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Models of the Earth
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Earth Very nearly perfect sphere
No top, bottom or sides Earth’s axis of rotation can be used to
establish reference points Reference points:
North and South poles Equator divides earth into northern and
southern hemisphere
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Latitude Parallels-
describes north and south of the equator
Run east-west parallel of the equator
Latitude Angular north or
south of the equator
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Degrees of Latitude Measured in degrees Equator is 0° North Pole and South Pole is 90° Each degree consists of 60 equal parts called minutes 1.85 km Symbol is ‘
Each minute is divided into 60 equal parts called seconds Symbol is ‘’
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Longitude Meridian
is a semicircle that runs from pole to pole
Prime meridian is 0° Longitude-
is the angular distance east or west of the prime meridian
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Degrees of Longitude All locations have a longitude between
0° and 180° east or west of the prime meridian
A degree of longitude equals approximately 111 km Decreases as you move towards the pole
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Great Circle Any circle that divides the glove into
halves or marks the circumference of the globe Any circle formed by two meridians of
longitude that are directly across the globe from each other is a great circle
Can run in any direction around the globe Air and sea routes often follow great
circles
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Finding Direction Use a magnetic
compass Geomagnetic poles-
areas of earth’s surface above where the poles of the imaginary magnet
Needles of compass points to geomagnetic north pole
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Magnetic Declination Angle between the direction of the
geographic pole and the direction in which the compass needle points is called magnetic declination.
Measured in degrees east or west of the geographic north pole
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GPS (Global Positioning System) GPS can be used to find their location on
earth Based on a global network of 24
satellites that transmit radio signals to Earth’s surface.
First one was NAVSTAR (launched in 1978)
Can be accurate within 10-15 meters of position
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Mapping Earth’s Surface
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Mapping Globe- model of earth
Accurately represent locations, relative areas, and relative shapes
Useful for large surface features Too small to show details of earth’s
surface
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Making maps Cartography
Scientists who make maps Collect data by a field survey or remote
sensing Remote sensing
The process of gathering and analyzing information about an object without physically being in touch with the object
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Map projections Map is a flat representation of Earth’s
curved surface Area may be distorted in size, shape,
distance or direction Map of a city shows slight distortion Map of earth shows greatest distortion
Map projection A flat map that represents a spherical
surface
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Cylindrical Projections Meridians appear as
straight, parallel lines that have an equal amount of space between them
Advantage: Parallels and
meridians form a grid (locating positions is easier)
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Azimuthal Projections Place a sheet of paper
against a transparent, lighted globe so that paper touches the globe at only one point
Great for air travel and finding great circles
Little distortion at point of contact
Unequal spacing between parallels causes distortion in both direction and distance
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Conic Projections Made by placing a paper
cone over a lighted globe so that the axis of the cone aligns with the axis of a globe.
Touches the globe at a parallel
Where the cone and globe are in contact have the slightest distortion
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Reading a Map North on top, east on the right, south on
the bottom, west on the left Never Eat Soggy Waffles
Parallels run from side to side Meridians run from top to bottom Legend- a list of map symbols and their
meanings
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Map Scales Scale- the relationship between the distance
shown on a map and the actual distance Graphic Scale- Printed line that has markings
on it that are similar to those on a ruler Fractional Scale- 1:25,000 (one unit of
distance represents 25,000 of the same unit on earth
Verbal Scale- Sentence form (One cm is equal to one km)
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Isograms A line on a map
that represents a constant or equal value of a given quantity
Meteorologists use to show atmospheric pressure
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Types of Maps
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Topographic Maps The size and shape
of the land surface features of a region including its relief
Natural features Shows elevation
The height of an object above sea level
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Topographic Maps More detailed information about the
surface Shows size, shape and elevation Contour lines- a line that connects
points of equal elevation on a map (is an isogram)
Relief- the difference between the highest and lowest elevations in a given area
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Topographic Maps Widely spaced contour lines indicate
gradual change in elevation Closely spaced contour lines is a rapid
change in elevation Contour lines that bend to form a V is a
valley Closed loop contour lines indicate a
hilltop
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Topographic Maps Buildings, boundaries, roads, and
railroads- normally in black Major highways-red Bodies of water-blue Forest-green Contour lines- brown and black
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Geologic Maps Show distribution
of geologic features
Types of rocks, locations of faults, folds, etc.
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Geologic Maps Geologic unit- volume of rock of a given
age range and rock type Assigned by color Letters represent age
One capital letter- symbolizes age of rock Lowercase letters- represent the name of
the unit or type of rock
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Geologic Maps Contact lines-indicates places at which two
geologic meet Strikes-indicates direction in which beds run Dips- Indicates the angle at which the beds
tilt Two types of contacts
Faults- cracks where rocks can move past each other
Depositional contacts-show where one rock layer formed above another
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Soil Maps Classify, map and
describe soils Based on soil
surveys NRCS (Natural
Resources Conservation Service maps soil
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Soil Maps Soil Survey
Text- general information about the geology, topography and climate of area being mapped
Tables- describes and volumes of soils in the area
Maps- General map shows the approximate location of
different types of soil within the area Detailed information about soils
Uses- agricultural and land management