Earth Science Using a Globe Lab Name: __________________________ Period: ______________ A. Latitude and Longitude Latitude is distance (in degrees) north or south of the Equator; it is measured by parallels. The latitude of the Equator is 0. The latitudes of the north and south poles are 90N and 90S respectively. The latitude of Phoenix is 33N; it is 33 north of the Equator. Longitude is distance (in degrees) east or west of the Prime Meridian. It is measured by meridians. The Prime Meridian passes through Greenwich, England and its longitude is 0. Exactly halfway around the Earth from the Prime Meridian is the International Date Line; its longitude is 180 (E or W). The longitude of Phoenix is 112W; it is 112 west of the Prime Meridian. Any place on Earth can be located by reading off its latitude and longitude coordinates (in degrees). For more precise locations, each degree of longitude and latitude are divided into 60 equal parts called minutes (symbolized as ‘). Likewise, each minute is divided into 60 equal parts called seconds (symbolized as “). 1. Use a globe to find the name of the place located at each of the following pairs of coordinates: a. 15N, 90W c. 81S, 180 b. 50S, 60W d. 45N, 60E 2. Give the coordinates for each of the following places: a. Honolulu, Hawaii c. Tokyo, Japan b. London, England d. Sydney, Australia B. Magnetic Declination The two natural points for describing location on Earth are the axis of rotation. These points are called the true North and South Poles. They are the points around which the rest of the world rotates. All longitude lines come together at the poles. The North Star (called Polaris) is located directly above the true North Pole. The poles define true directions on Earth. Another point, useful for determining directions on Earth is the Magnetic North Pole. The Magnetic North Pole is the place towards which all compasses point. It is located in the Northwest Territories of Canada near Prince Wales Island. (Find it on your globe). On most maps, a line drawn straight from the bottom to the top would point to true north. This is usually shown by an arrow-pointing north. The map may also show an arrow pointing to magnetic north. The angle between these two directions is called magnetic declination. If you are using a map and a compass, it is important to realize that the compass does not usually point exactly toward true north. Your compass must be set at the appropriate magnetic declination for your location. 3. After reading the above information, write your own definition for: a. True North Pole b. Magnetic North Pole c. Magnetic declination 4. Give the latitude and longitude coordinates of: a. True North Pole b. Magnetic North Pole 5. Locate the following places on the globe. If you were standing in the place, what true direction would a compass be pointing? a. Godhaven, Greenland c. Dallas, Texas b. Point Barrow, Alaska d. The True North Pole C. Great Circles Any circle that cuts the Earth into two equal halves is a great circle. The Equator is a great circle but other parallels are not. The Prime Meridian and the International Date Line together trace out a great circle. So do all other corresponding pairs of meridians. Any line drawn around the largest part of the Earth (no matter what its orientation) is a great circle. Great circles are important for global navigation. The shortest distance between any two places on Earth is traced out by the great circle that would cut the Earth in half along that path. The shortest distance between two points on a flat (distorted) world map is not a straight line. For example, in traveling from Phoenix, Arizona to Cairo, Egypt, it is shorter to go north from Arizona rather than directly east. Find both cities on a flat map and on the globe and compare the distance of the two directions. To find a great circle route between any two places on a globe, simply stretch a string between the two points until it takes the shortest distance. 6. Write your own definition for a great circle. 7. Explain why global navigators want to follow great circle routes. 8. In what direction would you travel to take the following trips by the shortest route? From: a. Arizona b. Brisbane, Australia c. Cairo, Egypt d. Casablanca, Morocco e. Ecuador, South America To: India Paris, France Uruguay, South America Tokyo, Japan Kenya, Africa 9. When should you travel directly east or west to take the shortest route?