Topographic Maps

*these notes go on pages 19

AND 21 of your Plate Tectonics

INB!!*

topography means “shape of the land”

topographic maps graph a 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 SlopeGentle Slope

Line A Distance = .5 miles

Elevation Change =

Slope =

Topo Map Profile:

cross sectional view along a line drawn through a topo map

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 intersects3. 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 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

Mercator Projection

Gnomonic Projection

Polyconic 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 sidebar scale gives quick

visualization of distances on a map

Example: