systems. She created the maps using sparse and flawed echograms based on echo sounder data and her remarkable capacity for spatial thinking. Tharp’s decades-long effort involved synthesizing vast amounts of spatial data, visualizing what was previously unseen, and interpreting spatial observations in terms of causal processes. Marie Tharp worked at the Lamont-Doherty Earth Observatory of Columbia University in the research group of Professor Bruce Heezen. Earlier accounts (e.g., Menard, 1986) tended to give all or most of the intellectual credit to Heezen, recognizing Tharp only as the person who plotted the echograms. More recently, however, Tharp has been given credit for discovering the mid-Atlantic rift valley, correlating the rift valley and earthquake locations, and insisting on the validity of this as evidence for seafloor spreading at a time and place when this was considered to be heresy (Lamont- Doherty Earth Observatory, 2001). 3.7.2 The Nature of What Tharp and Heezen Did Measure Water Depths from Precision Data Recorders (PDRs). Echo sounders measure the depth of the water beneath a ship by measuring the travel time of an electronic ping of sound as it travels from the ship to the seafloor and back. In Tharp’s era, the state of the art was the precision depth recorder, as refined by the U.S. Navy during World War II. The echoes from the seafloor were recorded as burn marks on a roll of paper by a stylus that swept across the paper once per second. Tharp and her assistants manually converted the location of these burn marks into water depths, measuring a water depth for each 5 minutes of time along the track of a ship’s travel. Reconcile and Plot Navigation. Ship’s tracks were plotted by hand on table-sized plotting sheets at a scale of 4 inches to a degree of longitude, based on celestial navigation and dead reckoning by the ship’s officers. (On a modern research vessel, a navigation fix would be taken from the GPS every minute, the navigation would be logged by computer, and the ship’s track would be plotted automatically in real time.) Plot Soundings on Navigation Plots. Water depths were written by hand onto plotting sheets, alongside the ship’s track. Make Profiles and Contour Maps. Contours were drawn by hand on overlays of the plotting sheets. Profiles were made along azimuths that seemed interesting, sometimes combining segments of several different ship tracks to make a composite track (Figure 3.29). At this point we can begin to appreciate Tharp’s skill as a spatial thinker. Profiles and contour maps require judgments as to what is or is not interesting—which tracks to include or to discount. Plot Complementary Data at the Same Scale. Earthquake epicenter location and sediment data were plotted, by hand, at the same scale as the bathymetric data. This strategy revealed that earthquakes and thin sediment cover occurred along the axis of the mid-Atlantic ridge. Convert Profiles and Contours into Physiographic Diagrams. Heezen and Tharp’s most famous products are physiographic diagrams, scaled drawings or paintings of the seafloor as though all of the water had been drained away. Given the large gaps between track lines (tens to hundreds of kilometers even in the best covered areas; see Figure 3.30), creating a continuous physiographic diagram required substantial interpolation. Tharp gained a feel for the fabric or texture of the seafloor in areas of more abundant data and then used that “feel” to guide her mapping in the areas of less abundant data. We should note that this feeling was spatial or visual and intuitive, rather than being grounded in an understanding of the processes that formed the seafloor features because noone understood those processes during the early years of Tharp’s mapping career. The decision to use physiographic diagrams was initially motivated by the U.S. Navy’s classification and hence restriction of use of quantitative bathymetric data such as contours (Lawrence, Copyright © National Academy of Sciences. All rights reserved.
Page 1 and 2: http://www.nap.edu/catalog/11019.ht
Page 3 and 4: Learning to Think Spatially: GIS as
Page 35: Learning to Think Spatially: GIS as

Free Executive Summary - Elmhurst College

You also want an ePaper? Increase the reach of your titles

Delete template?

Save as template?