Topographic Maps TOPOGRAPHIC MAPS

Topographic map is a model, which attempts to show a 3-D world in a 2-D format.

Topographic Map History Products of the U. S. Geological Survey (U.S.G.S.) goal was to provide complete topographic map coverage of the U.S. more than 54,000 maps have been made –entire area of the 48 contiguous States and Hawaii.

USGS Topographic Maps Topo. maps show natural features of the land: –rivers, lakes, swamps –swamps, cliffs, quarries –mountains, valleys, parks and man-made features of the land: –Buildings, houses –Railroads, bridges –roads

Appendix Text book page 697

Natural features

Bathymetric or Water features

Topographic maps are used for… engineering, energy exploration, natural resource conservation, environmental management, public works design, commercial and residential planning, and hiking, camping, and fishing Because engineers, highway officials, land use planners, and other professionals use USGS topographic maps as tools, map accuracy is vital. Dependable maps are also important to campers, hikers, and outdoorsmen.

Topographic Maps They are one of the most widely used maps –distinguishes from other maps CONTOUR lines SHOW the shape and elevation of the land. –They show the 3-D ups and downs of the terrain on a 2-D surface.

On a contour map, hills are shown as a series of curved brown lines called CONTOUR LINES Where is the land FLAT? Where is it HILLY?

Match the contour map with the profile map BEDCFABEDCFA

Contour Lines Are a type of “isolines” prefix iso- means same They are always closed loops that don’t cross. Always brown for land or blue for water. They connect points that are at the same height above or below sea level. example, a 20 foot contour line connects all places on the land that are exactly 20 feet above sea level. 20

Contour Lines Show the shape of the Earth's surface. the terrain / topography. Show the high and low areas: relief Show the elevation of land –possible to measure the height of mountains, –depths of the ocean bottom, and –steepness of slopes.

Profile view Overhead or bird’s-eye view

Very close contour lines Very steep slope Contour lines are …. very far apart – not closely spaced. The land is very flat here.

Contour Interval This is the vertical distance between adjacent contour lines. Most topographic maps have a contour interval of 20 feet or 40 feet (100 feet in very steep terrain, like mountains, 5 or 10 feet in flat terrain, like farmland)

What is the contour interval on this map?

Index contours

Depression Contours A contour that indicates a hole and is represented by a "hachured" brown line. A depression is a point inside a contour that is lower than the contour;

What is the contour interval? What is the elevation of points A and B? A= _____________ ft B= ____________ft ft 100 ft

Contour lines form a “V” and bend upstream when they cross a river or stream. The contour lines bend uphill toward the source of the river.

Scale Most topo maps are produced at a scale of 1:24,000 Also known as 7.5-minute quadrangle maps –each map covers a four-sided area of –7.5 minutes of latitude and 7.5 minutes of longitude. The United States has been systematically divided into quadrangles, all the adjacent maps can be combined to form a single large map!

Math Time! Find the Latitude (upper right corner ) ____º _____’ ____” Find the latitude (bottom right corner) _____° _______’ ______” Subtract. _______’ ______” How many minutes of distance does this map show? *Bonus: How many miles is that? (Hint: 1° of latitude = 65 miles) ______________miles Do the same for longitude. How many minutes of distance does it show?

Alaskan Scale Because of its LARGE land area and sparse population, the primary scale for mapping Alaska is 1:63,360 (1 inch = 1 mile). Each Alaska quadrangle map covers 15 minutes of latitude and longitude There are 2,700 maps in the Alaska 15-minute quadrangle series.

So far…. You should know.. What a topographic maps is How to draw and interpret contour lines, How to determine contour interval, index contour See slope by the spacing of contour lines Understand map symbols and colors Use a map scale to measure distance Find the source of river flow by the direction that contour lines bend.

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SLOPE can be determined by the spacing of the contour lines. But how STEEP is the slope of the terrain?

Finding the Slope or gradient of the terrain on a topographic map. Slope = Elevation between two points distance between two points Slope = Rise Run

Rise (elevation) = 3900 meters Run (distance) = 5 km What is the Slope = ?????

Rise in elevation = 3900 m Running distance 5 km Slope or gradient = For every kilometer you hike, you are climbing up 780 meters (about 2300 feet or 23 stories) in elevation! WOW, that’s a steep climb! 780 m/km

What would the profile of this land feature look like from A to B? A B

Devil’s Tower, WY.