Topographic Map Method

8/13/2019 Topographic Map Method

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TOPOGRAPHIC MAPS

Topographic maps are graphic representations

of the surface of the Earth. They provide:

a plan (bird's-eye) view of the land

scalesto measure ground distances

bearingsto indicate directions

coordinate systems to locate features

symbolsfor natural and cultural features contour lines to show the elevation, slope,

and reliefof the landscape


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SCALES

A scaledefines the ratio between distance on a

map and corresponding distance on ground.

fractional scale: numerical expression

eg: "1:1000" indicates that 1 unit of distance on maprepresents 1000 of the same units on the ground

verbal scale: written description

eg: "1 cm to 1 km"

graphic scale: calibrated bar or line


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BEARINGS

Bearing: the direction

between two points.

True north: the bearing

toward geographic north,

where axis intersects the

Earth's surface

Magnetic north: bearing

toward magnetic north

pole


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COORDINATE SYSTEMS

Two types of coordinate systems arefound on most topographic maps:

latitude-longitude

township-range

The latitude-longitude system isuniversally used throughout the world. The

township- range system is only used inwestern and southern states.


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LATITUDE-LONGITUDE

The Earth's surface is divided by an imaginerycoordinate grid. This grid is defined by two kinds of lines: latitude(or parallels): run east-west

longitude(or meridians): run north-south

The location of any point on the Earth's surface can beindicated by the numbers (coordinates) of the line oflatitude and line of longitude that cross it.

The coordinate numbers of latitude and longitude areangular measurements: coordinate of any line of latitude: angle between line and equator

coordinate of any line of longitude: angle between line and primemeridian


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The coordinate angles aremeasured in units of degrees,minutes, and seconds:

1 degree () = 60 minutes (')

1 minute (') = 60 seconds (")

Topo maps usually come intwo sizes:

7.5' quadrangle: whichextend 7.5' (1/8) of latitudefrom north and south and 7.5'

of longitude from east to west 15' quadrangle: which extend

15' (1/4) from north to southand from east to west


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MAP SYMBOLS

Topographic maps use a variety ofsymbols to show the location ofphysiographic and cultural features, the

type and density of vegetation, and theelevation of the land.

The standard symbols (established by theUnited States Geological Survey) areshown in Table 5-1.


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CONTOUR LINES

Topographic maps are distinctive from other maps in the use ofcontour lines to show the elevation, relief and slope of the land. elevation: vertical distance from sea level

relief: difference in elevation between two points

slope: change in elevation over a given horizontal distance

Contour lines: imaginary lines connecting points of equal elevation. Contour interval: difference in elevation between two adjacent

contour lines: usually constant on any given map

every contour line is a multiple of

the contour interval

Index contour: every fifth contour line is printed thicker, and thenmarked with its elevation for reference.


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READING CONTOUR LINES

*

1. Every fifth line in a series of contours in an index contour (seepoint A on Figure 5-7)

2. The elevations of specific points are noted by benchmarks(seepoints B and C)

3. The elevation of any point on a contour line is equal to theelevation of that contour line:

What is the elevation of point D?

4. The elevation of any point that lies between two contour lines isestimated on the basis of its relative distances from these lines.

What is the elevation of point E?

5. The spacing of contour lines is proportional to the slope of theland.


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6. Every point enclosed by a solidcontour line is topographicallyhigher than the line itself. Solid contour lines enclose topographichighs(see point J).

7. Contour lines which cross rivers and valleys form Vs that point inthe upstream direction (point L).

8. Hachured lines are used to mark the contours of closeddepressions with no outlets such as ponds (see point K)

9. Every point enclosed by a hachured contour line istopographically lower than that line.

10. The outer hachured contour line around a topographic low hasthe same elevation as the closest solid contour line.


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TOPOGRAPHIC PROFILES

Topographic maps provide a plan view of

the shape of the Earth's surface.

A different perspective on the shape of the

Earth's surface is the cross-section view,

called a topographic profile.

The creation of a topographic profile is

shown in Figure 5-8.


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VERTICAL EXAGGERATION

Vertical exaggeration (VE): the distortion of thevertical scale of a topographic profile to

emphasize the relief and slope of the land. VE = vertical scale divided by horizontal scale

For example, the vertical scale in Figure 5-8c is

1"=100'; the horizontal scale is 1"=1000'.

Slope = Relief(Between Two Points)/ Horizontal Distance


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Mapping and Scales


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Maps Latitude lines run

parallel to the equatorand are measured Nand S.

Longitude linesintersect at the polesand measure E andW.

There are 60 minutesin one degree and 60seconds in oneminute.


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Topographic Maps

Measure changes in elevation

A profile is a side view of an elevation

When contour lines are close together, the area is steep.

Contour lines always point upstream (opposite of flow)

Depressions or holes are identified by lines within a circle

Valleys will have contour lines very spread apart


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Topographic Profile

By transferring

information from atopographic map to

another sheet of paper, it

is possible to draw a

landforms profile, orshape.


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Map Scales

Map scale is the relationship betweena unit of length on a map and thecorresponding length on the ground.

Types of Map Scales

Verbal scale expresses in words arelationship between a map distanceand a ground distance. (One inch

represents 16 miles. )

A graphic scale, or bar scale showsdirectly on the map the correspondingground distance.

A representative fraction, or RF,shows the relationship between one ofany unit on the map and one of thesame units on the ground. (1:24,000)

In the above example, 1 cm on themap would equal 24,000 cm in realityon earth

A graphic scale

Ph i l P ti f


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Physical Properties of

Minerals

You can identify minerals by their physical properties tests)


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Specific Mineral Information

Minerals are nonrenewable resources.Silicates are the most abundant mineral group.An ore is a material that is useful and profitable.

Pyrite Hematite Magnetite

HaliteGraphite

Sulfur


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Ye Olde Rock Cycle

I R k


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Igneous Rocks

Igneous rocksform from thecooling andcrystallizationof molten rockmagma, lava)

Intrusive Igneous Rocks

slow cooling of magma inside the Earth. Coarse-grainedtexture (large crystals) GRANITEExtrusive Igneous Rocksquick cooling of lava outside the Earth. Small crystals andfine-grained texture. May look glassy or have holes present. PUMICE, OBSIDIAN,BASALT

M t hi R k


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Metamorphic Rocks

Metamorphic Rocks areformed from heat andpressure on existingrocks.

Contact metamorphismsmall area in contact with anigneous intrusion b kes therock and changes it.Regional metamorphismlarge area changed due toheat and pressure. Usuallywith mountains.

Foliated texture shown)bands or layers of minerals. SCHIST,SLATE, GNEISSNonfoliated textureno layers. These rocks have made a completeatomic change. MARBLE, QUARTZITE


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Weathering, Erosion, and Deposition

Mechanical Weatheringbroken down

Into pieces without a chemical change

Frost (Ice) Wedging

Chemical Weatheringchanged into

Something chemically different

Oxidation (rust)

Erosionthe breakdown and transport of Earth materials by wind, water, gravity,glaciers. Erosion is greatest in high relief areas (steep). Greatest agent of erosion is

water. Glaciers erode by plucking, wind erodes by abrasion and deflation, and gravitycreates mass movements like slump, creep, mudflows, and rockslides.

Depositionthe dropping of Earth materials after energy of motion of agent of erosiondecreases to the point where it cannot carry materials any longer. Deposition is greatest

in low relief areasflat and low and at sea level.

D iti l L df


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Depositional LandformsDELTA

ALLUVIAL FAN

BARRIER ISLAND

BEACHES AND DUNES

Sediment Sizes


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Sediment Sizes

Smallestclay then silt then sand then gravelsClay is the smallest, so it will settle out last. Gravel is the largest, so it will settle outfirst.Sediments will settle out when there is no longer enough energy of motion to carrythem.

Sedimentary Rock Trivia:*Limestone is the only rockformed in 2 different wayschemical and organic)*The 3 major rock resourcesof Virginia are Limestone,Coal, and Titanium*Coal formationPEATchanges to LIGNITE whichchanges to BITUMINOUSwhich changes toANTHRACITE the hardestcoal)

Documents

Topographic Map Method