Chapter 1 with audio

Geography 101:
Physical Geography
Dr. Kevin Law

Chapter 1
Introduction to Earth

Geography as a Field of Learning
 Geography- generalized discipline that
focuses on Earth
– Greek for “earth description”
– Fundamental questions
 “Why is What Where?”
 “So What?”

Geography as a Field of Learning
 Geography’s basic characteristics:
– How things differ from place to place
– Has no body of facts it can call wholly its own
– Broad field of inquiry
– Both a physical and a social science
– Interested in Interrelationships
 Physical Geography
 Cultural Geography

The Environmental Spheres
 Earth’s surface is a complex interface where
4 spheres meet.
– Lithosphere- litho is Greek for “stone”
– Atmosphere- atmo is Greek for “air”
– Hydrosphere- hydro is Greek for “water”
– Biosphere- bio is Greek for “life”

The Solar System
Fig. 1-7
 Solar System- system of
8 planets revolving
around the Sun
– Pluto is a dwarf planet
 Sun- medium sized star &
makes 99% of the solar
system’s mass
 Sun is 1 of 100 billion
stars in Milky Way galaxy,
which is 1 of a billion
galaxies

The Solar System
 Earth’s orbit is nearly the same plane as the
other planets (except Pluto (demoted in
2006))
 Earth, like the Sun, rotates from west to east
on its axis

Why is Pluto not a planet?
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Article
Is Pluto a Planet?
Clip
Clip 2

The Size and Shape of the Earth
 Frame of reference determines whether
Earth is “large” or “small”
 Earth is “oblate spheroid” rather than a
sphere
– Greeks believed Earth was a sphere 6th century
B.C.

 Earth shape affected by
– Bulges in midriff (pliability of lithosphere)
– Topographical irregularities (relatively small)

The Geographic Grid (Fig. 1-12)
 System of accurate
location is necessary
to pinpoint the position
of any spot on Earth
– Grid system- uses
network of intersecting
lines
– Graticule- grid system
for mapping Earth that
uses parallels and
meridians

The Geographic Grid
Fig. 1-13
– 4 Earth features provide reference
points
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North Pole
South Pole
Rotation axis
Equatorial plane

– Equator- imaginary midline of Earth

The Geographic Grid
Fig. 1-14
– Great Circle- largest circle
that can be drawn on a
sphere, passes through
center
 Circle of Illuminationcircle that divides Earth
between light and dark

– Small Circle- plane that cuts
through sphere

Latitude
Fig. 1-15
 Latitude- distance
measured north and
south of the equator
 Length of 1 degree
latitude varies because
of polar flattening
 Parallel- an imaginary
line that connects all
points of the same
latitude

Key “Latitudes”
Fig. 1-17
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Equator, 0°
North Pole, 90°N
South Pole, 90°S
Tropic of Cancer, 23.5°N
Tropic of Capricorn, 23.5°S
Arctic Circle, 66.5°N
Antarctic Circle, 66.5°S

Length of Degrees of Latitude
and Longitude

Longitude
Fig. 1-20
 Longitude- distance
measured east and west
 Meridian- imaginary line of
longitude extending from
pole to pole
– NOT parallel to each
other
 Prime meridian- passes
through Royal Observatory
at Greenwich, England

Earth-Sun Relations
 Relationship between Earth and Sun vital
because dependent on solar energy
 2 Basic Movements:
– Earth’s daily rotation on its axis
– Earth’s annual revolution around the Sun

Earth’s Rotation on Its Axis
 Earth rotates toward the east (24 hrs)

– Creates illusion celestial bodies rise in the east and set
in the west

 Speed of rotation varies from place to place, but
constant at a given place, so humans cannot
sense
 Rotational effects:

– Coriolis effect- apparent deflection to right
– Locations experience increased/decreased gravitational
pull of Moon and Sun
– Daily alternation of light and darkness

Speed of Rotation of Earth’s
Surface

Earth’s Revolution around the Sun
 Tropical Year- time Earth makes 1 revolution
around the Sun (approx. 365.25 days)
 Earth’s revolution is an ellipse
– Varying Earth-Sun distance does NOT affect seasonal
temperatures
– Perihelion- point Earth is closest to Sun
 ~147 million km (Jan.3)

– Aphelion- point Earth is farthest from Sun
 ~152 million km (July 4)

The Annual March of the Seasons
 Plane of the ecliptic- imaginary plane that
passes through the Sun and through every
point of Earth’s orbit
 Inclination- degree Earth’s rotation axis is
tilted (23.5°)
 Polarity- Earth’s axis always points toward
Polaris, the North Star
 Insolation- Incoming Solar Radiation

Solstices
 Solstice- Occurs twice per year when Sun’s rays strike
northernmost/southernmost latitudes (23.5°N/S)
– Winter solstice, around Dec. 21
– Summer solstice, around June 21

Tropic of Cancer- 23.5°N, perpendicular rays (Jun 21)
Tropic of Capricorn- 23.5°S, perpendicular rays (Dec 21)
Arctic Circle- 66.5°N, 24 hrs of daylight (Jun 21) or
darkness (Dec. 21)
 Antarctic Circle- 66.5°S, 24 hrs of daylight (Dec 21) or
darkness (Jun 21)
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Equinoxes
 Equinox- perpendicular Sun rays strike the
equator (12 hrs daylight)
– Vernal Equinox, March 20
– Autumnal Equinox, Sep 22

Changes in Daylight and Darkness
 Period of daylight vary throughout year
– Increasing north of the equator from Winter
solstice to Summer solstice (Northern Hem.)

 Day length and Sun ray angle determine
insolation amount
– Tropic latitudes are warm because of high sun
angles
– Polar regions cold because of low sun angles

Day Length at Time of June
Solstice

Telling Time- Standard Time
 Use of local solar time created problems
 1884 international conference divided world
into 24 standard time zones, 15 ° long. each
– Universal Time Coordinated (UTC)- formerly
Greenwich Mean Time (GMT); uses local solar
time of Greenwich as standard

The International Date Line
Fig. 1-34
 International Date
Line- marks where
new days begin and
old days exit
– Time difference of 1
day from one side to
other
– Falls on 180th meridian

Daylight-Saving Time
 Clocks are set forward 1 hr to extend
daylight into evening
– Originally created in Germany to conserve
electricity
– AZ, HI do not observe
– Was not designed for farmers
 After all it makes it darker in the morning

Chapter 1 with audio

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