Chapter 1: Introduction to
Earth
McKnight’s Physical Geography:
A Landscape Appreciation,
Tenth Edition, Hess
Introduction to Earth
•
•
•
•
•
•
•
•
•
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
© 2011 Pearson Education, Inc.
2
Geography as a Field of Learning
• Definition
– “Earth Description”
– Geo = earth
• Many sciences
branch from
geography
• Physical versus
cultural
• “Why what is where
and so what?”
© 2011 Pearson Education, Inc.
3
Science and Geography
• The Scientific Method
–
–
–
–
–
–
Observe phenomena
Formulate a hypothesis
Design an experiment
Predict the outcome of the experiment
Conduct the experiment
Draw conclusions
• Scientific “proof”
© 2011 Pearson Education, Inc.
4
Science and Geography
• Measurement Systems
– Need measurement
systems to quantify
scientific processes
– SI versus English units
– Conversions
© 2011 Pearson Education, Inc.
5
The Environmental Spheres
• Four primary spheres
1.
atmosphere— air around us
•
2.
lithosphere— rock and soil, solid
part of the earth
•
3.
Litho = Stone
2
4
3
hydrosphere— water in all its
forms
•
4.
1
Atmo = Air
Hydro – water
biosphere— all living things,
plants, animals, bacteria, viruses
•
Interactions between the spheres
Bio = Life
No part exists independently of the others!
© 2011 Pearson Education, Inc.
6
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
© 2011 Pearson Education, Inc.
7
The Solar System
Figure 1-5
© 2011 Pearson Education, Inc.
8
The Size and Shape of the Earth
• Earth’s Physical
Characteristics
– Oblate spheroid
• Approximate diameter 7900
miles
• Bulges at equator, flattened at
poles
– Equatorial diameter ~ 7926
miles
– Polar diameter ~ 7900 miles
• Circumference of 24,900 miles
© 2011 Pearson Education, Inc.
9
Eratosthenes
Measured the circumference of the earth in 247 BCE
His circumference 26,700 miles – actual 24,900 miles
Used simple geometry and trigonometry!
© 2011 Pearson Education, Inc.
10
Maximum Relief
• Difference in elevation between highest
and lowest points on earth
• Total difference is 65,233 feet
• Top of Mt. Everest 29,035 feet above
sea level
• Bottom of Mariana Trench 36,198m
feet below sea level
If the earth were a
basketball, Mt.
Everest would be
one of the little
pimples on the
surface!
© 2011 Pearson Education, Inc.
11
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 - the grid system
© 2011 Pearson Education, Inc.
Figure 1-9
12
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 (arc)
Airplane routes are
Great Circles
– Circle of illumination - Division
between daylight and darkness
– Small circles – all others
© 2011 Pearson Education, Inc.
Figure 1-10
13
Example of Geographic Grid
Each point of earth’s
surface has a
unique intersection
of the grid lines
Uses a coordinates
system with X and Y
axis
© 2011 Pearson Education, Inc.
14
The Geographic Grid
• Latitudes
– Parallels
– angle north or south of the
equator
• ¼ of 360 degrees = 90 degrees
• From Equator to Pole
– 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)
Know these!!
© 2011 Pearson Education, Inc.
Figure 1-12
15
Latitude Zones
• Tropics
– Hot, wet climate
– Between Tropics of Cancer and Capricorn
– 23.5 N and 23.5 S, with Equator in the middle
• Mid-Latitudes
– Temperate climate
– Between Tropic of Cancer and Arctic Circle (N)
– Between Tropic of Capricorn and Antarctic Circle (S)
• Polar
– Cold, dry climate
– North of the Arctic Circle (N) and south of the Antarctic Circle (S)
© 2011 Pearson Education, Inc.
16
The Geographic Grid
• Longitudes
– Meridians
– Prime Meridian (0° longitude) located
at Greenwich, England
• Zero Degrees = Prime Meridian
• 180 Degrees = International Date Line
• ½ of 360 degree circle is 180 degrees
– Measures as angle east or west of the
Prime Meridian
• Must include “east” or “west” with all
longitude lines except 0 degrees (Prime •
•
Meridian) and 180 degrees
(International Date Line)
© 2011 Pearson Education, Inc.
Figure 1-16
Converge at the poles
Farthest apart at the equator
Longitude Standardized
• Prime Meridian = Zero
degrees longitude
– Goes through Greenwich,
England, a suburb of
London
• Chosen by international
conference in 1880s to
standardize longitude and time
worldwide due to train travel
Height of the British Empire so met
at Royal Observatory – made it the
starting point for longitude.
© 2011 Pearson Education, Inc.
18
Where is Los Angeles?
• Format for
geographic
location
– Latitude, Longitude
Los Angeles: 34°N, 118°W
GPS reading will be more accurate,
down to minutes and seconds!
© 2011 Pearson Education, Inc.
19
© 2011 Pearson Education, Inc.
20
Graticule –
geographic
grid system
of latitude
and
longitude
lines
© 2011 Pearson Education, Inc.
21
Earth-Sun Relations
• Rotation of the Earth
– 24 hours for one rotation (360 degrees = circle)
– Circular motion at all latitudes but the poles
– Rotation is counterclockwise relative to the North Pole
• Rotates toward the EAST
• Reason sun “rises” in the east and “sets” in the west
– Converge at the poles
• Poles in light ½ year, darkness ½ year
– Diurnal transition from light to darkness
• Circle of Illumination – division between light and darkness
– Tidal effects from the Moon and Sun
© 2011 Pearson Education, Inc.
22
• Rotates toward
the east
• Makes one
complete rotation
every 24 hours
• Tilted at
23.degrees from
perpendicular of
the Axis of
Rotation (orbital
plane)
• Where is surface
rotation speed
fastest? Slowest?
© 2011 Pearson Education, Inc.
23
Earth-Sun Relations
• Earth’s Revolution around
Sun
– Rotation vs. Revolution
– One revolution takes 365 ¼
days
– Elliptical orbit
– Aphelion – farthest July 4
– Perihelion – closest January 3
• Average distance 1 AU
Astronomical Unit = 92,955,806
miles
– Round to 93 million miles
Figure 1-19
Earth at perihelion during
Northern Hemisphere winter;
aphelion during Northern
Hemisphere summer
© 2011 Pearson Education, Inc.
24
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
Figure 1-20
» Parallelism (polarity) –
earth does not “wobble”
on its axis
» North Pole always points
toward Polaris (“North
Star”)
© 2011 Pearson Education, Inc.
25
The Annual March of the Seasons
• Three important conditions
– Declination of the Sun
• Where sun is shining 90° to
surface – direct sun
– Solar altitude (angle)
– Length of day
• Two solstices
– June solstice
– December solstice
• Two equinoxes
– March equinox
– September equinox© 2011 Pearson Education, Inc.
Figure 1-22
26
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
© 2011 Pearson Education, Inc.
Figure 1-22
27
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
© 2011 Pearson Education, Inc.
Figure 1-22
28
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
© 2011 Pearson Education, Inc.
29
file:///C:/Users/Marla%20Conti/Documents/
LastToshiba2013/Geography%20101%20B
asics/Old%20McKnight%20Book/Chapter_
01/animations/01-1_EarthSun.html
© 2011 Pearson Education, Inc.
30
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
© 2011 Pearson Education, Inc.
31
The Annual March of the Seasons
• Significance of seasonal patterns
– Spread of solar rays over small and large areas
• Direct sun = smaller area, more concentrated
– Tropical latitudes consistently warmer
• High sun angle, always long days
– Polar latitudes consistently cooler
• Low sun angle, some days sun never rises
– Large seasonal variations in temperature in
midlatitudes
• Many factors, lots of seasonal changes in sun angle,
day length, and location of declination (direct sun)
– Winter – declination of the sun is in opposite
hemisphere
© 2011 Pearson Education, Inc.
32
© 2011 Pearson Education, Inc.
33
© 2011 Pearson Education, Inc.
34
Telling Time
• Three physical measures
of time
– Tropical year - seasons
– Lunar month – new moon
– Solar day – noon to noon, sun at highest
position in the sky
• Solar noon
– Sun casts the shortest shadow
– Pre-modern people used this for time, so all
towns were different
• Ante-meridian (AM—“before noon”)
• Post-meridian (PM—“after noon”)
© 2011 Pearson Education, Inc.
Figure 1-23
35
Telling Time
• Current time system
–
–
–
–
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
© 2011 Pearson Education, Inc.
36
Telling Time
• Time zones of the world
Figure 1-24
© 2011 Pearson Education, Inc.
37
Telling Time
• Time zones of the United States
Figure 1-25
© 2011 Pearson Education, Inc.
38
Telling Time
• Daylight-saving 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
© 2011 Pearson Education, Inc.
39
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
© 2011 Pearson Education, Inc.
40
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
© 2011 Pearson Education, Inc.
41
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
© 2011 Pearson Education, Inc.
42