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## Topographic Maps

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**Topographic Maps***these notes go on pages 19 AND 21 of your Plate Tectonics INB!!***topography means “shape of the land”**• topographic maps grapha 3D landscape on a 2D surface showing elevation Mount Rainier, Washington**Contour Lines:**• contour lines connect areas of equal elevation above or below sea level • index contours are darker with elevation marked • intermediate are lighter with no elevation**Contour Interval:**• the elevation change that each line represents • FORMULA: distance between index contours ÷ # of contour lines**Water Direction:**• “Rule of V’s”: contour lines make V’s indicating direction of flow of rivers & streams • V’s point uphill • help map reader interpret elevations of intermediate contours around stream**Hills:**• contour lines are increasing in elevation within other contour lines • closer lines are together, the steeper the slope**Depressions**• dips or major holes in land (from sinkholes, volcanoes, etc) • perpendicular contour lines, called hachures, point into depression Lip of depression is highest point**Benchmarks & Colors:**• benchmarks: area of measured elevation in between contour lines (marked by an X or BM) • colors: • brown- contour lines • blue- water • green- forest, woods • black, pink & red- manmade structures**Gradient/Slope**• how steep a hill is (look how close lines are!) • formula: = ∆ in elevation ÷ straight line distance • Units: m/km OR ft/mile**Slope**Steep Slope Gentle Slope**Line A Distance = .5 miles**Elevation Change = Slope =**Topo Map Profile:**• cross sectional view along a line drawn through a topo map • HOW: • make a line through your map & label (X-Y, X-X’, etc.) • use edge of paper and make “ticks” every time a contour line intersects • record elevation next to each tick**X**Y**transfer ticks onto a graph, or graph paper**• connect the dots to get a side view along your line!**Map Projections**• mathematical means of transferring info from 3D to 2D; different “views” • most have flaws because of curved surface • projections & flaws: (1) mercator- distorts areas near poles; view entire world (2) gnomonic- distorts areas away from center point; view poles (3) polyconic- distorts poles & Equator; view mid-latitudes (4) globe- no flaws; view entire world to scale**Gnomonic Projection**Polyconic Projection Mercator Projection Three most common types of map projections are:**Map Distortions**Greenland Mercator map size True size of Greenland**Map Scales:**• mathematical relationship between objects on a map and their true life size • ratio or fraction • larger the number on the right, greater the amount of area map covers • same unit on each side • bar scale gives quick visualization of distances on a map