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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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

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.

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.

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.

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

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.

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.

Earth’s Revolution Around the Sun Earth revolves around the sun every 365.242 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.

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.

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.

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.

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.

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.

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.