GEO 101
Introduction to Earth &
Geographic Grid
What is Geography?
January 16, 2010
Geography defined
Four components of the earth system
Lithosphere
Hydrosphere
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Atmosphere
Milky Way: our galaxy
Biosphere
Our solar system is part of the Milky Way Galaxy
Our Sun, a medium sized star, is the central
body of our solar system
One of billions of
galaxies
Spiral galaxy of
over 200 billion
stars
100,000 light
years in diameter
Eight planets in our solar system
+ moons, asteroids, and comets
Inner planets:
Classification of planets
Are generally denser and more nearly spherical than
outer planets
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Outer planets:
Back to Earth
Gas giants do not have solid surface, just get denser
with depth, high velocity winds, may have rocky cores
Earth
• Earth is 1 of 8 planets that is part of
our solar system
Earth questions
What does the Earth look like?
– 93 million (93,000,000) miles away from
the Sun
• This fact was the $1,000,000 question on “Who
Wants to be a Millionaire?”
How does the Earth move around the sun?
Earth facts (cont.)
Earth and The Geographic Grid
• Highest Point:
Latitude and Longitude
• Lowest Point:
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The Geographic Grid
The Earth is a sphere, where do we start?
• The Earth rotates so we can use the
Earth’s rotational axis
– Best points to use are the ends of the
rotational axis
– North & South Poles
Hemispheres
What is the Earth’s rotational
axis?
• Invisible line that
runs through the
center of the Earth
– Northernmost pointNorth Pole
– Southernmost pointSouth Pole
Is the Earth’s rotational axis tilted?
By how much?
Circle of Illumination
Latitude and Longitude
Latitude and Longitude…finding your way
Most common locational system
Measures angular distance in degrees,
not distance in miles or km
Basic geometry: circle has 360 degrees
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Plane of the Equator
Lines of latitude
measure the
(degrees)
of the
.
Expressed in degrees, minutes, and seconds
60 minutes in 1 degree
60 seconds in 1 minute
• Plane passing through Earth halfway
between the Poles and perpendicular to
the axis of rotation
– Where the plane touches the Earth is the
Equator
The lines themselves run __________
Also called
Range from
Latitude of Mobile ≈ 30° 42’ N.
Latitude (cont.)
Latitude can be used to approximate
distances based on following:
360° in a circle
≈ 25,000 miles around earth
25,000 miles / 360° ≈ 69 miles in 1°
One degree of latitude always ≈ 69 miles
This is true because parallels of latitude
stay same distance apart
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LONGITUDE
Meridians of longitude
Arbitrary starting place at Greenwich (London), England
180° = International Date Line
measure the ___________________
of the
.
Expressed in degrees, minutes, and seconds
60 minutes in 1 degree
60 seconds in 1 minute
East
West
N P
Lines of longitude run
Also known as
Range from
0° = Prime Meridian
Longitude of Mobile ≈ 88° 3’ W.
One degree of longitude does NOT = 69 miles,
except along the Equator.
Longitude lines do not stay the same distance
apart. They are closer together near the poles
than at the Equator.
Latitude
Longitude
Geographic
Grid or
GRATICULE
Location of any place on earth can be expressed in
latitude / longitude.
Examples:
Mobile, 30° 42‘ N, 88° 03‘ W
Sydney, Australia, 33° 55‘ S, 151° 17‘ E
Anchorage, Alaska, 61° 12‘ N, 149° 48‘ W
Must include designation N, S, E, or W
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