Physical Geography

timer Asked: Apr 18th, 2017

Question Description

I need a complete answers on the geography questions. short answers needed

Please use the below instruction to answer all the questions Introduction – Section 1 Topography is the shape of the land. Topographic maps are used to aid in the visualization of the shape of the land. Topographic maps include the accurate representation of places, directions, distances and elevations. People use topographic maps for things like planning a hike and purchasing a piece of property. Elevation and Contour Lines: Elevation, typically measured relative to sea level whose elevation is arbitrarily said to be zero, is represented by contour lines on topographic maps. A contour line is a line of equal elevation. Contour lines are vertically spaced using contour intervals (CI). For instance, USGS topographic maps commonly space contour lines 5, 10, 20, 40, or 80 feet apart. Hence, using a 20-foot contour interval each contour line is represents a change in elevation of 20 feet relative to adjacent contour lines. Only one contour interval is used per map. The contour interval of a typical USGS topographic map is given beneath the graphical scale bar. Remember, contour lines never cross. When the contour interval is not specified, subtracting the value of two labeled contour lines and dividing by the number of contour lines between them can calculate the contour interval. In most cases, the labeled contours are bold lines that are called index contours. Index contours always have 5 contour lines between them. Contour intervals differ from map to map based on relief of the region (i.e., mountainous vs. flat plains). Some maps will be in feet, while others will have units of meters. Make sure to look closely at the map to see if it is using English units or the International System (SI) units. When determining the elevation of a point on a contour line, report it as the value of the contour line (e.g. 20 ft). When determining the elevation of a point between contour lines, interpolate the elevation to the closest foot. If this isn't possible, give a range of values, between the adjacent contour lines. For example, on a map with a 20 ft contour interval a house could be interpolated as having an elevation of about 32 ft or be reported as having an elevation of 21-39 ft. Exact elevations are given for selected spots on many topographic maps. Such elevations are shown using the following tools: bench mark - a point on a map where the elevation is given to the nearest foot and a bronze disk is placed at the location. The disk is intended for use by future surveyors or interested parties. These points are usually represented by a triangle or an X on a map, with a number next to it. On the map a benchmark might appear as: X BM 2031, in which case the ‘BM' denotes bench mark and the number 2031 is the elevation of the benchmark. In the field, finding a bench mark shown on map can be a difficult task. Most benchmarks are affixed to rock outcrops, buildings, or cement anchors. spot elevation - a point on a map where the elevation is given to the nearest foot. Spot elevations are found atop summits, major landmarks, or convenient points. On a map, a spot elevation may appear as: X 3281. If an elevation value is given beside a road junction or similar confluence of streams, paths, etc... the elevation is a spot elevation for the intersection of the map features. water surface elevation - the mean elevation of the surface of a body of water, such as a lake, may be given. The elevation of the water surface will be shown on the surface of the water body. Introduction – Section 2 Coordinate Systems: There are many different systems for specifying positions on the earth's surface. The importance of such systems should be obvious. If you wish to precisely refer a person to a particular point, say a cave entrance, you could try and describe to them where the entrance lay on a map or you could simply give them the coordinates that specify the location. Use of common coordinate systems removes the uncertainty associated with verbal descriptions. The most commonly used coordinate systems are: latitude and longitude, Universal Transverse Mercator (UTM), and township and range. Each is essentially an imaginary grid, or network of lines used to express the position on the earth's surface. Positions are determined and expressed in a manner similar to that of X-Y points on grid paper. With the advent of Global Positioning Systems (GPS), UTM and latitude/longitude positions are more in use today than ever before, though we will focus on latitude/longitude in this exercise. Latitude and longitude The latitude/longitude coordinate system utilizes an imaginary, grid of lines called meridians of longitude and parallels of latitude (see Figure 1). Lines of longitude run north-south between the poles. Lines of latitude form parallel east-west rings across the globe. The equator is assigned 0o degrees latitude. Latitude increases as one gets closer to a pole. The north pole has a latitude of 90o N(orth) and the south pole has a latitude of 90o S. Note that while latitude lines run east-west, they measure all positions relative to north-south. Longitude lines run around the earth in a north-south direction through the poles, but they measure distance east- west of the Prime Meridian. The Prime Meridian passes through Greenwich, England, a city near London. The Prime Meridian is assigned 0o longitude. Longitude values increase from 0o to180o as one moves east of the Prime Meridian and decrease from 0o to -180o to the west. They may also be represented as 0 E to 180 E and 0 W to 180 W. Because the earth is a sphere, longitude values achieve their highest values on the side of the earth opposite the Prime Meridian. Note that longitude lines are not rings. Longitude lines are arcs beginning and ending at the poles. The latitude/longitude coordinate system uses degrees. Latitude is actually the vertical angle from the equatorial plane to any place on the earth, while longitude measures the horizontal angle between that same position and the plane of the Prime Meridian (see Figure 1). Remember that distances around a circle are measured in degrees, with 1 revolution (circle) = 360 degrees. However, when you consider that the earth's circumference at the equator is 24,860 miles each degree must represent 69 miles! If you were to give someone the longitude and latitude of a point to the nearest degree they would know the location within about 49 miles (an area of roughly 9600 miles). Obviously, we need still more information to precisely locate a point on the earth's surface. Therefore, degrees are further divide into minutes and seconds. Degrees and minutes are divided into 60 increments. Thus, 1 degree equals 60 minutes and 1 minute equals 60 seconds. These proportions are also written using symbols: 1o = 60', and 1' = 60", respectively. The division of units is very similar to time on a clock. Figure 1: the globe and latitude/longitude Topographic maps usually cover only a small area of the globe (2 degrees of latitude and longitude, or less). On topographic maps where longitude and latitude are less than a degree, they are given in minutes and seconds. For example, 75° 35' 15" means seventy-five degrees [75°], thirty-five minutes [35'], and fifteen seconds [15"]. These readings of longitude and latitude are given at the corners of each topographic map, with smaller subdivisions, usually in minutes and seconds shown along the map edges (Figure 2). Note that a compass direction MUST be included with a latitude reading and can also be included with a longitude reading. For instance a latitude of 39° 23" 56' could be north or south of the equator. Latitude is either N or S, and longitude is E or W. Actual determination of longitude/latitude points on a map requires: 1. Finding reference ticks on the map with given values of longitude and/or latitude that lie on both sides of the point of interest (note that the degrees are left off on some tick marks so make sure these are added back on when noting the latitude and longitude coordinates) 2. Measurement, with a ruler, of the location of the point of interest relative to the reference ticks. 3. Estimation of the point’s latitude and longitude. Figure 2: latitude and longitude values as presented on a topographic map Points to Ponder: Because the earth is a spheroid, longitude lines converge at the poles. Thus, the distance between longitude lines is greatest at the equator and least at/near the poles. Latitude lines are not affected because they run east-west and are evenly spaced rings. As a result, a map covering a 1° X 1° area at the equator would be roughly square. A 1° X 1° from near a pole would be a very tall rectangle or sliver! For mid-latitudes, such as the contiguous United States, such a map would be a rectangle whose height is slightly greater than its width. Because of the systematic distortion of longitude line spacing, the grid of latitude/longitude lines is not rectangular. The boundaries of mass produced USGS topographic maps are coincident with longitude/latitude lines. For instance, the popular 7.5 minute topographic quadrangle series divides the contiguous United States into 7.5" X 7.5" areas. The USGS also prepares 1° X 2° and 15" X 15" maps. You should now be able to order these maps according to the amount of area each covers, their relative scale (small to large), and levels of resolution and detail. Introduction – Section 3 Information contained on topographic maps: Topographic maps contain a wide variety of information about landscapes. The following are a few of the more general, but important values that can be determined using a topographic map. Height (or depth) - the difference in elevation between the highest point and the lowest point of a local feature (e.g. a hill). For example, a hill with whose base lies at an elevation of 1000 feet and whose top lies at an elevation of 1200 feet is 200 ft high. People commonly refer to the height of a mountain as the elevation of its summit; do not confuse these two meanings! We will strictly refer to height as the distance between the elevation of the base of an object and its summit. If this seems confusing, remember that a six-foot tall woman always has a height of six feet whether she is standing on a beach at sea level or atop a 14,000-foot peak. Relief - the difference in elevation between the highest and lowest points in a region or map. Low relief is usually 10's to 100's of feet of difference and is found where the topography is relatively flat (e.g. a coastal plain). Moderate relief is 100's to 1000's of feet (e.g. Appalachian Mountains). High relief is 1000's to several 1000's of feet and is found where the topography is steep with large changes in elevation over short distances (e.g. Rocky Mountains). Extreme relief is many 1000's of feet (e.g. Everest). Additional Definitions: North symbols: True Geographic North – location of the spin axis (beneath the North Star, map arrow with a star) Magnetic North – location that the needle of a compass will point (arrow labeled MN; in this case, magnetic north declination is 10 degrees West) Grid north – location of north at the center of the US grid (arrow labeled GN) Representative Fraction Scale – The size of the map. A 1:24,000 scale map is 24,000 times smaller than the place it represents (refer to Week 1 Lab: Map Scale for more information if needed). Quadrangle – a typical USGS 7.5-minute topographic map is called a quadrangle map. It’s name can be found in the upper right-hand corner of the topo map. Adjacent quadrangle names are located along the margins of the map or in a box diagram at the bottom of the map. Introduction – Section 4 Reading or making a Contour Map: contour maps are a means of showing a three-dimensional surface on a two-dimensional piece of paper or computer screen. Where a simple map (e.g. a road map) shows only horizontal relationships, contour maps show vertical relationships as well. As with road maps, the relative location of objects in east-west, north-south dimensions are shown on contour maps. However, contour and topographic maps also display earth's third dimension: elevation. Elevation is conveyed by contour lines (discussed previously). By reading the values of contour lines an experienced map user can actually visualize the three-dimensional landscape the map represents (Figure 3). Here are a few tips to help you read topographic map contours: 1. Contour lines connect points of equal elevation; therefore every point along a contour line is the exact same elevation. 2. Both hills and depressions are represented by contour lines in the form of concentric contour lines (Figure 4). In order to distinguish hills from depressions, small marks, called hachures, are drawn on the contour lines within a depression (Figure 4). 3. Contour lines bend across streams. The bend is usually so sharp that the contour forms a ‘V' across the stream. The ‘V' points upstream (Figure 5). 4. The closer the contours, the greater the gradient or relief of an area (e.g., a hill or cliff). Contours that are far apart indicate flatter land. Figure 3: a picture showing how the contour lines translate into shape of the land surface. The top drawing shows the land surface with contours superimposed; the bottom drawing shows contours on a map view of the land. Note how the two drawings relate. A. B. Figure 4: hills and depressions form bulls-eye patterns, however, the depression is illustrated with hachure marks as shown in B. Figure 5: contour lines typically “V” upstream. Common USGS Topographic map symbols: Reading Contour Maps 1. What is the contour interval of this map? ______________ meters (1 point) 2. Using the information provided and the above map, interpolate (estimate) the elevation of the following locations (the x marks the location spot), and assume the units are in meters: (3 points) A. ____________ B. ____________ C. ____________ D. ____________ E. ____________ F. ____________ Answer the following questions using the Week 4 - Mount St. Helens map provided in Doc Sharing. (1 point each) Border of the Map 3. Who published this map? ____________________ 4. What is the publish date of this map?_____________________ 5. How much difference is there between magnetic north and geographic north on this map (in degrees)? ________________ 6. If you were to leave this map and need to find the quadrangle map immediately adjacent to the southwest what is the name of the map would you need to look up?_____________ 7. What are the units for the contour interval?________________ 8. Why do they call this map a 7.5-minute map?__________________ 9. What is the latitude and longitude of the northern peak of Butte Camp Dome found on the west side of the map (to the nearest 30” mark)? _____________________________________ Map Symbols 10. What are the green shaded areas on the map? _____________ 11. What are the blue line features? ______________ 12. What are the blue vegetation symbols in the lower right corner? ______________ 13. What are the areas shown with blue outlines and blue contour lines? _______________ 14. What are the brown speckles found along the upper map margin? _______________ Contours 15. What is the highest elevation along the rim of the 1980 crater of Mount St. Helens (don’t forget the units)? ____________ 16. What is the height of the hill in the very southeast corner of the map (south of the paved road with a benchmark of x3350) as measured from the flat plain to the hill peak? ______________

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