1. The Earth as a Rotating Planet
Chapter 1
The Earth as a Rotating Planet

2. The Shape of the Earth Earth or Sun moving? Early sailors view……
Is the Earth a perfect sphere?
(Quasi-sphere)*—Rotation causes it to bulge at the Equator and flatten at the Poles *Oblate Spheroid

3. Earth Rotation What is rotation? Why is rotation important?
What direction does the Earth rotate?
How long does it take to rotate?
3 main effects of rotation
Why is rotation important?
Axis serves as reference for geographic grid (latitude and longitude)
Measure for time (time zones)
Affects physical and life processes

4. Earth Rotation
Figure 1.2 (P. 26)

5. The Geographic Grid What is a geographic grid?
A system for locating or determining the location of places on the Earth’s surface
Demarcations for hemispheres
Latitude-Distance N or S of the Equator (0 degrees latitude) **Parallels
Tucson is approximately 30 degrees North
Longitude-Distance E or W of the Prime Meridian (0 degrees longitude)

6. A few more points about the latitude and longitude...
Location of a point is given as:
latitude (in degrees N or S), longitude (in degrees E or W)
There are two techniques for indicating a more detailed location:
Decimal degrees: °
Degrees, minutes, seconds: 32° 07’ 48”

7. Determining a location with latitude and longitude

8. Parallels and Meridians

9. Examples What city is located at 37°S and 144°E?
Melbourne, Australia
What city is located at 40°N and 105°W?
Denver, CO
What city is located at 51°N and 0°W?
London, England
Distances: Given the fact that the circumference of the Earth is 24,860 miles and there are 360° in a circle—How many miles are there in 1 ° of longitude at the Equator?

10. Calculating Distances between Lines of Latitude
Latitude=(69 miles) x (difference in degrees latitude)
Example 1: Calculate the number of miles between Atlanta (33°N, 84°W) and New York City (40°N, 74°W).
Latitude=(69) x (7°)=483 miles
Example 2: Calculate the number of miles between Prague (50°N, 14°E) and Tripoli, Libya (32°N, 13°E).
Latitude=(69) x (18°)=1,242 miles

11. Calculating Distances between Lines of Longitude (**Difficult)
Longitude=(69 miles) x (COS of parallel traveled) x (difference in degrees long.)
Example 1: Calculate the number of miles between Cairo, Egypt (30°N, 31°E) and New Delhi, India (28°N, 77°E). Assume travel along the 29°N parallel.
Longitude=(69) x (COS 29) x (46°)=2,777 miles

12. Map Projections
A map is just an abstraction or representation of the real world. The art and science of map-making is called cartography.
When you are trying to represent a curved surface on flat paper, you get distortion. Why?
Map units

13. From Earth to a map Start with ellipsoid
Difficult, if not impossible, to take a curved surface and place it on a flat surface
Result is distortion
All maps have some type of distortion

14. Five Types of Distortion +1 more
Type Example
Shape Circle becomes oval
Scale Map scale changes
Area Land mass gets bigger
Distance Space between cities increases
Direction Line varies: N to NW

15. Polar Projection
Characteristics: a circular map centered on North or South Poles and usually showing one hemisphere at most; meridians are straight lines; parallels are circles
Advantage: Preserves shapes
Disadvantages: scale and area distortion

16. Mercator Projection A type of conformal projection
Characteristics: rectangular; meridians and parallels are both straight lines
Advantage: straight line drawn on map represents a constant compass direction
Disadvantages: scale, area, and distance distortion

17. Goode Projection A type of equal-area projection
Characteristics: odd shape; meridians both straight and curved lines; parallels are straight lines
Advantage: Preserves area
Disadvantage: shape distortion

18. Global Time How many world time zones? US? Not exact…why?
Solar noon: period when Sun appears to be highest in the sky
Lines of longitude used for time zones
15° of longitude = 1 hr of time (360° in one rotation ÷ 24 hrs = 15° per hour)
Example 1: If it is 1 a.m. in Washington D.C., what time is it in Honolulu, Hawaii?
8 p.m
Example 2: If it is Noon in Charlotte, NC, what time is it in Madrid, Spain?
6 p.m.

19. U.S. time zones

20. Time zones

21. Global Time (cont’d) International Date Line
Located approximately along 180°
Why? 180° ÷ 15° per hr = 12 hr. So if it’s 1pm on the Prime Meridian, the IDL is 1am (next day).
West adds a day
East subtract a day
Daylight Savings Time
Midnight Meridian—the meridian that is experiencing midnight (the midnight meridian is NOT stationary)

22. Time Examples
If it is 10 a.m. in Santiago, Chile on Tuesday, May 25, what is the time and date in Taipei, Taiwan?
10 p.m. the same day
If it is 1 p.m. in Juneau, Alaska on Saturday, June 12, what is the time and date in Tokyo, Japan?
7 a.m. the next day (June 13)

23. Longitudnal Time Problems
Example 1: If you depart Washington D.C. (33°N, 77°W) at Noon, at what speed would you have to travel to arrive in Denver, CO (39°N, 105°W) at Noon? Assume travel along the 35°N parallel.
Miles=(69) x (COS 35) x (28°)=1,582 miles
1,582 miles / 2 = 791 mph
Example 2: If you depart Philadelphia, PA (40°N, 75°W) at 1 p.m., at what speed would you have to travel to arrive in Seattle, WA (48°N, 122°W) at 2 p.m.? Assume travel along the 45°N parallel.
Miles=(69) x (COS 45) x (47°)=2,293 miles
2,293 miles / 4 = 573 mph

24. Earth’s Revolution Movement of the Earth around the Sun
Counterclockwise if viewed from above
One revolution = days = 1 yr
Responsible for:
Seasons
Amount of daylight (along with Earth’s tilt)

25. Earth’s Revolution (cont’d)
When viewed from above, notice that path of Earth is not a perfect circle, but an ellipse or oval.
Perihelion:
When Earth is closest to the Sun
Occurs in January (Northern Hemisphere winter)
Aphelion:
When Earth is farthest from the Sun
Occurs in July (Northern Hemisphere summer)

26. Earth’s Revolution

27. Earth’s Revolution (cont’d)
Along with perihelion and aphelion, other times in revolution also have specific names: equinoxes and solstices.

28. Equinoxes March (vernal) and September (autumnal)
Sun’s rays hit equator at 90° (subsolar pt.)
All latitudes receive ~12 hrs of daylight
Circle of illumination from North Pole to South Pole

29. Solstices Occur in June (summer) and December (winter)
Subsolar point in June: Tropic of Cancer (23.5°N); in Dec: Tropic of Capricorn (23.5°S)
June solstice: areas from 66.5°N to North Pole receive 24 hrs of daylight (movie – “Insomnia”)
Winter solstice: areas from 66.5°S to South Pole receive 24 hrs of daylight