physical geography chap1lec1

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physical geography chap1lec1

  1. 1. Chapter 1 The Earth as a Rotating Planet Visualizing Physical Geography Copyright © 2008 John Wiley and Sons Publishers Inc. Visualizing Physical Geography by Alan Strahler and Zeeya Merali
  2. 2. Visualizing Physical Geography Copyright © 2008 John Wiley and Sons Publishers Inc. <ul><li>Chapter Overview </li></ul><ul><li>The Shape of the Earth </li></ul><ul><li>The Earth’s Rotation </li></ul><ul><li>The Geographic Grid </li></ul><ul><li>Map Projections </li></ul><ul><li>Global Time </li></ul><ul><li>The Earth’s Revolution Around the Sun </li></ul>
  3. 3. Visualizing Physical Geography Copyright © 2008 John Wiley and Sons Publishers Inc. The Shape of the Earth The Earth is round
  4. 4. Visualizing Physical Geography Copyright © 2008 John Wiley and Sons Publishers Inc. The Shape of the Earth <ul><li>The Earth is not a perfect sphere </li></ul><ul><li>Equatorial diameter slightly greater than polar diameter </li></ul><ul><li>Earth is an oblate ellipsoid– slightly flattened </li></ul><ul><li>The geoid exaggerates small departures from spherical </li></ul>
  5. 5. Visualizing Physical Geography Copyright © 2008 John Wiley and Sons Publishers Inc. The Earth’s Rotation <ul><li>Earth rotates on its axis: </li></ul><ul><li>Counterclockwise at North Pole </li></ul><ul><li>Left to right (eastward) at Equator </li></ul><ul><li>One rotation is a solar day (24 hours) </li></ul>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
  6. 6. Visualizing Physical Geography Copyright © 2008 John Wiley and Sons Publishers Inc. The Earth’s Rotation <ul><li>Environmental Effects of the Earth’s Rotation: </li></ul><ul><li>Day and night </li></ul><ul><li>Fluctuating air temperature </li></ul><ul><li>Coriolis Effect </li></ul><ul><li>Tides </li></ul>
  7. 7. Visualizing Physical Geography Copyright © 2008 John Wiley and Sons Publishers Inc. 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
  8. 8. Visualizing Physical Geography Copyright © 2008 John Wiley and Sons Publishers Inc. The Geographic Grid <ul><li>Parallels and Meridians Equator : Parallel of latitude lying midway between the Earth’s poles; it is designated latitude 0 º </li></ul><ul><li>Longest parallel of latitude </li></ul><ul><li>Midway between poles </li></ul><ul><li>Fundamental reference line for measuring position </li></ul>Latitude : arc of a meridian between the equator and a given point on the globe Longitude : arc of a parallel between the prime meridian and a given point on the globe
  9. 9. Visualizing Physical Geography Copyright © 2008 John Wiley and Sons Publishers Inc.
  10. 10. Visualizing Physical Geography Copyright © 2008 John Wiley and Sons Publishers Inc. The Geographic Grid Latitude and Longitude Latitude is measured north and south of the equator, up to 90 º Longitude is measured east and west of the Prime Meridian—meridian that passes through Greenwich, England — up to 180 º
  11. 11. Visualizing Physical Geography Copyright © 2008 John Wiley and Sons Publishers Inc.
  12. 12. Visualizing Physical Geography Copyright © 2008 John Wiley and Sons Publishers Inc.
  13. 13. Visualizing Physical Geography Copyright © 2008 John Wiley and Sons Publishers Inc.
  14. 14. Visualizing Physical Geography Copyright © 2008 John Wiley and Sons Publishers Inc.
  15. 15. Visualizing Physical Geography Copyright © 2008 John Wiley and Sons Publishers Inc.
  16. 16. Visualizing Physical Geography Copyright © 2008 John Wiley and Sons Publishers Inc. Map Projections Many types of maps, for many different purposes
  17. 17. Visualizing Physical Geography Copyright © 2008 John Wiley and Sons Publishers Inc. Map Projections Map Scale Scale fraction: a ratio that tells how to convert distance on the map to true distance on the Earth 1:50,000 1 unit of map distance=50,000 units of distance on the Earth
  18. 18. Visualizing Physical Geography Copyright © 2008 John Wiley and Sons Publishers Inc. Map Projections <ul><li>Map projection : a system of parallels and meridians representing the Earth’s curved surface drawn on a flat surface </li></ul><ul><li>Curved surface cannot be projected onto a flat sheet without distortion </li></ul><ul><li>Each map projection has a specific purpose </li></ul><ul><li>Each projection has advantages and drawbacks </li></ul>
  19. 19. Visualizing Physical Geography Copyright © 2008 John Wiley and Sons Publishers Inc. Map Projections <ul><li>Mercator projection : map projection with horizontal parallels and vertical meridians </li></ul><ul><li>Invented 1569 by Gerardus Mercator </li></ul><ul><li>Used for navigation </li></ul><ul><li>Scale increases from equator to poles </li></ul><ul><li>Straight line on the map is a line of constant compass bearing </li></ul><ul><li>Straight line on a Mercator projection not the shortest distance between two points </li></ul>
  20. 20. Visualizing Physical Geography Copyright © 2008 John Wiley and Sons Publishers Inc. Map Projections <ul><li>Goode Projection : Equal-area map projection often used to display information such as climate or soil type </li></ul><ul><li>Shows true sizes of regions on Earth’s surface </li></ul><ul><li>Distorts shapes of places, especially high latitudes and at edges of map </li></ul>
  21. 21. Visualizing Physical Geography Copyright © 2008 John Wiley and Sons Publishers Inc. Map Projections <ul><li>Polar projection : map projection centered on Earth’s North or South Pole </li></ul><ul><li>Used for maps of polar regions </li></ul><ul><li>Scale increases outward </li></ul><ul><li>Shows only one hemisphere </li></ul>
  22. 22. Visualizing Physical Geography Copyright © 2008 John Wiley and Sons Publishers Inc. 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
  23. 23. Visualizing Physical Geography Copyright © 2008 John Wiley and Sons Publishers Inc. Global Time World Time Zones
  24. 24. Visualizing Physical Geography Copyright © 2008 John Wiley and Sons Publishers Inc. Global Time <ul><li>International Date Line </li></ul><ul><li>180 th meridian </li></ul><ul><li>Moving west across the date line: advance calendar one day </li></ul><ul><li>Moving east across date line: set calendar back one day </li></ul><ul><li>No change in clock time when crossing date line </li></ul>
  25. 25. Visualizing Physical Geography Copyright © 2008 John Wiley and Sons Publishers Inc. Global Time Daylight Saving Time: clocks set ahead one hour Not observed in all locations
  26. 26. Visualizing Physical Geography Copyright © 2008 John Wiley and Sons Publishers Inc. Earth’s Revolution Around the Sun <ul><li>Earth revolves around the sun every 365.242 days </li></ul><ul><li>Orbit is an ellipse </li></ul><ul><li>Leap year corrects for the extra quarter day </li></ul><ul><li>Orbit is counterclockwise </li></ul><ul><li>Perihelion : point in orbit when Earth is closest to Sun </li></ul><ul><li>Aphelion : point in orbit when Earth is farthest from Sun </li></ul>
  27. 27. Visualizing Physical Geography Copyright © 2008 John Wiley and Sons Publishers Inc. Earth’s Revolution Around the Sun <ul><li>Tilt of the Earth’s Axis Earth has seasons because of the tilt of the axis. </li></ul><ul><li>Axis aims toward Polaris (North Star) </li></ul><ul><li>Axis tilted at an angle of 23 ½ ° from a right angle to plane of the ecliptic </li></ul>Plane of the Ecliptic : plane of the Earth’s orbit around the Sun
  28. 28. Visualizing Physical Geography Copyright © 2008 John Wiley and Sons Publishers Inc. Earth’s Revolution Around the Sun <ul><li>The Four Seasons Earth’s axis tilted toward North Star throughout Earth’s orbit. </li></ul><ul><li>December 22: N hemisphere tilted away from the sun at the maximum angle </li></ul><ul><li>June 21: N hemisphere tilted toward the sun at the maximum angle </li></ul>
  29. 29. Visualizing Physical Geography Copyright © 2008 John Wiley and Sons Publishers Inc. Earth’s Revolution Around the Sun The Four Seasons Summer solstice : solstice occurring on June 21 or 22, when the subsolar point is at 23 1/2 ° N; June Solstice Winter solstice : solstice occurring on December 21 or 22, when the subsolar point is at 23 1/2 ° S; December Solstice Equinox : time when subsolar point falls on equator and circle of illumination passes through both poles Circle of illumination : separates day hemisphere from night hemisphere
  30. 30. Visualizing Physical Geography Copyright © 2008 John Wiley and Sons Publishers Inc. Earth’s Revolution Around the Sun Equinox Conditions Subsolar point : point on the Earth’s surface where the sun is directly overhead at noon <ul><li>Circle of illumination passes through both poles </li></ul><ul><li>Subsolar point at equator </li></ul><ul><li>Day and night of equal length everywhere on the globe </li></ul><ul><li>Occurs twice per year </li></ul><ul><ul><li>Vernal Equinox: March 21 </li></ul></ul><ul><ul><li>Autumnal Equinox: September 23 </li></ul></ul>
  31. 31. Visualizing Physical Geography Copyright © 2008 John Wiley and Sons Publishers Inc. Earth’s Revolution Around the Sun <ul><li>Solstice Conditions </li></ul><ul><li>Circle of illumination grazes Arctic and Antarctic Circles </li></ul><ul><li>June Solstice: north pole has 24 hours of daylight; daylength increases from equator to north pole </li></ul><ul><li>December Solstice: south pole has 24 hours of daylight; daylength increases from equator to south pole </li></ul>

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