Download - 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)