chapter 2: mapping our world

To find out more aboutmaps, visit the EarthScience Web Site at earthgeu.com

26

What You’ll Learn• How latitude and longi-

tude are used to locateplaces on Earth.

• How maps are made,and what types ofmaps are best suited toparticular purposes.

• What technology is used to map Earth from space.

Why It’s ImportantMaps help us to locateexact places on Earth.All forms of transporta-tion, including ships,planes, cars, and trucks,rely on accurate maps for guidance.

MappingOurWorld

MappingOurWorld

22

http://earthgeu.com

2.1 Latitude and Longitude 27

Have you ever been asked fordirections? If so, you know that it’simportant to include as much detailas possible so that the person askingfor directions will not get lost. Youalso may have realized that it helps to draw a detailed map of the desti-nation in question.

1. Give verbal directions from yourschool to your home to a classmatewho does not know where you live.Include as much detail as possiblein your description.

2. Use a sheet of graph paper and col-ored pencils to draw a map fromyour school to your home. Includelandmarks and other details. Sharethis map with your classmate.

3. Have your classmate also give you a description of where his or herhome is located in relation to yourschool. Your classmate should thendraw a map to his or her home foryou to examine.

Observe Which didyou find more helpful,the verbal directions orthe map? Explain youranswer. What kind ofinformation did youinclude in your map?With your classmate,discuss how you couldimprove your maps.What details would you add?

Make and Use a MapDiscovery LabDiscovery Lab

OBJECTIVES

• Compare and contrastlatitude and longitude.

• Describe how time zones vary.

VOCABULARY

cartographyequatorlatitudelongitudeprime meridianInternational Date Line

For thousands of years people have used maps such as the oneshown at left to define borders and to find places. We still rely onmaps for a variety of purposes. The science of mapmaking is calledcartography. Cartographers use an imaginary grid of parallel linesand vertical lines to locate points on Earth exactly. In this grid, theequator circles Earth halfway between the north and south poles.The equator separates Earth into two equal halves called the north-ern hemisphere and the southern hemisphere.

LATITUDELines running parallel to the equator are called lines of latitude.Latitude is the distance in degrees north or south of the equator. Theequator, which serves as the reference point for latitude, is numbered0° latitude. The poles are each numbered 90° latitude. Latitude isthus measured from 0° at the equator to 90° at the poles. Locations

Latitude and Longitude2.12.1

Figure 2-1 Lines of latitudeare parallel to the equator(A). The value in degrees of each line of latitude isdetermined by measuringthe imaginary angle createdbetween the equator, thecenter of Earth, and the lineof latitude (B).

north of the equator are referred to by degrees north latitude (N).Locations south of the equator are referred to by degrees south lati-tude (S). For example, Syracuse, New York, is located at 43° north latitude, and Christchurch, New Zealand, is located at 43° south latitude. Lines of latitude are illustrated in Figure 2-1.

Degrees of Latitude Each degree of latitude is equivalent toabout 111 km on Earth’s surface. How did cartographers determinethis distance? Earth is a sphere, and can be divided into 360 degrees.The circumference of Earth is about 40 000 km. To find the distanceof each degree of latitude, cartographers divide 40 000 km by 360°.To locate positions on Earth more precisely, cartographers breakdown degrees of latitude into 60 smaller units, called minutes. Thesymbol for a minute is ′. The actual distance on Earth’s surface ofeach minute of latitude is 1.85 km, which is obtained by dividing 111km by 60′. A minute of latitude can be further divided into seconds,which are represented by the symbol ″. Longitude, which is discussednext, is also divided into degrees, minutes, and seconds.

28 CHAPTER 2 Mapping Our World

90° N

0°

Latitudesnorthof 0°

Latitude(equator)

Latitudessouthof 0°

90° S

90° N

Equator

Earth’scenter

Angle of latitude

90° S

Using Numbers Yourplane has flown from30° north latitude to42° north latitude.Approximately howmany kilometershave you traveled?

Equator Equator

Longitude°W

Longitude°E

Primemeridian 0°

Line oflongitude

Primemeridian 0°Figure 2-2 The reference

line for longitude is theprime meridian (A). Thedegree value of each line oflongitude is determined bymeasuring the imaginaryangle created between theprime meridian, the centerof Earth, and the line oflongitude (B).

A B

A B

LONGITUDETo locate positions in east and west direc-tions, cartographers use lines of longitude,also known as meridians. As shown in Figure2-2, longitude is the distance in degrees eastor west of the prime meridian, which is thereference point for longitude. The primemeridian represents 0° longitude. In 1884,astronomers decided that the prime merid-ian should go through Greenwich, England,home of the Royal Naval Observatory. Pointswest of the prime meridian are numberedfrom 0° to 180° west longitude (W); pointseast of the prime meridian are numberedfrom 0° to 180° east longitude (E).

Semicircles Unlike lines of latitude, linesof longitude are not parallel. Instead, theyare large semicircles that extend verticallyfrom pole to pole. For instance, the primemeridian runs from the north pole throughGreenwich, England, to the south pole. Theline of longitude on the opposite side ofEarth from the prime meridian is the 180°meridian. There, east lines of longitudemeet west lines of longitude. This meridianis also known as the International DateLine, as you’ll learn later in this section.

Degrees of Longitude Degrees of lati-tude cover relatively consistent distances.The distances covered by degrees of longi-tude, however, vary with location. Referback to Figure 2-2. As you can see, lines oflongitude converge at the poles into a point.Thus, one degree of longitude varies fromabout 111 km at the equator to essentiallythe distance covered by a point at the poles.

Locating Places with CoordinatesBoth latitude and longitude are needed toprecisely locate positions on Earth, as you’llsee in the MiniLab on this page. For example,it is not sufficient to say that New Orleans,


How can you locate places on Earth?

Determine latitude and longitude for specific places.

Procedure1. Use a world map or globe to locate the

prime meridian and the equator.2. Take a few moments to become familiar

with the grid system. Examine lines of latitude and longitude on the map or globe.

Analyze and Conclude1. Use a map to find the latitude and

longitude of the following places.Mount St. Helens, WashingtonNiagara Falls, New YorkMt. Everest, NepalGreat Barrier Reef, Australia

2. Use the map to find the name of theplaces with the following coordinates.0°03’S, 90°30’W27°07’S, 109°22’W41°10’N, 112°30’W35°02’N, 111°02’W3°04’S, 37°22’E

3. Find the latitude and longitude of yourhometown, the nearest national or statepark, and your state capital.

Louisiana, is located at 29°57′ north latitude becausethat measurement includes any place on Earth locatedalong the 29°57′ line of north latitude. The same is trueof the longitude of New Orleans—90°04′ west longi-tude could be any point along that longitude from poleto pole. To precisely locate New Orleans, we use itscomplete coordinates, latitude and longitude, as shownin Figure 2-3. Note that latitude comes first in refer-ence to the coordinates of a particular location.

TIME ZONESAs Figure 2-4 shows, Earth is divided into 24 timezones. Why 24? Earth takes about 24 hours to rotateonce on its axis. Thus, there are 24 times zones, eachrepresenting a different hour. Because Earth is con-

stantly spinning, time is always changing. Each time zone is 15° wide,corresponding roughly to lines of longitude. For convenience’s sake,however, time zone boundaries have been adjusted in local areas. Forexample, if a city were split by a time zone, confusion would result.In such a situation, the time zone boundary is moved outside of thecity. Large countries, however, often have several times zones. Thereare six different time zones in the United States, as shown in Figure2-5. When it’s 10 A.M. in Atlanta, Georgia, it’s 7 A.M. in Los Angeles,California. What time is it in Chicago, Illinois?


30°

40°

90°110°130°

150°

70°50°

30°

20°

10°

0°

10°

20°

50°

Figure 2-4 Earth is dividedinto 24 time zones. Eachzone represents a differenthour.

Half-hourzones

No zonesystemadopted

UnitedStates

Brazil

Africa

Europe

Asia

Australia

Phillipines

Madagascar

Iceland

BritishIsles

Argentina

HawaiianIslands

Canada

Prim

e M

erid

ian

Inte

rnat

ion

al D

ate

Lin

e

Greenland

11P.M.

12A.M.

1A.M.

2A.M.

3A.M.

4A.M.

5A.M.

6A.M.

7A.M.

8A.M.

9A.M.

10A.M.

11A.M.

12P.M.

1P.M.

2P.M.

3P.M.

4P.M.

5P.M.

6P.M.

7P.M.

8P.M.

9P.M.

10P.M.

+11 +12 –11 –10 –9 –8 –7 –6 –5 –4 –3 –2 –1 0 +1 +2 +3 +4 +5 +6 +7 +8 +9 +10

International Time Zones

Figure 2-3 The preciselocation of New Orleans is29°57′N, 90°04′W.

Source: Time Almanac 2001

Calendar Dates Each day ends and the next day begins at thestroke of midnight. Every time zone experiences this transition fromone day to the next, with the calendar advancing to the next day atmidnight. Each time you travel through a time zone, you gain or losetime until, at some point, you gain or lose an entire day. TheInternational Date Line, or 180° meridian, serves as the transitionline for calendar days. If you were traveling west across theInternational Date Line, you would advance your calendar one day. Ifyou were traveling east, you would move your calendar back one day.


1. What is cartography?

2. Compare and contrast latitude and longi-tude. What is the reference point for linesof latitude? What is the reference pointfor lines of longitude?

3. What is the International Date Line? If itis 3 P.M. on Thursday, July 4, in Salt LakeCity, Utah, what time and day is it inTokyo, Japan? Use Figure 2-4 for help.

4. Estimate the time difference betweenyour home and places that are 60° eastand west longitude of your home.

5. Critical Thinking If you were flying directlysouth from the north pole and reached 70°north latitude, how many more degrees oflatitude would be left to pass over beforeyou reached the south pole?

SKILL REVIEW

6. Comparing and Contrasting Describe howthe distance of a degree of longitudevaries from the equator to the poles. Formore help, refer to the Skill Handbook.

Figure 2-5 Large countriessuch as the United Statesare often split into multipletime zones. The UnitedStates has six time zones,including Alaska andHawaii.

12

6

111210

39

4857

12

6

111210

39

4857

12

6

111210

39

4857

12

6

111210

39

4857

12

6

111210

39

4857

12

6

111210

39

4857

PacificAlaska

Standard Time

Hawaii-AleutianStandard Time

Mountain Central Eastern

MI

IN OHIL

WIMN

IA

MO

AR

LAMS

TN

KYNC

SCGA

FL

VAWV

PA

NY

NJDE

MD

MA

VTNH

MEND

SD

NE

KS

OK

TX

NM

CO

WY

MT

ID

UT

AZ

NV

OR

WAAK

HI

CA

RICT

AL

U.S. Time Zones

earthgeu.com/self_check_quiz

http://earthgeu.com/self_check_quiz

2.22.2 Types of Maps

Maps are flat models of a three-dimensional object, Earth. BecauseEarth is curved, it’s difficult to represent on a piece of paper. Thus, allflat maps distort to some degree either the shapes or the areas oflandmasses. Cartographers use projections to make maps. A mapprojection is made by transferring points and lines on a globe’s sur-face onto a sheet of paper. You’ll use a projection of a world map inthe Science & Math feature at the end of this chapter.

MERCATOR PROJECTIONSA Mercator projection is a map that has parallel lines of latitude andlongitude. Recall that lines of longitude meet at the poles. When linesof longitude are projected as being parallel on a map, landmassesnear the poles are exaggerated. Thus, in a Mercator projection, theshapes of the landmasses are correct, but their areas are distorted. Asshown in Figure 2-6, Greenland appears much larger than Australia.In reality, Greenland is much smaller than Australia. BecauseMercator projections show the correct shapes of landmasses and alsoclearly indicate direction in straight lines, they are used for the navi-gation of planes and ships.

CONIC PROJECTIONSA conic projection is made by projecting points and lines from aglobe onto a cone, as shown in Figure 2-7. The cone touches theglobe at a particular line of latitude. There is very little distortion inthe areas or shapes of landmasses that fall along this line of latitude.Distortion is evident, however, near the top and bottom of the pro-jection. Because conic projections have a high degree of accuracy forlimited areas, they are excellent for mapping small areas. Hence, theyare used to make road maps and weather maps.

OBJECTIVES

• Compare and contrastdifferent map projections.

• Analyze topographicmaps.

• Describe map character-istics, such as map scalesand map legends.

VOCABULARY

Mercator projectionconic projectiongnomonic projectiontopographic mapcontour linecontour intervalmap legendmap scale


Figure 2-6 In a Mercatorprojection, points and lineson a globe are transferredonto a cylinder-shapedpaper. Mercator projectionsshow true direction but dis-tort areas near the poles.

GNOMONIC PROJECTIONSA gnomonic projection is made by projecting points and linesfrom a globe onto a piece of paper that touches the globe at asingle point. As shown in Figure 2-8, gnomonic projectionsdistort direction and distance between landmasses. However,they are useful in plotting long-distance trips by air and by sea.To understand why, you must understand the concept of agreat circle. Great circles are imaginary lines that divide Earthinto two equal halves. The equator is a great circle, as are anytwo lines of longitude that connect at the poles to form a com-plete circle. On a sphere such as Earth, the shortest distancebetween two points lies along a great circle. Navigators connectpoints on gnomonic projections to plot great-circle routes.

TOPOGRAPHIC MAPSDetailed maps showing the hills and valleys of an area arecalled topographic maps. Topographic maps show changes inelevation of Earth’s surface. They also show mountains, rivers,forests, and bridges, among other features. Topographic mapsuse lines, symbols, and colors to represent changes in elevationand features on Earth’s surface.

Contour Lines Elevation on a topographic map is represented bya contour line. A contour line connects points of equal elevation.Elevation refers to the distance of a location above or below sea level.Because contour lines connect points of equal elevation, they nevercross. If they did, it would mean that the point where they crossedhad two different elevations, which would be impossible.

2.2 Types of Maps 33

Figure 2-8 In a gnomonicprojection, points and linesfrom a globe are projectedonto paper that touchesthe globe at a single point.

Figure 2-7 In a conic pro-jection, points and lines ona globe are projected ontoa cone-shaped paper. Alongthe line of latitude touchedby the paper, there is littledistortion.

Contour Intervals As Figure 2-9 shows, topographic maps usecontour lines to show changes in elevation. The difference in elevationbetween two side-by-side contour lines is called the contour interval.The contour interval is dependent on the terrain. For mountains,the contour lines might be very close together, and the contourinterval might be as great as 100 m. This would indicate that theland is quite steep because there is a large change in elevationbetween lines. You’ll learn more about topographic maps in theProblem-Solving Lab on the next page and in the Mapping GeoLab atthe end of this chapter.

Index Contours To aid in the interpretation of topographic maps,some contour lines are marked by numbers representing their eleva-tions. These are index contours, and they are used hand-in-hand with

contour intervals. If a contour interval on a map is 5 m,you can determine the elevations represented by otherlines around the index contour by adding or subtracting 5 m from the elevation indicated on the index contour.

Depression Contour Lines The elevations of somefeatures such as volcanic craters and mines are lowerthan that of the surrounding landscape. Depressioncontour lines are used to represent such features. On amap, depression contour lines have hachures, or shortlines at right angles to the contour line, to indicatedepressions. The hachures point toward lower eleva-tions, as shown in Figure 2-10.


640

700

Figure 2-9 Points of elevation onEarth’s surface are projected ontopaper to make a topographic map.

Figure 2-10 The depressioncontour lines shown hereindicate that the center ofthe area has a lower eleva-tion than the outer portionof the area.

MAP LEGENDSTopographic maps and most other maps include both human-madeand natural features that are located on Earth’s surface. These fea-tures are represented by symbols, such as black dotted lines for trails,solid red lines for highways, and small black squares and rectanglesfor buildings. A map legend, such as the one shown in Figure 2-11,explains what the symbols represent. For more information aboutthe symbols in map legends, see Appendix D.

MAP SCALESWhen using a map, you need to know how to measure distances. Thisis accomplished by using a map scale. A map scale is the ratiobetween distances on a map and actual distances on the surface ofEarth. There are three types of map scales: verbal scales, graphicscales, and fractional scales. A verbal scale expresses distance as astatement, such as “One centimeter is equal to one kilometer.” Thismeans that one centimeter on the map represents one kilometer onEarth’s surface. A graphic scale consists of a line that represents a cer-tain distance, such as 5 km or 5 miles. The line is broken down intosections, with each section representing a distance on Earth’s surface.For instance, a graphic scale of 5 km may be broken down into fivesections, with each section representing 1 km.

2.2 Types of Maps 35

BM 283

Highway

Trail

Bridge

Railroad

Buildings

School, church

Spot elevation

Contour line

Depressioncontour lines(hachures)

Stream

Marsh

Analyze changes in elevationGradient refers to the steepness of a slope.To measure gradient, divide the change inelevation between two points on a map bythe distance between the points. Use the map to answer the questions; convert your answers to SI.

Analysis1. Use the map scale and a ruler to deter-

mine the distance from point A to pointB. Record the change in elevationbetween the two points.

2. If you were to hike this distance, whatwould be the gradient of your climb?

Thinking Critically3. Calculate the gradient from point B to

point C. Would it be more difficult tohike from point A to point B, or frompoint B to point C? Explain.

4. Between point A and point C, where isthe steepest part of the hike? How doyou know?

Calculating Gradients

Figure 2-11 Map legendsexplain what the symbolson maps represent.

A

B

C


1. Compare and contrast Mercator and gnomonic projections. What are theseprojections most commonly used for?

2. How is a conic projection made? Why isthis type of projection best suited formapping small areas?

3. What is a contour line? How are areas of depression represented on a topo-graphic map?

4. A topographic map has a fractional scaleof 1:80 000. The units are in centimeters.If two cities are 3 km apart, how far apartwould they be on the map?

5. Thinking Critically The equator is the onlyline of latitude that is a great circle. Why?

SKILL REVIEW

6. Interpreting Scientific Illustrations UseAppendix D to draw symbols in theirappropriate colors for the following features: barn, school, church, orchard,woods, perennial stream, marsh, and primary highway. For more help, refer to the Skill Handbook.

Figure 2-12 The map scaleand legend shown here arefrom a map of the RockyMountain area in Montana.

A fractional scale expresses distance as a ratio, such as 1:63 500.This means that one unit on the map represents 63 500 units onEarth’s surface. One centimeter on a map, for instance, would beequivalent to 63 500 cm on Earth’s surface. The unit of distance maybe feet or meters or any other measure of distance. However, theunits on each side of the ratio must always be the same. A large ratioindicates that the map represents a large area, while a small ratioindicates that the map represents a small area. A map with a largefractional scale such as 1:100 000 would therefore show less detailthan a map with a small fractional scale such as 1:1000. Figure 2-12shows the map scale and legend found on a typical map.



2.3 Remote Sensing 37

OBJECTIVES

• Compare and contrastthe different forms ofradiation in the electro-magnetic spectrum.

• Discuss how satellitesand sonar are used tomap Earth’s surface andits oceans.

• Describe the GlobalPositioning System.

VOCABULARY

remote sensingelectromagnetic spectrumfrequencyLandsat satelliteTopex/Poseidon satelliteGlobal Positioning Systemsonar

2.32.3 Remote Sensing

Until recently, mapmakers had to go on-site to collect the dataneeded to make maps. Today, advanced technology has changed theway maps are made. The process of collecting data about Earth fromfar above Earth’s surface is called remote sensing. Let’s examine howsatellites, which use remote sensing, gather information aboutEarth’s surface.

THE ELECTROMAGNETIC SPECTRUMSatellites, such as the one being launched in Figure 2-13, detect dif-ferent wavelengths of energy reflected or emitted from Earth’s sur-face. This energy has both electric and magnetic properties. Thus, itis referred to as electromagnetic radiation. Visible light is a form ofelectromagnetic radiation. Other types include gamma rays, X rays,ultraviolet waves, infrared waves, radio waves, and microwaves.

Wave Characteristics All electromagnetic waves travel at thespeed of 300 000 km/s in a vacuum, a value commonly referred to asthe speed of light. In addition, electromagnetic waves have distinct

Figure 2-13 Landsat 7, launched in 1999, is equipped to measure differences in thermal energy emitted by features on Earth’s surface.

wavelengths. The arrangement of electromagnetic radiation accord-ing to wavelengths is called the electromagnetic spectrum, asshown in Figure 2-14. Gamma rays have wavelengths of less than0.000 000 000 01 m, while radio waves have wavelengths of 100 000m. An electromagnetic wave also can be described according to itsfrequency, which refers to the number of waves that pass a particu-lar point each second. Gamma rays have the highest frequencies andradio waves have the lowest. The wavelengths, speeds, and frequen-cies of electromagnetic waves help determine how the energy is usedby different satellites to map Earth.

LANDSAT SATELLITESA Landsat satellite receives reflected wave-lengths of energy emitted by Earth’s sur-face, including some wavelengths of visiblelight and infrared radiation. Features onEarth’s surface, such as rivers and forests,radiate warmth at slightly different fre-quencies. Thus, these features show up asdifferent colors in images such as the one inFigure 2-15. To obtain such images, eachLandsat satellite is equipped with a movingmirror that scans Earth’s surface. This mir-ror has rows of detectors that measure theintensity of energy received from Earth.This information is then converted bycomputers into digital images that showlandforms in great detail. Landsat 7,launched in 1999, maps 185 km at a timeand scans the entire surface of the planet in16 days. Landsat data also are used to studythe movements of Earth’s plates, rivers,earthquakes, and pollution.

102 10 1105 104 103 10–1 10–2 10–3 10–4 10–5

106 107

Infrared radiationMicrowavesRadio waves

108103 104 105 109 1010 1011 1012 1013 1

Note: Wave not to scale


Figure 2-14 In the electromagnetic spectrum, the waves with the longestwavelengths have the lowest frequencies.

Figure 2-15 The blue areain this Landsat 7 imageshows the range of a firethat occurred in Los Alamos,New Mexico, in May 2000.

10–7 10–8 10–9 10–10 10–11 10–12 10–13 10–14 10–15

1015 1016

Ultravioletradiation

Visiblelight

Visiblelight X rays Gamma rays

1017 1018 1019 1020 1021 1022 1023 Frequency(hertz)

Wavelength(meters)10–6

1014

Figure 2-16 In theTopex/Poseidon satellite,an emitter sends an out-going signal to the surfaceof the ocean. A receivertimes the returning signal.The distance to the ocean’ssurface is calculated usingthe known speed of lightand the return time.


ReceiverReceiver

EmitterEmitter

OutgoingOutgoing

ReturningReturning

TOPEX/POSEIDON SATELLITEOther satellites, such as the Topex/Poseidon satellite, shown in Figure2-16, use radar to map features on the ocean floor. Topex stands for“topography experiment.” Radar uses high-frequency signals that aretransmitted from the satellite to the surface of the ocean. A receivingdevice then picks up the returning echo as it is reflected off the water.The distance to the water’s surface is calculated using the known speedof light and the time it takes for the signal to be reflected. Variations in time indicate the presence of certain features on the ocean floor.For instance, ocean water bulges over seafloor mountains and forms depressions over seafloor valleys. These changes are reflected insatellite-to-sea measurements. Based on these data, computers createmaps of ocean-floor features. The Topex/Poseidon satellite also hasbeen used to study tidal changes and global ocean currents.

THE GLOBAL POSITIONING SYSTEMThe Global Positioning System (GPS) is a radio-navigation systemof at least 24 satellites that allows its users to determine their exactposition on Earth. Each satellite orbits Earth and transmits high-frequency microwaves that contain information about the satellite’sposition and the time of transmission. The orbits of the satellites arearranged so that signals from several satellites can be picked up atany given moment by a GPS user equipped with a hand-heldreceiver, as shown in Figure 2-17. The receiver calculates the user’sprecise latitude and longitude by processing the signals emitted bymultiple satellites. The satellites also can relay information about ele-vation, direction, and speed. GPS technology is used extensively fornavigation by airplanes and ships. However, it is also used to detectearthquakes, create maps, and track wildlife. Lately, it has becomeincreasingly popular among hikers, backpackers, and other travelers.

SEA BEAMSea Beam technology is similar to the Topex/Poseidon satellite in thatit is used to map the ocean floor. However, Sea Beam is located on aship rather than on a satellite. To map ocean-floor features, Sea Beamrelies on sonar, which is the use of sound waves to detect and mea-sure objects underwater. First, a sound wave is sent from a shiptoward the ocean floor, as shown in Figure 2-18. A receiving devicethen picks up the returning echo when it bounces off the seafloor.Computers on the ship calculate the distance to the ocean bottom


Figure 2-17 This hiker isusing a hand-held, GPSreceiver.

To learn more about mapping, go to theNational GeographicExpedition on page 864.

using the speed of sound in water and the time it takes for the soundto be reflected. A ship equipped with Sea Beam has more than adozen sonar devices aimed at different parts of the sea. Sea Beamtechnology is used by fishing fleets, deep-sea drilling operations, andscientists such as oceanographers, volcanologists, and archaeologists.


1. What is the electromagnetic spectrum?Sequence the forms of electromagneticradiation from longest wavelength toshortest wavelength.

2. How do Landsat satellites collect and analyze data to map Earth’s surface?

3. What features are mapped by theTopex/Poseidon satellite? Describe themapping process.

4. Describe the Global Positioning System.

5. Thinking Critically Explain why electro-magnetic waves with short wavelengthshave higher frequencies than electromag-netic waves with long wavelengths.

SKILL REVIEW

6. Concept Mapping Use the followingwords and phrases to complete a conceptmap about remote sensing. For morehelp, refer to the Skill Handbook.

uses visible light and infrared

radiation to map Earth’s surface

uses microwaves to determine

location of user

GPS

remote sensing

Landsat satellite

uses radar tomap ocean floor

Topex/Poseidonsatellite

Figure 2-18 In a shipequipped with Sea Beam, a sound wave is sent to the ocean floor. The wavebounces off the seafloorand its returning echo isrecorded by a receiver onthe ship. The distance tothe ocean floor is then calculated using the knownspeed of sound in waterand the return time of thesound wave.




ProblemHow can you use a topographic map tointerpret information about an area?

Materialsruler stringpencil

Using a Topographic Map

Topographic maps show two-dimensional representationsof Earth’s surface. With these maps, you can determine

how steep a hill is, what direction streams flow, and wheremines, wetlands, and other features are located.

Preparation

Procedure

Analyze

Conclude & Apply

1. What is the contour interval?2. Calculate the stream gradient of Big

Wildhorse Creek from the Gravel Pitin section 21 to where the creekcrosses the road in section 34.

3. What is the highest elevation of thejeep trail? If you followed the jeep trailfrom the highest point to where itintersects an unimproved road, what

would be your change in elevation?4. If you started at the bench mark

(BM) on the jeep trail and hikedalong the trail and the road to theGravel Pit in section 21, how farwould you have hiked?

5. What is the straight line distancebetween the two points in question 4?What is the change in elevation?

1. Use the map to answer the followingquestions. Be sure to check the map’s scale.

2. Use the string to measure distancesbetween two points that are not in astraight line. Lay the string along the

curves, and then measure the distance by laying the string along the ruler.

3. Remember that elevations on UnitedStates Geological Survey maps aregiven in feet.

1. Does Big Wildhorse Creek flow allyear round? Explain your answer.

2. What is the shortest distance alongroads from the Gravel Pit in

section 21 to the secondary highway?3. Draw a profile of the land surface

from the bench mark in section 22 tothe Gravel Pit in section 33.

SCALE 1:24 000

vary in size from 50 000 km2 to as much as 350 000 km2. Polar bear ranges are muchgreater than those of other mammals becausethe sea ice on which they live changes from season to season and year to year.

Procedure1. Calculate the range of a polar bear that

travels for six hours a day for seven days at a speed of 5.5 km/h.

2. Calculate how far a polar bear could swim insix hours at a speed of 10 km/h.

3. Convert your answers for questions 1 and 2into U.S. units.

Challenge1. Assume that polar bears do equal amounts of

swimming and walking, and that they travel anaverage of four hours a day. Use your calcula-tions and a world map or globe to determinewhether a polar bear could travel around thecircumference of Greenland in a year.


The Ring of LifeThe borders of five countries—Russia,

Norway, Greenland, Canada, and the UnitedStates—meet in a rough U-shape around theArctic Ocean. The vast majority of this region iscovered with ice some 2 m thick. In a climatewhere average winter temperatures hover around–35°C, survival is tenuous. The southern bound-aries of this region, however, teem with life. Polarbears, walruses, beluga whales, fish, birds, andseals make the arctic circle their home.

Animal AdaptationsPolar bears in particular thrive where the

ocean meets the shoreline, an area of constantfreezing and thawing. Supremely adapted to thisenvironment, they have long necks that helpthem keep their heads above water and hugeforepaws that act as paddles. Light-colored furprovides camouflage to help them hunt, and anouter coat of hollow hairs makes the half-tonbears fairly buoyant in the water.

Traveling BearsPolar bears can swim for an average of

approximately 96.5 km without stopping for arest. They have been tracked on land traveling30 km a day for several days in a row. A polarbear’s home range—the area in which it hunts,mates, and cares for its young—may be around259 000 km2. The home ranges of polar bears

Thriving in the ArcticHow do you envision conditions in the arctic circle, which surroundsthe north pole? Barren of life? Not quite! More than 20 000 polar bearslive in this region, along with many other species. These hardy animalshave unique adaptations that allow them to survive the harsh climate.

Polar bear

To find out more about polar bears, visitthe Earth Science Web Site at earthgeu.com

http://earthgeu.com

Summary

Vocabularycartography (p. 27)equator (p. 27)International Date

Line (p. 31)latitude (p. 27)longitude (p. 29)prime meridian

(p. 29)

Vocabularyconic projection

(p. 32)contour interval

(p. 34)contour line (p. 33)gnomonic projection

(p. 33)map legend (p. 35)map scale (p. 35)Mercator projection

(p. 32)topographic map

(p. 33)

Vocabularyelectromagnetic

spectrum (p. 38)frequency (p. 38)Global Positioning

System (p. 40)Landsat satellite

(p. 38)remote sensing

(p. 37)sonar (p. 40)Topex/Poseidon

satellite (p. 39)

Main Ideas• Cartographers use a grid system to locate exact positions on

Earth. Lines of latitude refer to distances north and south of theequator. Lines of longitude refer to distances east and west ofthe prime meridian.

• Earth is divided into 24 time zones. Each zone represents a dif-ferent hour. The International Date Line, or 180° meridian, is thetransition line for calendar days. The calendar advances to thenext day in each time zone at midnight.

Main Ideas• Maps are flat models of Earth’s surface. All maps contain some

sort of distortion in the shapes or areas of landmasses.• Maps are made by transferring points and lines on a globe

onto paper. Mercator projections and gnomonic projections are commonly used for navigation by ships and planes. Conicprojections are best suited for mapping small areas.

• Topographic maps show changes in elevation of Earth’s surface.Contour lines connect points of equal elevation. A map legendexplains the symbols on a map. A map scale shows the relation-ship between distances on a map and actual distances on Earth.

Main Ideas• The process of gathering data about Earth from far above the

planet is called remote sensing. The electromagnetic spectrumshows the arrangement of electromagnetic radiation, which isoften used by remote-sensing devices to map Earth.

• Landsat satellites use visible light and infrared radiation to mapEarth’s surface. The Topex/Poseidon satellite uses radar to mapfeatures on the ocean floor.

• The Global Positioning System is a satellite-based navigationsystem that allows a user to pinpoint his or her exact locationon Earth.

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SECTION 2.1

Latitude andLongitude

SECTION 2.2

Types of Maps

SECTION 2.3

Remote Sensing

Study Guide 45earthgeu.com/vocabulary_puzzlemaker

http://earthgeu.com/vocabulary_puzzlemaker


1. What feature on a map shows the ratio of mapdistance to actual distance on Earth?a. map legend c. map symbolb. map scale d. contour line

2. What type of map shows changes in elevation onEarth’s surface?a. Mercator projection c. topographic mapb. gnomonic projection d. GPS

3. Which of the following is NOT true of lines of longitude?a. They are semicircles.b. They measure distances east and west of the

prime meridian.c. They run from pole to pole.d. They are parallel lines.

4. What technology is used to map seafloor features?a. conic projectionsb. Topex/Poseidon satellitec. the Global Positioning Systemd. Landsat satellite

5. What is the main disadvantage of a Mercatorprojection?a. It distorts areas near the equator.b. It distorts the shapes of landmasses.c. It distorts areas near the poles.d. It does not show true direction.

6. What is the reference point for lines of latitude?a. the equatorb. the prime meridianc. the International Date Lined. the 180° meridian

7. What is the distance of one degree of latitude?a. 11 km c. 40 000 kmb. 111 km d. 1.85 km

Understanding Main Ideas 8. Some areas have lower elevations than the surrounding land. Which of the following rep-resents these areas on a topographic map?a. index contoursb. contour intervalsc. depression contour linesd. map legends

9. What is the Global Positioning System? Describe how it might be used by a hiker lost in the woods.

10. Compare and contrast a verbal scale, a graphicscale, and a fractional scale.

11. Would a topographic map of the Great Plainshave a large or small contour interval? Explain.

12. Why can’t two contour lines overlap?

13. How could you leave home on Monday to go sailing, sail for an hour on Sunday, and returnhome on Monday?

14. What is a map legend? Give examples of featuresfound in a map legend.

15. What type of map would best show true direction?

16. Do closely spaced contour lines indicate a steepslope or a gradual slope? Explain.

Applying Main Ideas

WHERE HAVE I HEARD THAT BEFORE?If you don’t know the definition of a word, youcan usually work through the question by think-ing about how you’ve heard the word usedbefore. Think about the context in which theword was used. This will narrow its meaning.

Test-Taking Tip

earthgeu.com/chapter_test

http://earthgeu.com/chapter_test

Assessment 47

1. What is the reference point for lines of longitude?a. the equatorb. the prime meridianc. the International Date Lined. the 360th meridian

2. Which would be most useful if you were lostin the Sahara desert?a. Landsat satelliteb. Topex/Poseidon satellitec. Global Positioning Systemd. topographic map of Africa

USING MAPS Use the map to answer questions 3 and 4.

3. Roughly how many degrees of longitudedoes the United States cover?a. 10° b. 20° c. 30° d. 40°

4. Roughly how many degrees of latitude doesthe United States cover?a. 10° b. 15° c. 20° d. 25°

17. Approximately how many kilometers separateOrlando, Florida, at 29° north latitude andCleveland, Ohio, at 41° north latitude?

18. If it is 10 A.M. in Syracuse, New York, at 76° westlongitude, what time is it in Athens, Greece, at24° east longitude?

Use the map to answer questions 19–21.

19. Copy the map shown here. What is its contourinterval?

20. Based on the contour interval, label the elevations of all the contour lines.

21. Does the map represent a flat or hilly terrain?Explain.

22. Would a person flying from Virginia to Californiahave to set his or her watch backward or forward? Explain.

23. If you wanted to study detailed features of a vol-cano on the island of Hawaii, would you use amap with a scale of 1:150 or 1:150 000? Why?

24. Based on what you have learned in this chapter,infer how astronomers map objects in the night sky.

25. Which direction would you travel along Earth’ssurface so that your longitude would not change?Explain your answer.

Thinking Critically

Standardized Test Practice

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earthgeu.com/standardized_test

http://earthgeu.com/standardized_test

The Nature of ScienceEarth Science Earth science is divided intofour areas of specialization. Astronomy studiesobjects beyond Earth’s atmosphere. Meteorologystudies the atmosphere. Geology studies the mater-ials of Earth and the processes that form them.Oceanography studies the oceans. The applicationof scientific discoveries is technology. Earth is madeup of interacting systems. The lithosphere includesthe rocks that make up the crust and upper mantle.The atmosphere is the gas layer that surroundsEarth. The hydrosphere is Earth’s water. The bio-sphere is all of the life and habitats on Earth.

48 UNIT 1

Methods and Communication Most sci-entific methods include defining the problem, statinga hypothesis, testing the hypothesis, analyzing theresults of the test, and drawing conclusions. In thetesting step, variables are factors in an experimentthat change. A dependent variable changes inresponse to the independent variable. A control is astandard for comparison. Scientists use standardunits of SI—liter, meter, second, kilogram, Newton,and degree Celsius. Scientists also use scientific nota-tion, in which a number is expressed as a multiplierand a power of ten. Scientists communicate inreports and papers, and use tables, graphs, and mod-els. A scientific theory is an explanation based onobservations from repeated experiments. It is validonly if it is consistent with observations, leads totestable predictions, and is the simplest explanation.Scientific theories are changed if they are found tobe incorrect. A scientific law is a basic fact thatdescribes the behavior of a natural phenomenon.

Earth Science

For a preview of Earth science, study this GeoDigest before you read the chapters.After you have studied the unit, you can use the GeoDigest to review.

F O C U S O N C A R E E R S

Science Teacher Science teachers often provide astudent’s first exposure to scienceand may spark a life-long interestin a particular topic. High schoolscience teachers must have atleast a bachelor’s degree, oftenfrom a five-year program, with anemphasis in their area of interest,such as Earth science.

GeoDigest 49

Understanding Main Ideas1. Which of the following is an area of special-

ization in Earth science?a. hydrosphere c. meteorologyb. Mercator projection d. remote sensing

2. What happens if a scientific theory is foundto be incorrect?a. It is published.b. It is changed.c. It becomes a scientific law.d. It becomes a control.

3. Which type of map shows changes in eleva-tion of Earth’s surface?a. conic projection c. topographic mapb. gnomonic projection d. latitude map

4. What does a map legend contain?a. contour linesb. longitude linesc. latitude linesd. the symbols used in a map

5. What is the application of science called?a. technology c. scientific lawb. latitude d. theory

Thinking Critically1. Describe the steps commonly used in scientific

methods.2. Why isn’t a conic projection used to navigate

a ship or aircraft?

Earth Science

Mapping Our WorldLatitude, Longitude, and MapsCartographers use a grid system of latitude andlongitude to locate exact positions on Earth.Latitude refers to distances north and south of theequator. Longitude refers to distances east and westof the prime meridian. Earth is divided into 24 timezones, with each zone representing a different hour.The International Date Line, or the 180° meridian, isthe transition line for calendar days. Maps are flatmodels of Earth’s round surface, thus all maps con-tain some sort of distortion. Maps are made bytransferring points and lines on a globe onto paper.A map legend explains map symbols. A map scaleshows how distances on a map and actual dis-tances on Earth are related. Mercator and gno-monic projections are used for aircraft and shipnavigation. Conic projections are suited to mappingsmall areas. Topographic maps show changes in ele-vation of Earth’s surface. Gathering data about

Earth’s Land AreaContinent Area in km2

Asia, Middle East 44 579 000Africa 30 065 000North America 24 256 000South America, 17 819 000

Central America, and Caribbean

Antarctica 13 209 000Europe 9 938 000Australia and Oceania 7 687 000Earth Total 148 429 000

Vital Statistics

Earth from far above is called remote sensing.Examples of remote-sensing devices includeLandsat satellites, the Topex-Poseidon satellite, andthe Global Positioning System. These different typesof technology can be used to map Earth’s surfaceand oceans, and to locate places on Earth.

A S S E S S M E N T

chapter 2: mapping our world

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