MAPS: CONTOURS, PROFILES, AND GRADIENT PDF

12/2/24, 10:45 AM MAPS: CONTOURS, PROFILES, AND GRADIENT MAPS: CONTOURS, PROFILES, AND GRADIENT - Pages 45 through 58 in your lab manual Authors: David Leveson and...

12/2/24, 10:45 AM MAPS: CONTOURS, PROFILES, AND GRADIENT MAPS: CONTOURS, PROFILES, AND GRADIENT - Pages 45 through 58 in your lab manual Authors: David Leveson and C.E. Nehru Edited for the web: Guillermo Rocha Materials needed to complete this lab: ruler, string, and a calculator. https://academic.brooklyn.cuny.edu/geology/grocha/mapcontour/ 1/30 12/2/24, 10:45 AM MAPS: CONTOURS, PROFILES, AND GRADIENT Elevation - The Earth’s surface is highly irregular, displaying mountains, valleys, cliffs, slopes and depressions. Topographic maps employ contours as the best way of efficiently and accurately representing the three-dimensional character of the Earth’s surface on a flat, two-dimensional surface. A contour is a line on a map that connects adjacent points of equal elevation. https://academic.brooklyn.cuny.edu/geology/grocha/mapcontour/ 2/30 12/2/24, 10:45 AM MAPS: CONTOURS, PROFILES, AND GRADIENT CONTOUR INTERVAL (C.I.) - A contour interval is the vertical distance or difference in elevation between contour lines. If the numbers associated with specific contour lines are increasing, the elevation of the terrain is also increasing. https://academic.brooklyn.cuny.edu/geology/grocha/mapcontour/ 3/30 12/2/24, 10:45 AM MAPS: CONTOURS, PROFILES, AND GRADIENT CLOSED CONTOURS - Represent hills or mountains. The inner most closed contour has the highest elevation; the outermost closed contour has the lowest elevation HACHURED LINES - Represent depressions, volcanic craters, and basins. The innermost hachured contour has the lowest elevation; the outermost hachured contour has the highest elevation. https://academic.brooklyn.cuny.edu/geology/grocha/mapcontour/ 4/30 12/2/24, 10:45 AM MAPS: CONTOURS, PROFILES, AND GRADIENT RULE OF "Vs" - Contour lines form a "V" when they cross a stream or river. The point of the V points uphill; the legs of the "V" point downhill. https://academic.brooklyn.cuny.edu/geology/grocha/mapcontour/ 5/30 12/2/24, 10:45 AM MAPS: CONTOURS, PROFILES, AND GRADIENT A hachured contour line, lying between two different contour lines, is the same elevation as the lower contour line. A closed contour line, lying between two different contour lines, is at a higher elevation than the lower contour line. Contour lines close together = steep slope Contour lines far apart = gentle slope https://academic.brooklyn.cuny.edu/geology/grocha/mapcontour/ 6/30 12/2/24, 10:45 AM MAPS: CONTOURS, PROFILES, AND GRADIENT https://academic.brooklyn.cuny.edu/geology/grocha/mapcontour/ 7/30 12/2/24, 10:45 AM MAPS: CONTOURS, PROFILES, AND GRADIENT Profile - A topographic profile is a cross-sectional view along a line drawn through a portion of a topographic map. One can think of a profile as a slice through a portion of the terrain (as you were slicing a cake and looking at the vertical face the slice). https://academic.brooklyn.cuny.edu/geology/grocha/mapcontour/ 8/30 12/2/24, 10:45 AM MAPS: CONTOURS, PROFILES, AND GRADIENT https://academic.brooklyn.cuny.edu/geology/grocha/mapcontour/ 9/30 12/2/24, 10:45 AM MAPS: CONTOURS, PROFILES, AND GRADIENT Vertical Exaggeration - Vertical exaggeration is computed by dividing the horizontal scale of the map by the vertical scale of the profile. Both scales https://academic.brooklyn.cuny.edu/geology/grocha/mapcontour/ 10/30 12/2/24, 10:45 AM MAPS: CONTOURS, PROFILES, AND GRADIENT should be converted to the same units before dividing. Gradient - Topographic maps are not just used for determining elevation, they can also be used to help visualize topography.One of the most basic topographic observation that can be made is the gradient (or slope) of the ground surface. High (or steep) gradients occur in areas where there is a large change in elevation over a short distance. Low (or gentle) gradients occur where there is little change in elevation over the same distance. Gradient is simply the rise over the run or the slope (change in y (elevation) divided by the change in x (distance)). Gradient is equal to the elevation change divided by the horizontal distance. https://academic.brooklyn.cuny.edu/geology/grocha/mapcontour/ 11/30 12/2/24, 10:45 AM MAPS: CONTOURS, PROFILES, AND GRADIENT Since most rivers are curvilinear, we cannot use the ruler directly to measure their lenghts. Instead we have to take an additional step, that is we have to use a string and carefully lay the string along the curved lines that the river makes. Once we got that lenght on the string, then we go and measure that lenght against the ruler. Only then, we will have measured the true lenght along the bending lines of the river. https://academic.brooklyn.cuny.edu/geology/grocha/mapcontour/ 12/30 12/2/24, 10:45 AM MAPS: CONTOURS, PROFILES, AND GRADIENT Relief - An important property of a landscape is its relief: the difference in elevation between the highest point and the lowest point https://academic.brooklyn.cuny.edu/geology/grocha/mapcontour/ 13/30 12/2/24, 10:45 AM MAPS: CONTOURS, PROFILES, AND GRADIENT https://academic.brooklyn.cuny.edu/geology/grocha/mapcontour/ 14/30 12/2/24, 10:45 AM MAPS: CONTOURS, PROFILES, AND GRADIENT Examples 1 and 2 What is the value of Y? Example 1 - First we see the labeled contour at 750 feet and by the close contours we know we are going up towards Y at increments of 5 feet, given by the contour interval (C.I. =5'). Label the contours based on that information (values on red).From there we can see that Y is greater than 760 feet and less than the upcoming contour (not on the map) 765 feet. Y>760' and Y850' and Y300' and Y120' and Y