1. Chapter 1: Introduction to Earth

2. Introduction to Earth
Physical earth is dynamic and constantly changing – never static
Everything is connected to everything else
Processes
Fast
Slow
Large
Small
Regular
Irregular

3. Geography as a Field of Learning
Greek Meaning - “earth description”
Fundamental questions:
“Why is what where?”
“So what?”
Spatial Distributions
What is Physical Geography?
Distribution & explanation of processes & features of natural origin
How/why physical processes have shaped Earth’s surface
“Why the earth is the way it is”
“Where are the four corners of the earth?”

4. Elements of Geography Interrelationships among elements Physical
Examines Earth elements which are natural in origin
Cultural (Human)
Looks at elements of human endeavor

5. Science and Geography The Scientific Method Scientific “proof”
Observe phenomena
Formulate a hypothesis
Design an experiment
Predict the outcome of the experiment
Conduct the experiment
Draw conclusions
Theory
Scientific “proof”

6. The Environmental Spheres
Physical earth is dynamic & constantly changing
Break the real world up into parts to better understand it.
Simplified parts = systems (spheres)
Everything is connected to everything else
Four primary spheres
atmosphere—“air”
lithosphere—“stone”
hydrosphere—“water”
biosphere—“life” 2 3 1 4
Interactions between the spheres

7. The Solar System Formation of the Solar System Sun
Formed billion years ago
8 planets
4 terrestrial planets
4 gas giants
Sun
Medium sized star
Makes up over 99% of the solar system’s mass
Figure 1-4

8. The Size and Shape of the Earth
Earth’s Physical Characteristics
Not perfectly round
Oblate spheroid
Equatorial diameter ~ 12,756 km
Polar diameter ~ 12,714 km
Circumference of 40,000 km
Figure 1-7

9. The Size and Shape of the Earth
Maximum relief
Mt. Everest = 29,035 ft.
Mariana Trench = 36,198 ft.
Surface differences
Land = 29%
Oceans = 71%
Northern Hemisphere: “Land Hemisphere” (39% land)
Southern Hemisphere: “Water Hemisphere” (19% land)
Figure 1-6

10. 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 & perpendicular to Earth’s surface
Graticule
Figure 1-9

11. The Geographic Grid Great Circles
Cuts the sphere into 2 equal halves (hemispheres)
Must pass through the sphere’s center
Example: Circle of illumination
Small circles
Figure 1-10

12. The Geographic Grid Latitudes 0º-90º N/S Parallels
Connects points of equal latitude
69 miles or 111 km apart
Angle north or south of the equator
Figure 1-11

13. The Geographic Grid Latitudes 7 important latitudes:
Tropic of Cancer (23.5° N)
Tropic of Capricorn (23.5° S)
Equator (0°)
North Pole (90° N)
South Pole (90° S)
Arctic (66.5° N)
Antarctic Circles (66.5° S)
Figure 1-12

14. The Geographic Grid Longitudes 0°-180° E/W Meridians
Prime Meridian (0° longitude) located at Greenwich, England
Longitude is measured E/W of this point
Angle east or west of the Prime Meridian
Converge at the poles
Not parallel to one another
Figure 1-16

15. Earth-Sun Relations Rotation of the Earth 24 hours for 1 rotation
Rotation velocity varies with latitude
At Equator = 1037 mph
At Poles = 0 mph
Rotation is counterclockwise relative to North Pole (West to East)
Rotational influences
Diurnal transition from light to darkness (daylight/darkness)
Tidal effects from Moon & Sun
Coriolis Effect
Figure 1-18

16. Earth-Sun Relations Earth’s Revolution around Sun
One revolution takes 365 ¼ days
365 days, 5 hrs, 48 min, & 48 sec
( days)
Leap Year
Elliptical orbit
Aphelion
During N. Hemisphere summer (~July 4)
Perihelion
During N. Hemisphere winter (~Jan 3)
Perihelion/Aphelion are NOT important factors in seasonal variations
Figure 1-19

17. Earth-Sun Relations Orbital Properties Polarity of Earth’s axis
Plane of the Earth’s orbit is the plane of the ecliptic
Inclination
Earth’s axis tilted at 23.5°
Plane of ecliptic is not parallel to equatorial plane
Polarity of Earth’s axis
Parallelism
North Pole always points toward Polaris (“North Star”)
Figure 1-20

18. Circle of Illumination
Because Earth is a sphere, only 50% can be illuminated by the sun at once
If the axis was perpendicular to the sun’s rays, all points on earth would have 12 hours of daylight/darkness each day
Because of Earth’s tilt, most places experience varying amounts of daylight & darkness throughout the year

19. Solar Declination & Solar Altitude1.
Solar Declination: latitude where sun’s rays strike earth at 90° angle
23.5 N to 23.5 S (Tropics)
Solar altitude: angle sun’s rays hit Earth at noon
Only 1 pt on earth receives Sun’s direct rays at a time
0 when sun is on horizon
90 when sun is directly overhead
Varies by day/season
Omaha: ~25° in Dec; ~72 ° in June 2. 3.
1. Solar altitudes at 50 N (Canadian-US border)
2. Solar altitudes at equator
3. Solar altitudes at South Pole

20. Changes in Daylight
All locations spend 50% of time in daylight & 50% in darkness
Daylight equally distributed every day at equator
Distribution becomes more unequal as you move poleward
Period of daylight varies throughout the year
Shortest day about Dec 21 (Winter solstice)
Longest day about June 21 (Summer solstice)
Opposite in Southern Hemisphere
Day length & solar angle of sun’s rays determine amount of insolation received at any location

21. 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
Figure 1-22

22. The Annual March of the Seasons
June solstice
Approximately June 22
Sun is directly overhead at 23.5° N latitude (Tropic of Cancer)
Antarctic Circle (66.5° S) to South Pole (90° S) in 24 hours of darkness
Arctic Circle (66.5° N) to North Pole (90° N) in 24 hours of daylight
Figure 1-22

23. The Annual March of the Seasons
December solstice
Approximately December 22
Sun is directly overhead at 23.5° S latitude (Tropic of Capricorn)
Arctic Circle (66.5° N) to North Pole (90° N) in 24 hours of darkness
Antarctic Circle (66.5° S) to South Pole (90° S) in 24 hours of daylight
Figure 1-22

24. The Annual March of the Seasons
Equinoxes
Approximately March 21 & September 21
Day length is 12 hours worldwide (“equinox”)
Sun is directly overhead at the equator
Figure 1-22

25. 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

26. The Annual March of the Seasons

27. The Annual March of the Seasons
Significance of seasonal patterns
Spread of solar rays over small & large areas
Tropical latitudes consistently warmer
Polar latitudes consistently cooler
Large seasonal variations in temperature in midlatitudes
23½º N
June 21
Sept. 21
Latitude 0º
Mar. 21
Mar. 21
23½º S
Dec. 21
Time

28. Telling Time 3 physical measures of time Solar noon
Tropical year
Lunar month
Solar day
Solar noon
Sun casts the shortest shadow
Ante-meridian (AM—“before noon”)
Post-meridian (PM—“after noon”)
Figure 1-23

29. Telling Time Current time system (24 time zones)
1 Earth day = 24 hours & 1 full Earth rotation = 360°
Time zones are 15° or 1 hour apart
Ex: 2 points 1 hour apart = 15° apart
Ex: 2 points 15° apart = 1 hour apart
Figure 1-24

30. Telling Time Current time system Greenwich Mean Time (GMT) is standard
Prime meridian 0° longitude
Universal Time Coordinated (UTC)
180° meridian = International Date Line
Cross going east , go to preceding day
Cross going west, go to next day
Figure 1-24

31. 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
Figure 1-25

32. 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
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
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