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

Visualizing Physical Geography Copyright © 2008 John Wiley and Sons Publishers Inc. Chapter Overview The Shape of the Earth The Earth’s Rotation The Geographic Grid Map Projections Global Time

Visualizing Physical Geography Copyright © 2008 John Wiley and Sons Publishers Inc. The Shape of the Earth The Earth is round

Visualizing Physical Geography Copyright © 2008 John Wiley and Sons Publishers Inc. 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

Visualizing Physical Geography Copyright © 2008 John Wiley and Sons Publishers Inc. 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. The Earth’s Rotation Environmental Effects of the Earth’s Rotation: Day and night Fluctuating air temperature Coriolis Effect Tides

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 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

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 180 º

Visualizing Physical Geography Copyright © 2008 John Wiley and Sons Publishers Inc. 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 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

Visualizing Physical Geography Copyright © 2008 John Wiley and Sons Publishers Inc. Map Projections 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

Visualizing Physical Geography Copyright © 2008 John Wiley and Sons Publishers Inc. Map Projections Mercator projection: map projection with horizontal parallels and vertical meridians Invented 1569 by Gerardus Mercator Used for navigation Scale increases from equator to poles Straight line on the map is a line of constant compass bearing Straight line on a Mercator projection not the shortest distance between two points

Visualizing Physical Geography Copyright © 2008 John Wiley and Sons Publishers Inc. 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

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. Global Time International Date Line 180 th 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. Global Time Daylight Saving Time: clocks set ahead one hour Not observed in all locations