lesson 3: heating earth's surface

26 STC/MS™ CATA S T R O P H I C EV E N T S

INTRODUCTIONHave you ever walked barefoot on a sidewalk inthe early summer? The concrete probably felthot against your feet. But if you jumped into apool on the same day, you might have felt cold.How could this be?

Part of the explanation has to do with the waythe earth’s surfaces receive and give off heat. Allthe surfaces on the earth absorb some of thesun’s energy and give off heat to the air as theycool—but they do it at different rates. Did youknow that the earth’s surfaces heat and cool dif-ferently? In this lesson, you will investigate therates at which soil and water heat and cool. Inlater lessons, you will see that this uneven heat-ing affects the circulation of air on the earth andhelps create storms.

3Heating Earth’s Surfaces

LESSON

OBJECTIVES FOR THIS LESSON

Observe and record the rates at whichequal volumes of soil and water heatand cool.

Graph and analyze the heating andcooling rates of soil and water.

Explain what happens to energy fromthe sun when it reaches the earth.

Read and interpret a data table.

Describe the atmosphere and its layers.

Hot concrete and cool water are signs that the earth’s

surfaces heat and cool at different rates.

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STC/MS™ CATA S T R O P H I C EV E N T S 27

Getting Started

1. Your teacher will review your homeworkwith you and your class. Following thequestions on Student Sheet 2.1, discusswhat you know about thunderstorms;where typhoons, hurricanes, andcyclones are likely to form; and the simi-larities and differences between torna-does and hurricanes.

2. What do you think causes storms? Discussthis with your class.

3. Brainstorm with your class ways youmight investigate how soil and water heatand cool.

MATERIALS FORLESSON 3

For you1 completed copy of

Student Sheet 2.1:Thunderstorms,Tornadoes, andHurricanes

1 copy of StudentSheet 3.1a:Testing the Heatingand Cooling Ratesof Soil and Water

1 copy of StudentSheet 3.1b:Interpreting a DataTable

1 metric ruler1 blue pencil or pen1 red pencil or pen1 sheet of graph

paper

For your group1 tote tray2 glass beakers2 metal digital

thermometers 2 cardboard strips1 clamp lamp with

bulb2 bookends1 stopwatch1 transparency of

graph paper

2 overheadtransparencymarkers (redand blue) SoilWater

1 metric rulerAccess toelectricity


LESSON 3 HE AT I N G EA R T H’S SU R FA C E S

Figure 3.1 Setting up the investigation. How will you make certain it is a fair test?

Inquiry 3.1Investigating Rates ofHeating and Cooling

PROCEDURE

1. Review with your teacher how to use astopwatch and digital thermometer.

2. As a class, go over Procedure Steps 5through 13. Observe as your teacherdemonstrates the steps needed to com-plete the investigation.

3. With your class, review the Safety Tips forthis inquiry.

4. Review Student Sheet 3.1a: Testing theHeating and Cooling Rates of Soil andWater as your teacher discusses it.

SAFETY TIPS

Keep water awayfrom all electricaloutlets.

Avoid touchingthe hot lamp dur-ing the investiga-tion and while thelamp is cooling.

Tuck electricalcords beneathwork areas. Donot drape cordsacross trafficareas.

Be careful withthe sharp end ofthe thermometers.

5. Think about this investigation as if it werea race or a test between equal volumes ofsoil and water. Under Question 1 on thestudent sheet, record all the things youthink you will need to keep the same forthe beakers.

6. Pick up your group’s remaining materials.To set up a fair test, get equal volumes ofsoil and water from the distribution center.

7. Set up the materials as shown in Figure3.1. Insert each thermometer approxi-mately 2.5 centimeters (cm) into the soilor water in each beaker. Do not allow thetip of the thermometer to touch the bot-tom of the beaker. Use the small hole inthe cardboard to hold each thermometerupright. Turn on the thermometers.

100 mL soil 100 mL water



the empty container set out by yourteacher, where it can cool.

D. Return your materials to your tote trayfor the next class.

E. Your teacher will tell you where to putyour lamp.

15. Complete Student Sheet 3.1a. Calculatethe overall change in temperature of eachbeaker during heating and cooling. Forthe Heating columns, subtract the firsttemperature (0:00 minutes) from the lasttemperature (10:00 minutes). For theCooling columns, subtract the last tem-perature (20:00 minutes) from the firsttemperature (10:00 minutes). Give youranswers to the nearest 0.1 degree.

16. How might you plot your data on a graphso it is easy to read? Before you begin,discuss your ideas with your class.

17. Work with your group to create one graphon an overhead transparency. While youdo, consider these questions:

A. What title will you give your graph?

B. How will you label each axis to showthe temperature and time changes?

C. What will be the first number on eachaxis? How will you space the numbers oneach axis? How many degrees will eachinterval between the numbers represent?

D. What techniques will you use to makethe graph more readable?

18. Review your group’s completed graph withthe class or with another group. Analyzethe graphs using the questions inProcedure Step 17. How easy are thegraphs to interpret?

8. Allow the thermometers to sit in eachbeaker until the temperature readings nolonger show any sign of changing.

9. While you are waiting for the temperaturereadings to stop changing, make somepredictions. What do you think will hap-pen to the temperature of the soil and thewater when you turn on the lamp? Whatwill happen when you turn off the lamp?Why do you think this? Record your pre-dictions under Question 2 on StudentSheet 3.1a.

10. Do not turn on the lamp yet. After thereadings on the thermometers have stabi-lized, record the temperatures for boththe soil and the water in Table 1 onStudent Sheet 3.1a, across from 0:00 min-utes under the column labeled “Heating.”

11. Turn on the lamp.

12. Start your stopwatch. Read the tempera-ture of both materials to the nearest 0.1 ºCevery minute for 10 minutes. Record yourdata in the table.

13. At the end of 10 minutes, turn off yourlamp but let the watch keep running.Quickly record the 10-minute tempera-ture for soil and water in the Heatingcolumns. Record the same number acrossfrom 10:00 minutes at the top of theCooling columns. Continue reading andrecording the Cooling temperature for soiland water every minute for 10 minutes.

14. When you finish, clean up.

A. Turn off the digital thermometers.

B. Dispose of the water from your beaker ina sink or bucket.

C. Do not throw away the soil. Pour it into



WEATHER VERSUS CLIMATEIn Part 1 of Catastrophic Events, the words“weather” and “climate” appear quite often.Although both terms have to do with the stateof the atmosphere, they do not mean exactlythe same thing. How are they different?

Weather is the state of the atmosphere at aparticular time and place. For example, afriend may ask, “What was the weather likewhen you were at the beach yesterday?” Yourfriend wants to know about the weather on acertain day at a certain place. Your answermight be, “In the morning it was rainy, butthen it got really hot and windy.”

This answer refers to three important ele-ments of weather: moisture, temperature, andwind speed. (Another element is atmosphericpressure.) Remember that weather is the stateof the atmosphere. So, where there is noatmosphere, there is no weather like that onthe earth. This means that beyond the earth’satmosphere in space, there is no weather aswe know it.

Climate refers to weather patterns that arecharacteristic of a region or place for manyyears. For example, you might describe thesouthwestern region of the United States ashaving a hot, dry climate. Or you might saythat the climate of a town near the coast ismore moderate than the climate of a town100 kilometers inland.

19. On your own, graph your group’s datausing graph paper and the tips you dis-cussed with your teacher and the class.Title your graph.

REFLECTING ON WHAT YOU’VE DONE

1. Answer these questions. Then discussthem with the class.

A. How would you describe the heatingand cooling rates of soil and water inthis investigation?

B. Which material held its heat longer?

C. What factors may have influencedyour results?

D. Reread the Introduction to this lesson.Can you explain now why concrete feelshot under your feet in early summer,while water in a pool feels cold?

E. On the basis of your investigation,how do you think oceans absorb andhold heat? How do you think the temper-ature of the ocean compares with thetemperature of the land nearby?

2. Discuss “The Source of Earth’s Heat,” onpages 31–33, which you read for home-work, with your class. Review the ques-tions at the end of the reading selection.

3. Complete Student Sheet 3.1b: Interpretinga Data Table. You should also read “TheAtmosphere: A Blanket of Air,” on pages34–36.

4. Read “Weather Versus Climate.” Lookahead to Lessons 4 and 5. In theselessons, you will investigate how theuneven heating of the earth’s surfacesaffects weather in the earth’s atmosphere.



The Source of Earth’s Heat

Earth’s atmo-

sphere and sur-

faces absorb and

reflect the sun’s

energy. Some of

the absorbed

energy is given

off as heat.

That sounds simple enough, right? Wrong!Only a small amount of the sun’s energy actuallyreaches the earth. The rest of the sun’s energyreaches out throughout space. Of the smallamount that does reach the earth, about half isabsorbed by land and the oceans. The rest isreflected back into space or absorbed by the thinblanket of air—the atmosphere—that surroundsthe earth.

Earth has many different kinds of surfaces.Materials such as soil, rock, and water absorband give off energy at different rates. Look atthe illustration below. A surface of snowabsorbs only 5 percent of the solar energy itreceives, while a dark forest absorbs 95 percentof the solar energy it receives. The temperatureof a surface, such as snow or a forest, is anindication of the amount of the sun’s heat energythat has been absorbed. That is, it is a measureof how hot or cold a material is. Differences inhow the earth’s surfaces absorb and give offenergy are part of the reason that winds formand weather patterns change.

You head home from school. The air is warm,moist, and breezy. Raindrops begin to hit thepavement beneath your feet and you hear thun-der in the distance. Lightning flashes. Huge,anvil-shaped clouds hover overhead. A thunder-storm is headed your way.

What causes the weather and its storms? Partof it has to do with the effects of heat from thesun.

Solar EnergyEnergy from the sun—called solar energy—isthe source of most of the earth’s heat on land, inthe oceans, and in the atmosphere. Solar energymakes its way through the vacuum of space tothe planet Earth by a process known as radia-tion. Some of this solar radiation is visible aslight, and some of this radiation (heat, for exam-ple) is invisible. The interaction of solar energywith air, soil, and water on the earth createswind, rain, and other elements of weather.

FORESTS, LAND,AND WATER Reflected

Heat

Absorbed

Reflected

Heat

Absorbed

Reflected

ICE ANDSNOW

ATMOSPHERICPARTICLESAND GASES

Absorbed

Heat



December than in June. If closeness to the sunwere responsible for how warm the earth was,this would mean that everyone on the earthwould have summer in December. You knowthis is not true if you live in the NorthernHemisphere.

It is the tilt of the earth’s axis that is respon-sible for changes in seasons. From March 21through September 21 (or 22, depending onthe year), the Northern Hemisphere tiltstoward the sun. This means that the NorthernHemisphere receives more solar radiation thanthe Southern Hemisphere does during thistime. More direct sunlight causes warmerweather. From September 23 through March19, the opposite is true. The Southern

Seasons Make a DifferenceHow air, land, and water absorb and give offenergy plays an important role in weather. Butthis is not the only factor that determinesweather. Earth, like all the planets, revolvesaround the sun. Earth also spins on its ownaxis, which is tilted. The tilt of the earth’s axisbarely changes, but the part of the earth thatgets the most solar energy does change. This isbecause the tilted earth orbits around the sun.

What do you think causes the seasons? Manypeople believe that seasons depend on how faraway the earth is from the sun. That mightseem logical, but consider this: the earth travelsin an ellipse, or oval, around the sun. At certaintimes, the earth is slightly closer to the sun in

From March 21 through September 21, the Northern Hemisphere tilts toward the sun and has spring and summer. The

Southern Hemisphere tilts away from the sun and has fall and winter. The equator is warm all year round. (Diagram is

not drawn to scale.)

NorthernHemisphere:summer

Sun

NorthernHemisphere:winter

March 20

December21

SouthernHemisphere:summer

September 22

SouthernHemisphere:winter

June 21



around the globe. Gases and clouds in theatmosphere hold in the amount of heat neededto keep the earth livable. The atmosphereaffects the amount of solar energy that reachesthe earth and protects it from the sun’s moreharmful radiation. The atmosphere and itsweather keep most of the earth’s surfaces warmenough for life to exist as we know it. �

QUESTIONS

1. On the basis of this reading, what does thelamp in Inquiry 3.1 represent?

2. How does solar energy travel?3. What happens to energy from the sun

when it reaches the earth’s atmosphereand surfaces?

Hemisphere tilts toward the sun and haswarmer weather. On December 21, for exam-ple, the Southern Hemisphere celebrates thefirst day of summer, while the NorthernHemisphere begins winter.

On two days of the year (March 20 andSeptember 22), neither hemisphere tiltstoward the sun. Therefore, both hemispheresreceive the same amount of the sun’s energy.Except at the poles, night and day are almostequal in length all over the world. These twodays are called the equinox. (To rememberthis term, think of “equal night.”)

Thank Goodness for Weather! Without energy from the sun, all of the thingsthat we take for granted on the earth, includingthe weather, would not exist. Weather distrib-utes heat and precipitation (such as rain)



atmosphere than it does at the equator. Moreatmosphere results in more reflecting andabsorbing of the sun’s rays. (See the illustra-tion.) This causes less solar energy to reach theearth’s surfaces at the poles. And when thesun’s energy does reach the poles, ice and snowreflect a portion of it away from the earth.Therefore, even though the North Pole experi-ences 24 hours of continuous daylight on June21, it is still colder than cities farther south.

The composition of the atmosphere alsoaffects the amount of solar energy that reachesthe earth. Most of the atmosphere is made up ofnitrogen. But oxygen, carbon dioxide, variable

What makes the earth different from all otherplanets in the solar system? Its atmosphere does!The atmosphere acts like a blanket of air aroundthe earth. That means that the atmosphere holdsin the amount of heat needed to keep the earthlivable. It also affects that amount of solar energythat reaches the earth and protects it from thesun’s more harmful radiation.

Just Passing ThroughEarth’s atmosphere absorbs and reflects solarenergy. As a result, the sun does not heat thepoles and the equator evenly. Why not? At thepoles, sunlight has to pass through more

The Atmosphere: A Blanket of Air

Sun’s rays

Earth’s atmosphere absorbs and reflects solar energy. At the poles, because of the curve of the earth, sunlight has to

pass through more atmosphere to reach the earth’s surface than the sunlight that reaches the equator. This is one

reason why the poles are colder than other parts of the earth.



heated by the surface below it.)The temperature in the troposphere usually

gets colder as one goes higher. This is becausethe air is thinner or less dense the farther onegoes from the earth’s surface. So the tempera-ture of the air at the top of the tallest mountainis always colder than the air at the base of themountain.

Above the troposphere is the stratosphere.The stratosphere protects the earth from thesun’s harmful radiation. Here the temperatureis nearly constant. Very little water vapor orother gases are present; water vapor clouds arerare. Somewhere in the middle is a protectiveozone layer. Ozone is a special form of oxygen,O3. It is an almost colorless gas with an odorsimilar to weak chlorine. The ozone layer trapsthe sun’s harmful ultraviolet radiation andkeeps it from reaching the troposphere.

The third layer of the atmosphere is themesosphere. At the top of this layer, the temper-ature decreases to about minus 90 °C beforereaching the final layers: the thermosphere andexosphere. There, the air is thin and the leastdense. Satellites and other spacecraft can travelin the thermosphere and exosphere with verylittle resistance. In the exosphere, the earth’satmosphere fades into the vacuum of outerspace. �

amounts of water vapor (water that has changedto a gas), and traces of other gases are also partof the mix. Although most of these gases neitherabsorb nor reflect solar energy, water vapor andcarbon dioxide do absorb solar energy and ener-gy given off from the earth. They are the main“greenhouse gases” that keep the planet’s atmo-sphere warm and livable. Without this propertyof the atmosphere, all of the solar energy wouldescape back into space. Earth’s surface would beso cold that any water would be permanentlyfrozen.

Multilayered AtmosphereThe force of gravity holds the earth’s atmo-sphere in place. The moon has no atmosphere.This is because its gravitational force is muchsmaller than that of the earth.

Think of the earth’s atmosphere as layers ofa cake. (See the illustration on page 36.) Thebottom layer, the troposphere, is where mostof the earth’s weather takes place. The tropo-sphere contains most of the water vapor in theatmosphere. Air moves in all directions in thetroposphere—up and down and sideways. Thisis due to the uneven heating created by radia-tion from the sun above and from the land andoceans below. (In Lessons 5 and 6, you willinvestigate what happens to air when it is

Nitrogen and oxygen make up the majority of the atmospheric gases.

Nitrogen: 78%

Oxygen: 21%

Trace gases, includingwater vapor: about 1%



500 km

280 km

Contains 78% nitrogen, 21% oxygenTroposphere

Very little turbulence; ozonelayer absorbs radiation here.Stratosphere

Temperatures decrease here to −90 °C; meteoroids burn up here.

Mesosphere

The ionosphere exists in the lowerthermosphere between 80 and280 km.

Temperatures here may reach ashigh as 1000 °C.

Space stations such as MIR andthe International Space Stationhave stable orbits at 320- to380-km altitude.

Northern lights occur here.

Thermosphere

Exosphere extends out to about1000 km; most satellites orbithere.

Exosphere

15 km

50 km

80 km

Scientists divide the

earth’s atmosphere

into five layers.



Your team has asoccer game onSaturday. You turnon the televisionto check out theweekend weather.Radar images onmulticolored mapsshow rain movingeast, away fromyour town. You logon to the nationalweather Web siteand find that thecurrent tempera-ture is just rightfor an outdoor soc-cer game.

In this age of 5-day weather fore-casts and colorfulcomputer displaysof the entire coun-try’s weather, it ishard to imaginenot being able tofind out tomor-row’s forecast. Butbefore the mid-1800s, farmersand ship captains,whose lives andjobs depended onthe weather, hadlittle informationto go on. Theyrelied on suchthings as clouds,

JOSEPH HENRY: The Father of Weather Forecasting

Joseph Henry

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branch of physical science.” For this reason,Henry decided to develop a “system of extendedmeteorological observations.” Observing theweather nationally, he thought, could solve “theproblem of American storms.”

Like any good scientist, Henry developed aplan of action. First, he needed weather infor-mation from around the country. So he estab-lished a network of about 150 volunteerobservers, a number that eventually grew toabout 600. The Smithsonian supplied the volun-teers with instructions, standardized forms,and, in some cases, instruments. The volunteerssubmitted monthly weather reports from theirarea. This included temperature, humidity,wind and cloud conditions, and rain and snowmeasurements. Analyzing this information

winds, the Farmer’s Almanac, animal behaviorsigns, and their own arthritic bones to makeguesses about the weather. But a scientistnamed Joseph Henry changed all of that.

If you have heard of Joseph Henry at all, itwas probably in connection with the Smith-sonian Institution—the national museum of theUnited States located in Washington, D.C.Joseph Henry was the Smithsonian’s first direc-tor. He is also considered by many to be the“father of weather forecasting.”

Spreading the Meteorological WordFrom the start, Henry was determined to keepthe Smithsonian’s focus on science. “Of lateyears, in our country,” he wrote, “more additionshave been made to meteorology than to any other

The telegraph was the new technology of the day. With a tap of a telegraph key, operators could send weather

information to the Smithsonian Institution.

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snow, black on those with rain, and brown onthose with cloudy skies. Under Henry’s direc-tion, the Smithsonian Institution had assem-bled, for the first time, “one view of the meteo-rological condition of the atmosphere over thewhole country.” Although crude by today’s stan-dards, the map attracted public attention andcreated discussions about the need for a nationalweather service.

Henry had solved the problem of getting theweather information to the SmithsonianInstitution. But how could he possibly analyzeall of the data pouring into the institution? Hefound a colleague, James H. Coffin, who put theweather information into useful reports. In1861, Coffin published two volumes of weatherinformation collected from 1854 to 1859.

required years of study, but eventually it helpedscientists to better understand storms and cli-mate differences across the country.

Henry’s plan also involved weather forecast-ing. He arranged for nearly 20 telegraph sta-tions around the country to report weatherinformation to the Smithsonian once a day.Compared with the monthly reports from vol-unteer observers, the information from tele-graph stations was not detailed. Telegraph oper-ators communicated only whether the sky wasclear or cloudy, whether it was raining or snow-ing, and wind direction.

Henry posted this information on a large mapin a public area of the Smithsonian Institution(see the picture on page 40). He put white discson cities with clear skies, blue on those with

A sketch of the “telegraph” Henry showed his classes at the Albany Academy. Although people credit Samuel B.

Morse with inventing the telegraph, Henry was actually tinkering with it years before.

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Meteorological Data Lead to NewDiscoveriesWith so much weather data now available,scientists made new theories and discoveriesabout weather. Henry theorized that localstorms are part of larger weather systems.Another scientist, Increase A. Lapham, usedthe data to show that a storm moved acrossthe country from west to east and that thepath could be plotted on a map. This findingmeant that communities could be warnedabout storms moving their way. Henry quicklyrealized that the telegraph could be a part ofsuch an early-warning system. In this way,people in the eastern parts of the countrycould be warned of storms coming their way.

What Happened to the Smithsonian’sWeather Network?In 1857, Henry planned to expand the weathernetwork he had set up into a storm warning

A Scientist Without a DegreeAlthough Joseph Henry was a famousAmerican scientist in his day, he neverwent to college. Born in Albany, NewYork, in 1797, Henry completed elemen-tary school as a child. He waited until his20s to enroll in the equivalent of a highschool. Henry’s life changed when heread George Gregory’s Lectures onExperimental Philosophy, Astronomy,and Chemistry. That experiencelaunched Henry on a lifetime explorationof nature.

Weather was just one of the subjectsthat fascinated Joseph Henry. In fact, hisstudies of electromagnetism laid thefoundation for the development of thetelegraph and telephone. These deviceschanged communications and humansociety dramatically.

Joseph Henry’s weather map was probably the first one in the country.

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system for the East Coast. But the Civil Warsoon overwhelmed the country and its tele-graph lines. When the war was over, Henry sug-gested that the federal government establish anational weather service.

Today’s weather service is very different fromHenry’s system of telegraphed observations anda simple wall map. Yet Henry’s vision of moni-toring weather on a large scale laid the founda-tion for the sophisticated forecasting system wehave today. Meteorologists have made greatprogress, but they’re still not always right. AsHenry finally admitted, it would probably beimpossible to achieve perfection in weatherforecasting, even with the best equipment. �

QUESTIONS

1. Describe how, in the 1850s, people couldfind out about the weather from theSmithsonian Institution. How is that differ-ent from the way we find out about weathertoday?

2. What role did Joseph Henry play in helpingestablish weather prediction centers? Whyare weather predictions important?

Weather systems follow wind patterns and move across

the United States from west to east.

lesson 3: heating earth's surface

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