Download Chapter 1: Introduction to Earth

Chapter 1: Introduction to
Earth
McKnight’s Physical Geography:
A Landscape Appreciation,
Tenth Edition, Hess
Introduction to Earth
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Geography as a Field of Learning
Science and Geography
The Environmental Spheres
The Solar System
The Size and Shape of Earth
The Geographic Grid
Earth-Sun Relations
The Annual March of the Seasons
Telling Time
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Geography as a Field of Learning
• Definition
• Sciences which
branch from
geography
• Physical versus
cultural
• “Why what is where
and so what?”
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Science and Geography
• The Scientific Method
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Observe phenomena
Formulate a hypothesis
Design an experiment
Predict the outcome of the experiment
Conduct the experiment
Draw conclusions
• Scientific “proof”
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Science and Geography
• Measurement Systems
– Need measurement
systems to quantify
scientific processes
– SI versus English units
– Conversions
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The Environmental Spheres
• Four primary spheres
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2.
3.
4.
atmosphere—“air”
lithosphere—“stone”
hydrosphere—“water”
biosphere—“life”
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Interactions between the spheres
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The Solar System
• Formation of the Solar
System
– Formed 4.5 to 5 billion years
ago
– 8 planets revolve around the
Sun
– 4 terrestrial planets
– 4 gas giants
– Earth is the third planet
Figure 1-4
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The Solar System
Figure 1-5
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The Size and Shape of the Earth
• Earth’s Physical
Characteristics
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Equatorial diameter ~ 12,756 km
Polar diameter ~ 12,714 km
Circumference of 40,000 km
Maximum relief
Figure 1-6
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The Geographic Grid
• Location on Earth
– Need an accurate location on
Earth to describe geographic
features
– Use Earth’s rotation axis to base
location on the surface
– North Pole and South Pole
– Plane of the Equator—halfway
between poles and
perpendicular to Earth’s surface
– graticule
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Figure 1-9
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The Geographic Grid
• Great Circles
– Circles which bisect a
sphere and pass through
the sphere’s center
– Identify the shortest
distance between two points
on a sphere—great circle
distance
– Circle of illumination
– Small circles
Figure 1-10
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The Geographic Grid
• Latitudes
– Parallels
– angle north or south of the
equator
– 7 important latitudes:
– Tropic of Cancer and Capricorn
(23.5° N and S)
– Equator (0°)
– Poles (90° N and S)
– Arctic and Antarctic Circles
(66.5° N and S)
– Latitude zones
Figure 1-12
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The Geographic Grid
• Longitudes
– Meridians
– Prime Meridian (0° longitude)
located at Greenwich, England
– angle east or west of the Prime
Meridian
– Converge at the poles
Figure 1-16
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Earth-Sun Relations
• Rotation of the Earth
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24 hours for one rotation
Circular motion at all latitudes but the poles
Rotation is counterclockwise relative to the North Pole
Converge at the poles
Diurnal transition from light to darkness
Tidal effects from the Moon and Sun
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Earth-Sun Relations
• Earth’s Revolution around
Sun
– One revolution takes 365 ¼
days
– Elliptical orbit
– Aphelion (152,171,500 km)
– Perihelion (147,166,480 km)
– Average distance
(149,597,892 km)
Figure 1-19
– Earth at perihelion during
Northern Hemisphere winter;
aphelion during Northern
Hemisphere summer
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Earth-Sun Relations
• Orbital Properties
– Plane of the Earth’s orbit is the
plane of the ecliptic
– Earth’s axis tilted at 23.5°
– Plane of ecliptic is not parallel
to equatorial plane
• Polarity of the Earth’s axis
– Parallelism
– North Pole always points
toward Polaris (“North Star”)
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Figure 1-20
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The Annual March of the Seasons
• Three important
conditions
– Declination of the Sun
– Solar altitude
– Length of day
• Two solstices
– June solstice
– December solstice
• Two equinoxes
– March equinox
– September equinox
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Figure 1-22
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The Annual March of the Seasons
• June solstice
– Occurs on approximately
June 22 each year
– Sun is directly overhead at
23.5° N latitude
– Antarctic Circle in 24 hours
of darkness
– Marks start of summer in
Northern Hemisphere;
winter in Southern
Hemisphere
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Figure 1-22
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The Annual March of the Seasons
• December solstice
– Occurs on approximately
December 22 each year
– Sun is directly overhead at
23.5° S latitude
– Arctic Circle in 24 hours of
darkness
– Marks start of winter in
Northern Hemisphere;
summer in Southern
Hemisphere
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Figure 1-22
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The Annual March of the Seasons
• Equinoxes
– Occur on approximately
March 21 and September
21 each year
– Day length is 12 hours
worldwide (“equinox”)
– Sun is directly overhead at
the equator
Figure 1-22
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The Annual March of the Seasons
• Day length
– Always 12 hours at the
equator
– In the Northern
Hemisphere, day length
increases after March
equinox
– Maximum day length
during June solstice in
Northern Hemisphere
– Opposite for Southern
Hemisphere
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The Annual March of the Seasons
• Significance of seasonal patterns
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Spread of solar rays over small and large areas
Tropical latitudes consistently warmer
Polar latitudes consistently cooler
Large seasonal variations in temperature in
midlatitudes
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Telling Time
• Three physical measures
of time
– Tropical year
– Lunar month
– Solar day
• Solar noon
– Sun casts the shortest shadow
Figure 1-23
• Ante-meridian (AM—“before
noon”)
• Post-meridian (PM—“after noon”)
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Telling Time
• Current time system
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24 time zones
Greenwich Mean Time (GMT) is standard
Controlling Meridian for each time zone
Several countries have multiple time zones in their
borders
– Time zone boundaries subject to local political and
economic boundaries of different nations
– 180° meridian chosen as the International Date Line
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Telling Time
• Time zones of the world
Figure 1-24
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Telling Time
• Time zones of the United States
Figure 1-25
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• Daylight-saving time
Telling Time
– Move clocks ahead by an hour during the summer months
– Originally done by Germans during WWII; now practiced by many
nations
– Conserves lighting energy by providing an extra hour of daylight
Used
No longer used
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Never been used
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Summary
• Geography is the study of the distribution of
physical and cultural attributes of Earth
• Many sciences have branched off of geography
• The scientific method is important when doing
scientific studies
• Earth has four primary spheres: the atmosphere,
the lithosphere, the hydrosphere, and the
atmosphere
• The solar system formed 5 billion years ago and
consists of 8 planets
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Summary
• Earth is an imperfect sphere
• A latitude and longitude grid help identify
locations on Earth’s surface
• Earth rotates on its axis in 24 hours
• Earth revolves around the Sun in 365 ¼ days
• Tilt of Earth’s axis causes seasons
• Equinoxes and solstices help identify when a
seasonal transition occurs
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Summary
• Time zones were established to have a
uniform global time system
• Daylight-saving time was devised to conserve
energy by adding an hour of daylight
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