1. Chapter 1 The Earth as a Rotating Planet
Visualizing Physical Geography by Alan Strahler and Zeeya Merali
Chapter 1 The Earth as a Rotating Planet
Visualizing Physical Geography Copyright © 2008 John Wiley and Sons Publishers Inc.

2. Chapter Overview—Also Visual summary
The Shape of the Earth
The Earth’s Rotation
The Geographic Grid
Map Projections
Global Time
The Earth’s Revolution Around the Sun
Visualizing Physical Geography Copyright © 2008 John Wiley and Sons Publishers Inc.

3. Key Chapter Objectives
Define the axis and poles.
Examine the method we use to determine position on the globe.
Explain map projections and their differences.
Visualizing Physical Geography Copyright © 2008 John Wiley and Sons Publishers Inc.

4. Key Chapter Objectives
Describe how the sun’s position regulates time, the need for world time zones and the use of daylight savings time.
Explain and illustrate how the seasons are created, focusing on seasonal variation.
Visualizing Physical Geography Copyright © 2008 John Wiley and Sons Publishers Inc.

5. The Shape of the Earth The Earth is round
Looks flat from earth
Space views
Visualizing Physical Geography Copyright © 2008 John Wiley and Sons Publishers Inc.

6. The Earth is not a perfect sphere
The Shape of the Earth
The Earth is not a perfect sphere
Equatorial diameter slightly greater than polar diameter
Earth is an oblate ellipsoid–slightly flattened
The geoid exaggerates small departures from spherical
Geoid- based on the pull of gravity.
Visualizing Physical Geography Copyright © 2008 John Wiley and Sons Publishers Inc.

7. Earth rotates on its axis: Counterclockwise at North Pole
The Earth’s Rotation
Earth rotates on its axis:
Counterclockwise at North Pole
Left to right (eastward) at Equator
One rotation is a solar day (24 hours)
Axis: an imaginary straight line through the center of the Earth around which the Earth rotates
Poles: the two points on the Earth’s surface where the axis of rotation emerges
Visualizing Physical Geography Copyright © 2008 John Wiley and Sons Publishers Inc.

8. Environmental Effects of the Earth’s Rotation: Day and night
Fluctuating air temperature
Coriolis Effect
Tides
Day and night regulates us- 24 hours
Air temp- energy budget
What coriolis is and ocean currents, wind effect
Tidal action- position and gravitation pull to the moon and earth.
Visualizing Physical Geography Copyright © 2008 John Wiley and Sons Publishers Inc.

9. The Geographic Grid
Parallels and Meridians Geographic grid: network of parallels and meridians used to fix location on the Earth
Parallel: east-west circle on the Earth’s surface, lying on a plane parallel to the equator
Meridian: north-south line on the Earth’s surface, connecting the poles
Visualizing Physical Geography Copyright © 2008 John Wiley and Sons Publishers Inc.

10. The Geographic Grid
Parallels and Meridians Equator: Parallel of latitude lying midway between the Earth’s poles; it is designated latitude 0º
Longest parallel of latitude
Midway between poles
Fundamental reference line for measuring position
Longitude: arc of a parallel between the prime meridian and a given point on the globe
Latitude: arc of a meridian between the equator and a given point on the globe
Visualizing Physical Geography Copyright © 2008 John Wiley and Sons Publishers Inc.

11. The Geographic Grid
Latitude and Longitude Latitude is measured north and south of the equator, up to 90º
Longitude is measured east and west of the Prime Meridian—meridian that passes through Greenwich, England—up to 180º
Visualizing Physical Geography Copyright © 2008 John Wiley and Sons Publishers Inc.

12. Many types of maps, for many different purposes
Map Projections
Many types of maps, for many different purposes
Visualizing Physical Geography Copyright © 2008 John Wiley and Sons Publishers Inc.

13. Map Projections Map Scale
1:50,000
1 unit of map distance=50,000 units of distance on the Earth
Map Scale
Scale fraction: a ratio that tells how to convert distance on the map to true distance on the Earth
Visualizing Physical Geography Copyright © 2008 John Wiley and Sons Publishers Inc.

14. View map projections in Student resources Wiley Plus
Map projection: a system of parallels and meridians representing the Earth’s curved surface drawn on a flat surface
Curved surface cannot be projected onto a flat sheet without distortion
Each map projection has a specific purpose
Each projection has advantages and drawbacks
View map projections in
Student resources Wiley Plus
Visualizing Physical Geography Copyright © 2008 John Wiley and Sons Publishers Inc.

15. Map Projections
Mercator projection: map projection with horizontal parallels and vertical meridians
Used for navigation-sailors
Scale increases from equator to poles for parallels—spaces differs- higher latitude (above 60 degrees is double than at the equator. Needs to be cut off at 80 and enlarges features at the poles.
Straight line features- Use maps of temperatures, winds, and pressures
Straight line on a Mercator projection not the shortest distance between two points

16. Map Projections
Goode Projection: Equal-area map projection often used to display information such as climate or soil type
Shows true sizes of regions on Earth’s surface
Distorts shapes of places, especially high latitudes and at edges of map
Visualizing Physical Geography Copyright © 2008 John Wiley and Sons Publishers Inc.

17. Map Projections
Polar projection: map projection centered on Earth’s North or South Pole
Used for maps of polar regions
Scale increases outward
Shows only one hemisphere
Use in weather maps
Visualizing Physical Geography Copyright © 2008 John Wiley and Sons Publishers Inc.

18. Global Time
Standard Time: time system based on the local time of a standard meridian and applied to belts of longitude extending roughly 7 ½ º on either side of the meridian
Time zones: zones or belts within which standard time is applied
Visualizing Physical Geography Copyright © 2008 John Wiley and Sons Publishers Inc.

19. Global Time World Time Zones
Visualizing Physical Geography Copyright © 2008 John Wiley and Sons Publishers Inc.

20. International Date Line
Global Time
International Date Line
180th meridian
Moving west across the date line: advance calendar one day
Moving east across date line: set calendar back one day
No change in clock time when crossing date line
Visualizing Physical Geography Copyright © 2008 John Wiley and Sons Publishers Inc.

21. Daylight Saving Time: clocks set ahead one hour
Global Time
Daylight Saving Time: clocks set ahead one hour
Not observed in all locations
Visualizing Physical Geography Copyright © 2008 John Wiley and Sons Publishers Inc.

22. Earth’s Revolution Around the Sun
Earth revolves around the sun every days
Orbit is an ellipse
Leap year corrects for the extra quarter day
Orbit is counterclockwise
Perihelion: point in orbit when Earth is closest to Sun
Aphelion: point in orbit when Earth is farthest from Sun
Visualizing Physical Geography Copyright © 2008 John Wiley and Sons Publishers Inc.

23. Earth’s Revolution Around the Sun
Tilt of the Earth’s Axis Earth has seasons because of the tilt of the axis.
Axis aims toward Polaris (North Star)
Axis tilted at an angle of 23 ½ ° from a right angle to plane of the ecliptic
Plane of the Ecliptic: plane of the Earth’s orbit around the Sun
Visualizing Physical Geography Copyright © 2008 John Wiley and Sons Publishers Inc.

24. Earth’s Revolution Around the Sun
The Four Seasons Earth’s axis tilted toward North Star throughout Earth’s orbit.
December 22: N hemisphere tilted away from the sun at the maximum angle
June 21: N hemisphere tilted toward the sun at the maximum angle
Subsolar point- Single point on earth’s surface sun directly overhead.
View Angle of Sun in the Sky in Wiley Plus
Visualizing Physical Geography Copyright © 2008 John Wiley and Sons Publishers Inc.

25. Earth’s Revolution Around the Sun The Four Seasons
Circle of illumination: separates day hemisphere from night hemisphere
Equinox: time when subsolar point falls on equator and circle of illumination passes through both poles
Winter solstice: solstice occurring on December 21 or 22, when the subsolar point is at 23 1/2° S; December Solstice
Summer solstice: solstice occurring on June 21 or 22, when the subsolar point is at 23 1/2° N; June Solstice
Visualizing Physical Geography Copyright © 2008 John Wiley and Sons Publishers Inc.

26. Earth’s Revolution Around the Sun
Equinox Conditions
Circle of illumination passes through both poles
Subsolar point at equator
Day and night of equal length everywhere on the globe
Occurs twice per year
Vernal Equinox: March 21
Autumnal Equinox: September 23
Subsolar point: point on the Earth’s surface where the sun is directly overhead at noon
Visualizing Physical Geography Copyright © 2008 John Wiley and Sons Publishers Inc.

27. Earth’s Revolution Around the Sun Solstice Conditions
Circle of illumination grazes Arctic and Antarctic Circles
June Solstice: north pole has 24 hours of daylight; daylength increases from equator to north pole
December Solstice: south pole has 24 hours of daylight; daylength increases from equator to south pole
Visualizing Physical Geography Copyright © 2008 John Wiley and Sons Publishers Inc.

28. Discussion Pair/Share
Answer the following questions yourself. Pair up and discuss. Share with class.
How have ecosystems in your city been affected by human activity? Good or bad.
How have various kinds of pollution affected your life? List some sources of pollution in your city.
What do you consider the most important pollution threat to the Earth.
What are 3 things people could do to improve the quality of earth systems.