Models of the
Earth
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
Latitude

Parallels


describes north and
south of the equator
Run east-west
parallel of the
equator
Latitude

Angular north or
south of the equator
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 ‘’
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
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
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
Finding Direction



Use a magnetic
compass
Geomagnetic polesareas of earth’s
surface above
where the poles of
the imaginary
magnet
Needles of compass
points to
geomagnetic north
pole
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
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
Mapping
Earth’s Surface
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
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
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
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)
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
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
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
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)
Isograms
A
line on a map
that represents a
constant or equal
value of a given
quantity
 Meteorologists use
to show
atmospheric
pressure
Types of
Maps
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
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
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
Topographic Maps
 Buildings,
boundaries, roads, and
railroads- normally in black
 Major highways-red
 Bodies of water-blue
 Forest-green
 Contour lines- brown and black
Geologic Maps
 Show
distribution of
geologic features
 Types of rocks,
locations of faults,
folds, etc.
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
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
Soil Maps
 Classify,
map and
describe soils
 Based on soil
surveys
 NRCS (Natural
Resources
Conservation
Service maps soil
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

 Uses-
General map shows the approximate location of
different types of soil within the area
Detailed information about soils
agricultural and land management