Topographic Maps these notes go on pages 19

Topographic Maps *these notes go on pages 19 AND 21 of your Plate Tectonics INB!!*

Ø topography means “shape of the land” Ø topographic maps graph a 3 D landscape on a 2 D surface showing elevation Mount Rainier, Washington

Contour Lines: Ø contour lines connect areas of equal elevation above or below sea level Ø index contours are darker with elevation marked Ø intermediate are lighter with no elevation

Contour Interval: Ø the elevation change that each line represents Ø FORMULA: distance between index contours ÷ # of contour lines

Water Direction: Ø “Rule of V’s”: contour lines make V’s indicating direction of flow of rivers & streams Ø V’s point uphill Ø help map reader interpret elevations of intermediate contours around stream

Hills: Ø contour lines are increasing in elevation within other contour lines Ø closer lines are together, the steeper the slope

Depressions Ø dips or major holes in land (from sinkholes, volcanoes, etc) Ø perpendicular contour lines, called hachures, point into depression Lip of depression is highest point

Benchmarks & Colors: Ø benchmarks: area of measured elevation in between contour lines (marked by an X or BM) Ø colors: Ø brown- contour lines Ø blue- water Ø green- forest, woods Ø black, pink & red- manmade structures

Gradient/Slope Ø how steep a hill is (look how close lines are!) Ø formula: = ∆ in elevation ÷ straight line distance Ø Units: m/km OR ft/mile

Slope Gentle Slope Steep Slope

Line A Distance =. 5 miles Elevation Change = Slope =

Topo Map Profile: Ø cross sectional view along a line drawn through a topo map Ø HOW: 1. make a line through your map & label (X -Y, X-X’, etc. ) 2. use edge of paper and make “ticks” every time a contour line intersects 3. record elevation next to each tick

X Y

4. transfer ticks onto a graph, or graph paper 5. connect the dots to get a side view along your line!

Map Projections Ø mathematical means of transferring info from 3 D to 2 D; different “views” Ø most have flaws because of curved surface Ø 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 midlatitudes (4) globe- no flaws; view entire world to scale

Three most common types of map projections are: Mercator Projection Polyconic Projection Gnomonic Projection

Map Distortions Greenland Mercator map size True size of Greenland

Map Scales: Ø mathematical relationship between objects on a map and their true life size Ø ratio or fraction Ø larger the number on the right, greater the amount of area map covers Ø same unit on each side Øbar scale gives quick visualization of distances on a map

Example: