CHAPTER 2 SECTION 1 You Are Here - Weebly

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CHAPTER 2 Maps as Models of the Earth

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You Are Here

BEFORE YOU READ

After you read this section, you should be able to answer these questions:

? What is a map? ? What are latitude and longitude? ? How can you find locations on Earth?

What Is a Map?

A map is a model that shows the features of an object. Most maps that people use show the features of Earth's surface. Some maps show all of the Earth's surface. Other maps show only part of it. Maps can show natural features, such as rivers. They can also show features made by people, such as roads.

STUDY TIP

Discuss Read this section quietly to yourself. In a small group, try to figure out anything you didn't understand.

FINDING DIRECTIONS ON EARTH The Earth's shape is similar to a sphere, but the Earth

is not a true sphere. A true sphere has no top, bottom, or sides--it looks the same from all directions. In addition, a true sphere has no reference points. Reference points are certain locations that never change. They can be used to define directions.

Unlike a true sphere, the Earth has two reference points. They are located where the Earth's axis of rotation passes through the Earth's surface. The reference points are called the North Pole and the South Pole. The North and South Poles are known as geographic poles. Since these poles never move, they are used as reference points to define directions on Earth.

READING CHECK

1. Define What are reference points?

The North Pole and the South Pole can be used as reference points to define directions on Earth.

North Pole

South Pole

Earth's axis of rotation

TAKE A LOOK

2. Identify What are two reference points on Earth?

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READING CHECK 3. Identify What are the four cardinal directions?

READING CHECK 4. Describe In which general cardinal direction does a compass needle point?

CARDINAL DIRECTIONS A reference point alone will not help you give good

directions. You also need to describe how to get from one place to another. To do this, you can use the cardinal directions. The cardinal directions are north, south, east, and west. To use cardinal directions properly, you will need to use a compass.

USING A COMPASS TO FIND DIRECTIONS The Earth is like a giant magnet. It has two magnetic

poles, which are located near the geographic poles. You can use the magnetic poles to help you find the cardinal directions.

A compass is a tool that uses the Earth's natural magnetism to show direction. The needle on a compass points to the magnetic pole that is near the geographic North Pole. Therefore, you can use a compass to learn which direction is north.

TRUE NORTH AND MAGNETIC DECLINATION There is a difference between the location of the

geographic North Pole and the magnetic pole. Therefore, a compass needle cannot show you exactly where the geographic North Pole is. When you use a compass, you have to correct for this difference. True north is the direction of the geographic North Pole. The angle between true north and the direction a compass needle points is called magnetic declination.

Magnetic declination

True north

Geographic North Pole

TAKE A LOOK

5. Define What is true

north?

Geographic South Pole

The magnetic and geographic poles are not in the same place. Therefore, compass readings must be corrected to learn the direction of true north.

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USING MAGNETIC DECLINATION

Magnetic declination is measured in degrees east or west of true north. The magnetic declination is different for different points on the Earth's surface. Once you know the declination for your area, you can use a compass to determine the direction of true north. For example, suppose the magnetic declination in your area is 10?W. This means that true north is 10?E of the direction a compass needle points.

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Critical Thinking

6. Apply Concepts The magnetic declination for an area is 8?E. Compared to the direction a compass needle points, in which direction does true north lie?

21? 20? 19? 18? 17? 16?

15? 14?

13? 12? 11?

10?

24?

22? 20? 18? 16? 14?

12?

10?

8?

6?

4? 0? 2?

9?

8? 7? 6? 5? 4? 3? 2? 1?

The lines on this map connect points that have the same magnetic declination.

TAKE A LOOK

7. Read a Map Roughly what is the magnetic declination in the area in which you live?

How Do People Find Specific Locations on Earth?

All of the houses and buildings in your neighborhood have addresses that give their locations. These addresses may include a street name and a number. You can tell someone exactly where you live by giving them your address. In a similar way, you can use latitude and longitude to give an "address" for any place on Earth.

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READING CHECK 8. Define What are parallels?

LATITUDE The equator is a circle halfway between the North

and South Poles. It divides Earth into two hemispheres, or halves--the Northern Hemisphere and the Southern Hemisphere. Lines of latitude, or parallels, are imaginary lines on Earth's surface that are parallel to the equator.

Latitude is the distance north or south from the equator. Latitude is measured in degrees. The equator represents 0? latitude. The North Pole is 90? north latitude and the South Pole is 90? south latitude. North latitudes are in the Northern Hemisphere and south latitudes are in the Southern Hemisphere.

TAKE A LOOK

9. Describe Which parallel is farther from the equator: 10? N latitude or 10? S latitude?

.ORTH0OLE .

%QUATOR

. .

.ORTHERN (EMISPHERE

.

3

3OUTHERN (EMISPHERE

3 3

0ARALLELS

3OUTH0OLE 3

LONGITUDE Lines of longitude, or meridians, are imaginary lines

that link the geographic poles. Lines of longitude are similar to the lines on a basketball. The lines all touch at the poles. They are farthest apart at the equator. The prime meridian is the line that represents 0? longitude. Longitude is the distance east or west of the prime meridian. Like latitude, longitude is measured in degrees.

The prime meridian does not circle the whole globe. It runs from the North Pole, through Greenwich, England, to the South Pole. On the other side of the globe, the 180? meridian runs from the North to the South Pole. Together, the prime meridian and the 180? meridian divide the Earth into Western and Eastern Hemispheres.

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? MERIDIAN

.ORTH 0OLE

%ASTERN

7 7

%(E%MISPHERE

%

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Critical Thinking

10. Apply Concepts A friend asks you what the distance is between 80?E longitude and 90?E longitude. What else do you need to know in order to answer your friend's question? Explain why you need this piece of information.

7ESTERN (EMISPHERE

3OUTH 0OLE

0RIME MERIDIAN

USING LATITUDE AND LONGITUDE Lines of latitude and longitude cross to form a grid. This

grid is shown on maps and globes. You can use the lines of latitude and longitude to tell someone the location of any point on the Earth's surface. First, find the point on a map like the one below. Then, estimate the latitude and longitude of the point, using the lines closest to it.

45?N

40?N

35?N

30?N

25?N

120?W 115?W 110?W 105?W 100?W 95?W 90?W 85?W 80?W 75?W You can use latitude and longitude to locate points on a map. For example, this city is located very close to latitude 35?N, longitude 105?W.

TAKE A LOOK

11. Read a Map Circle the city on the map that is closest to latitude 45?N, longitude 100?W.

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