DOCUMENT RESUME ERIC Clearinghouse on Teacher Education ... · That's when you see the yellow and blue layers of skin close together. The effect is green. (The sensations of anger

DOCUMENT RESUME

ED 236 110 SP 022 511

AUTHOR Markle, SandraTITLE Natural Wonder Notebook. (Five Installments of a

Monthly Column Appearing in Instructor Magazine,January-May 1983.]

INSTITUTION ERIC Clearinghouse on Teacher Education, Washington,D.C.

PUB DATE 83NOTE 14p.; Miniposters are not included.PUB TYPE Journal articles (080) -- Guides - Classroom Use'

Guides (For Teachers) (052)JOURNAL CIT Instructor; v92 n5-9 Jan-May 1983

EDRS PRICEDESCRIPTORS

IDENTIFIERS

ABSTRACT

C

MF01/PC01 Plus Postage.Discussion (Teaching Technique); ElementaryEducatioh; Elementary School Science; LearningActivities; *Natural Sciences; *Science Activities;Writing ExercisesPF Project

This science column includes background information,-discus ion questions, science activities, writing activities, and abiblio raphy on a different topic each month. The titles.of the fiveinstall ents included in this compilation are: (1) "Chameleons andOther Q ick-Change Artists"; (2) "Niagara Falls and Other SuperWaterfalls"; (3) "Elephants' Trunks and Other Nifty Sniffers"; (4)

"Tornado s and Other Big Winds"; and (5) "The Grand Canyon and Other_\

Hole in' (DC)

************************************************************************ Reproductions supplied by EDRS are the best that can be made *

from the original document. '*

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OLiJ

NATURAL WONDER NOTEBOOK

[FIVE INSTALLMENTS OF A MONTHLY-COLUMN APPEARING

IN INSTRUCTOR MAGAZINE, JANUARY-MAY 1983]

by Sandra Markle

Compiled by

The ERIC Clearinghouse on TeaCher Education.

Washington, DC

0

0

Reprinted froM INSTRUCTOR, January-May 1983. Copyright (c)

1983 by The Instructor Publications, Inc. Used by permission.

"PERMISSION TO REPRODUCE THISMATERIAL HAS BEEN GRANTED BY

Z. A cos oiu

U.S. DEPARTMENT OF EDUCATIONNATIONAL INSTITUTE OF EDUCATION

EDUCATIONAL RESOURCES INFORMATIONCENTER IERiC)

0 This docment has been reproduced asreceived horn fly. person or organizationoriginating it.

)C Minor changes have been made to imprcvereproduction quality.

TO THE EDUCATIONAL RESOURCES Points of view or opinions stated in this docu-

IN ORMATION CENTER (ERIC)." ment do not necessarily represent official NIE,position or policy.

I I I I

Ghazni asand other quick -chars art!sts

-Sanira_Markle

Leapin' Lizards! One moment it's brownand the next lime green! The fellow - knownas the chameleon is just doing what comesnaturallyexhibiting the natural phe-nomenon of changing its skin color. Thechameleon isn't the only one whose skincolor changes; humans, for instance, oc-casionally have found their faces turningcolors, much to their embarrassment!

This month INSTRUCTOR begins a regularscience feature called Natural WonderNotebook. Its first in a series of monthlyinvestigations into nature focuses on thephenomenon of changing skin color. Sci-ence consultant Sandra Markle will explorewhy this phenomenal: occurs, and she willtell you more about these in the animalkingdom who are able to make this "quickchange."

Accbmpanying this basic information isa colorful miniposter to display and a listof activities Sandra suggests you use withyour students. "The activities are reallyexercises in good thinking." she says. Thefirst section. Let's Talk, is a collection ofdiscussion questions that lead students toinquire and hypothesize about colorchanges in skin. The second section, Let'sInvestigate, has each sthdent make his orher.own paper chameleon and simulatethe color changes it experiences. The finalsection. Let's Write, encourages childrento organize the results of their discussionand experiments into effective forms ofwriting. Sandra believes that "when stu-dents are asked to talk over, investigate,and final' write about, a scientific phe-nomenon, they really begin to learn whatit's all about."

You may want to expand the study ofcolor change by having kids make a Natural^Wonder Corner in your room, completewith books, posters, and bulletin boardson the subject. (You might even enlargean encyclopedia diagram showing thechameleon's skin layers of various pig\Tments.) Enlist your media specialist's helpin finding other materials and check thebibikgraphy at the end of this feature.

When the month's over, store your mini -

poster and activity information in a spiralnotebook for easy reference. Then primeyour students for February's featureanda new corneron Niagara Falls. The fea-ture's general setup will be the sameaminiposter plus interesting facts and ac-tivities that encourage talking, experi-menting, and writing. Wonders to comein months ahead include elephants' trunksand other nifty sniffers, tornadoes, andthe Grand Canyon! This series will con-vince your kids that natural wonders areeven more wonderful when they get to knowthem.

The picture of the green lizard on the leftmay well be a picture of an angry cha-meleon. Or it May be that the colorfulfellow has just seen a heron fly over andhas been frightened green by its enemy.At any rate, chances are the chameleonwas another colormaybe brown orgray-,at least once earlier in the day.Chameleons are quick-change artists, allright, but they do i't just change color anytime they want to.

Factors that affect a chameleon's in-voluntary color change are temperature,sunlight, nervous stimulation (fear, anger,hunger), and the chameleon's own pig-mentation. In the morning when the air iscool and there is little sunlight, your typicallizard might start its day off a spotted,light brown shade. As the day becomeswarmer and brighter, the chameleon mayturn solid gray brown, making it easier toblend into its environment and sneak upon tasty insects. The chameleon movesvery slowly but can do two things fastchange colors (in 90 seconds) and whiskits lengthy tongue out to snatch its prey(in one-third second).

A chameleon meeting an oncomingchameleon may issue a color threat. Puffedup and bulging, the angry chameleon maydisplay yellow stripes or turn vivid green,even when its surroundings are not. Afight usually ensues; the winner will alwaysbe a brighter color than the loser.

The chameleon also changes color to

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MI=startle its predator, giving itself time toget away. And during courtship, chame-leons display a whole range of colorsfrom yellow, white, and various shadesof gr...:en .to brown and even brick red.

To get an idea of what enables a cha-meleon to change colors, you must knowabout its skin layers and pigmentation.For a better understanding, hold out onehand and spread your fingers apart. Now

'put the other hand directly under this one,spread the fingers and Writ' your lowerhand so the top and bottom fingers cross,forming a grid. Think of the top hand asa layer of skin containing only blue pigmentcells. The lower hand is a skin layer ofyellow cells.

Below your two hands, picture saclikecells which have long tendrils extendingup through the space between your fingers(which is like space between tissue cells)and embedding in the top layer of bluecells. These saclike cells arernelanophoreS,.containing tiny granules of dark pigment.

Sometimes a chameleon's granules willcollect in the cell sacs so tightly that theywon't change the lizard's skin color at all.That's when you see the yellow and bluelayers of skin close together. The effectis green. (The sensations of anger or fearmight be causing the chameleon's granulesto bunch together.)

Sometimes the granules will spread outin the cell sac only. The effect is brownishgreen. (The light, temperature, and mois-ture as well as a placid mood may be thecauses.)

Sometimes the granules may spread into-one or more tendrils and mask some ormost of the yellow color in the lower skinlayer, resulting in shades of Wish broWn,brown, black, or stripes and spots..

Also, in the chameleon, red cells movethroughout the skin layers, sometimesadding still other effects.

'Other color- changers.Chameleons are not the only animals thatchange color: The octopi's is another quick-change artist. Normal:), a dull shade ofgray, a frightened, angry, or excited oc-

INSTRUCTOR. January 1983 81

NATURAL WONDER continued

topus may turn a deep rose, orange, red,or purple. Small bags of pigment cells inthe animal's skin are connected to its ner-vous system. The bags expand or contract,depending on the octopus's emotional state.Changing to a bright color startles predatorsand allows an octopus to make a quickgetaway.

The flounder is another color-changer.This saltwater flatfish lives on the bottomsof bays and along the shores of most seas.It has a flattened body with an 'undersidethat is almost white. By reflecting light,the flounder's upper side changes colorto match the .bottom of the sea or bay.This enables it to lie unseen by the shrimpand small fish it captures for food.

Let's talkI. Think about the chameleon and theflounder. Why is color change importantto them? (Color changes enable them toblend into the environment. This helpsthem hide from enemies and ambush vic-tims.for food. In sonic cases, bright colorchanges in the chameleon are importantfor courtship because they attract mates.)2. The squid is a sea animal that is similarto the octopus. Like the octopus, when asquid is frightened, it turns a bright shadeof red. Why is this a good color to turn?(The sudden brightness startles predatorsand r.slows the octopus or squid to makea quick escape.)3. The hippolyte is a small relative of theshrimp. A very young hippolyte can turngreen, brown, violet, yellow, orange, orred within a 10-minute period. But an adulthippolyte is likely to require 24 hours tocomplete a color change. Why are theadults so much slower? (Young hippolytesget more practice! Adults are larger andbetter able to defend t!' emselves from pred-ators without having to change color.)4. What if your own skin could changecolor with your moods? What color wouldyou become to express ,anger? Sadnes0Happiness? Boredom? (Answers will vary.)

Let's investigateI. Students can make their Own paperchameleons and explore how this animalmakes quick color changes. First, haveeach student draw a chameleon on blackconstruction paper and cut -it out. The shapeshould include key features like turret eyes,a prehensile (handlik,,:) tail, and grippinglegs. Next, cut an oval.in the middle ofthe body. Give each student a piece ofyellow, red, green, blue, and black tissue,each large enough to cover the oval.

82 .^4STRuCTOR. Jaruary 1983

Now, for a quick change, tell studentsto paperclip different combinations of tis-sues over the body opening. They can sechow different-colored tissues mix to formother shades, tones, or colors.

Let's write ,

1. Pet-store owners often confuse the cha-ineleon with another small lizard, calledthe anole. They are closely related, butthere are important, differences betweenthem. Use reference books to find out howthey are alike and how they differ. In -ashort report, explain how a pet owner couldtell a chameleon froin an anole. (The anolemoves much faster than the chameleonand has a longer, more slender body. Also,chameleons cling to tree branches withtheir tails, while anoles use their stickyfootpads.)2. The fiddler crab is another color- chang-er. Use reference books to find out whatcolors this animal displays and under whatconditions. Then write a diary entry abouta day in the life of aliddler crab. Mentionat least three different events that causedcolor changes. (Fiddler crabs are red whenexcited or frightened, dark reddish brownwith purple hues when angry, and lightbrown under normal conditions.)3. When you blush, your face undergoesa quick color change. Find out what hap-

. pens in your body to cause this: (Blushingresults from stimulation of the vasodilatornerves, located in tiny blood vessels nearthe surface of the skin, known as capil-laries. When the vasodilator nerves arestimulated, they cause the capillaries toswell with blood. As a result, your facereddens and becomes warm.)

Now describe something that happenedto you which really made you blush!

BibliographyCarthy, John D. Animal Camouflage.

McGraw-Hill, 1974.Carrick, Carol. Octopus. A Clarion Book/

Seabury Press, 1978.Cook, Joseph J., and William L. Wisner.

The Phantom World of the Octopt..... and

Squid. Dodd, Mc,:d & Co., 1965Hellman, Hal. Definse Mechanisms.

from Virus to Man. Holt, Rinehartand Winston, 1969.

Hess, Lilo. The Remarkable Chameleon.Charles Scribner's Sons, 1963.

White, William, Jr. The American Cha-meleon. Sterling Nature Series, 1977. 0

Sandra Markle is INSTRUCTOR'S scienceconsultant. She teaches science in theclassroom and on TY.

1 ' 1 1 I, 1 1

"agara Fallsand other super waterfalls

Sandra Markle,0

Is it true that Niagara Falls is shrinking?What makes a waterfall fall?' In thismonth's Natural Wonder Notebook, sci-ence consultant Sandra Markle will explorethe answers to these and other mysteriesabout powerful waterfalls. Also includedare brain;stretching discussion questions,an activity that simulates how NiagaraFalls was formed, and three challengingwriting assignments. Sandra believes that"when students are asked to talk over,investigate, and then write on a scientificphenomenon, they really begin to learnwhat Ft's all about."

You 'may want to expand your study ofwaterfalls by having kids set up a Natural}'fonder Corner in your room, completewith magazines, posters, and bulletinboards. Start by clipping and posting theminiposter of Niagara's Horseshoe Fallsat left. Enlist your librarian or media spe-cialist's help in finding other materialsand check the bibliography at the end ofthis feature.

When the month's over, store your mini-poster and activity information in a ringednotebook for easy reference. Then primeyour students for March's featureand anew corneron elephants' trunks andother nifty sniffers! This series will con-vince your kids that natural wonders areeven more wonderful when you begin toexplore them.

Each second during the day, 700,000 gal-lons of water plunge over the rim of NiagaraFalls. That's enough water to wash 23,333loads of clothes, fill 4,000 bathtubs, orflush 140,000 toilets! These thunderingwaters form the most powerfutfalls in theUnited States and 'the third'mightiest inthe world.Why Niagara falls

Some-waterfalls are formed overnight.For example, during an earthquake in 1959,plates in the earth shifted and caused theland around Hegben Lake in Montana todrop sharply. Now, previously smooth-running streams pour down several rockywaterfalls.

Other falls, like Niagara, were createdthrough centuries of erosion. About 12,000years ago when the last ice age ended, amelting ice sheet caused Lake Erie to ov-erflow. The overflow formed the NiagaraRiver, which began to run north towardLike Ontario. The force of its movingwater and the scouring action of the gravelthat was carried with it widened and deep-ened the river channel. But then the riverreached an area of land made of hard do-limite rock (compact limestone). This rockcap was 80 feet thick and virtually erosion-resistant, and so the river flowed over therock cap without cutting through muchrock.

Beyond the cap, however, the land wasmade of soft layers of limestone, sandstone,and shale, and so once again the river wasable to erode the earth. Eventually, theriver's activity formed a steep, canyonlikegorge with the rock cap as the gorge'shighest point and the bed of softer earthbelow it sinking lower and lower. Thatgorge became Niagara Falls. Today Ni-agara Falls forms a boundary line for Can-ada and the L'.-iited States.Breaking away

Niagara is actually two falls separatedby Goat Island. The crescent-shaped Horse-shoe Falls (on the Canadian side) is 185feel high and 2,600 feet wide. The Amer-ican Falls (on the U.S. side) is. 190 feethigh and about 1,000 feet wide. Rock slide,gradually have changed the.appearance ofNiagara Falls through the years. Churningwaters at the base of the falls eat awaythe soft underlying rock layers, causingthe unsupported hard rock on top to breakoff. (See diagram.) Most of this erosionoccurs on-Horseshoe Falls because morethan 90 percent of the Niagara. RiVeyplunges over it. On the average, HorseshoeFalls shrinks back toward Lake Erie at arate of about three feet each year. TheAmerican Falls loses four to six inches ayear.

Because Niagara Falls is an importantsource of hydroefectrie power and becauseit's a tourist attraction, in the 1960s, people

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became concerned about the crumblingrock cap. In 1969, the Army Corps ofEngineers built a dam to temporarily shutoff the American Falls. Workers then ce-mented seriously eroding areas on the falls.During the project, the engineers were ableto estimate the amount of money and effortit would take to make a major reinforce-ment of the falls and decided it would betoo expensive.

Waterflovi1111am* 11111111 IMIO 'Ili::1.111111111 Ma Onmar

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Hard limestonelayers

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So if you're planning to see NiagaraFalls, don't wait too long. \Waterfalls don'tlast forever. Geologists estimate that Ni-agara will probably only f ll for another

22,800 years.Falling power

Hydroelectric stations use the force ofmoving water to produce electricity. Thereare three such stations at Niagara Falls.One is the Robert Moses plant, which isthe largest hydroelectric generating stationin the eastern United States and one ofthe largest in the world. The two Sir AdamBeck plants on the Canadian side aresmaller but also use the fails to producea great deal of electricity.

A treaty between the United States andCanada stip'ulates that 100,000 cubic feetof water would be allowed to flow overthe falls in the daytime and 50,000 cubicfeet could flow at night. This water is forpeople to watch, Before the rest of thewater reaches toe falls, it is directedthrough descending tunnels and canals thateventually lead to turbines. The moving

INSTRUCTOR. Fwaruary 1983 111

112 ,NSTRUCTOP Fetruary !983

NIAGARA FALLS continued

water turns the turbines, which turn gen-erators which produce electricity.Other super falls

At an average height of 182 feet, Niagarais not tall compared to other falls. But theamount of water that pours over it makesit a powerful one. It is a drainage outletfor the four upper.Great LakesSuperior,Michigan, Huron. and Eric. And morethan a million springs pour into those lakes!

For information on other powerful falls,see the chart at the bottom of this page.Angel Falls (2,648 feet) in Venezuela isthe highest waterfall in the world, andRibbon Falls (1,612 feet) in California ishe highest waterfall in the United States,but neither has water flows as powerfulas the falls in the chart.

Let's talkI. American Indians lived in the NiagaraFalls area long before the first Europeansarrived. The name Niagara comes fromthe Iroquois word Onguiaahra meaningthe strait. Why is Niagara a good namefor this falls and river? (A strait is a narrowpassageway that connects two large bodiesof water. Niagara Falls and the NiagaraRiver are situated between Lakes Erie andOntario.)2. Explain why there is often a rainbowover Niagara and other waterfalls. Howcould you make your own rainbow? Hint:Start by finding out what causes rainbows.Check reference books. (When light passesthrough water, it refractsbends. Whenthis happens, it spreads out the differentcolors that make a light ray. Sprayingwater into sunlight will create the sameeffect as a rainbow above Niagara Falls.)3. Why are only a few of the world'sbiggest falls used to generate hydroelectricpower? (Most of the world's biggest fallsare located in rough, inaccessible areasthat make the construction of a generating

station difficult. Also, some of the highestfalls don't have as much water flow assome of the lower falls. Heavy water flowis needed for hydroelectric power.)

Let's investigateI. Your students can see for themselveshow Niagara Falls was formed. Dividethem into teams of five or six students.Give each team a fairly large cardboardbox, a bag of soil, and a three- tofour-inch piece of foam meat tray.

First, have students pack down a two -inch layer of dirt, then another two-inchlayer, and another. Now place the pieceof meat tray on the dirt, about four inchesfrom one end of the box. Pack down an-other two inches of soil.

Starting from the end of the box wherethe meat tray is buried, tell students touse their fingers, a pencil, or a spoon toimitate the movement of rapidly flowingwater and carve a river channel. (Do notuse water to do this. It will destroy thebox.) The river can cure and meanderfrom one side to the other, cutting deeperand deeper into the earth. When kids reachthe foam chutik, they should leave thechannel at the level of the chunk. Past thechunk, 'they should continue to dig thechannel deeper.

Gradually, the waterfall will take shape.Encourage students to erode layers of softsoil that lie under the resistant foam layer,just the way churning water at the bottomof Niagara Falls does. Children shouldeven break off pieces of foam to dem-onstrate how Niagara Falls is slowlyretreating.

Let's writeI. Louis Hennepin, a Roman Catholicpriest who traveled with the French ex-plorer Robert de La Salle, left us the firstwritten account of Niagara Falls. In a blok

Powerful waterfalls

Waterfall RiverAverage Water Flow

Over the Falls Average Height

Guaira Kiruna 470 cubic ft. per scc. 213 ft..(Brazil-Faraguay)

Knonc Mekong 410 cubic ft. per scc. 70 ft.(Cambodia-Laos) C

Niagara . Niagara. 212 cubic ft. per scc. 182 ft.(Canada-United States)

Grande Uruguay 106 cubic ft. per sec. 75 ft.(Argentina-Uruguay)

'NIAGARA FALLS ronauted

published in 1683, he wrote: "The' waters

foam and boil in a few, fill miiner. Theythunder continually. It's been 300 yearssince Hennepin viewed Niagara Falls. Heprobably would appreciate an update fromyou. In three or four paragraphs, describethe falls today: How is it the same? Howis it different? (Even though Niagara Fallshas moved a few miles closer to Lake Eriedue to erosion, in many respects, the gorgeand its thundering waters remain the same.Its surroundings. however, are a differentstory. There now are hydroelectric plants.factories, large buildings. and many. tourists.2. In the 1880s, people feared the rapiddevelopment of tourism and industry wouldruin the scenic beauty of the area. Theypleaded with government officials fromboth Canada and the United States to help.Around 1885, both countries establishedlarge park areas where factories and touristhotels could not be built. The parks remaintoday. Pretend you are back in the 1880s.Are you for or against more commercialand industrial development? Take a stand.then write kletter to a government officialin which you convincingly explain yourposition. (Answers will vary, of course.Encourage students to be persuasive andto use proper letter-writing format.)3. Many groups of North American Indiansenjoyed telling imaginative stories aboutnature such as why the bear has a shorttail and why we have night and day. Thesetalcs are called legends. Write a legendabout hciw Niagara. Falls was formed. (Ifstudents have difficulty with this assign-ment, read them a few tales from The LongTailed Bear and Other Indian Legends,Natalia M. Belting, Bobbs Merrill, 1961.)

BibliographyBooks about Niagara and other falls aredifficult to locate. The best and most ac-cessible information can be found in oldNational Geographic magazines. Showstudents how to use the Reader's Guidein their library. Then have them locatesome of these, magazine articles onwaterfalls.

Because Niagara Falls is a tourist at-traction. travel agents often have pamphletson it. See if you can collect a few. Theyare always fun to read.

To find out more about hydroelectricpower. read Water Over the Dam by Dor-othy C. Hogner. Lippincott. 1960, grades7-9.

Sandra Markle is Issraucrows scienceconsultant. She teaches science in theclassroom and on television.

INSTRUCTOR, rebtuafy 1983 p. //..3

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I r I 1bPo I I

Elephants' trunksand otter nifty sniffers

This month we're going to investigate a,topic that ids can really polc t their nosesinto:eleph s' trunks and other niftysniffers! Inclu in this teaching unit arefascinating quest s to discuss, activities'that experiment wi our sense of smell,and three challenging w assignments.

Expand your study of noses by ,settingup a Natural Wonder Corner in your room,Complete with reference books, pictureslike the miniposter at left, and a few self-directed activities that invite students tobecome scent detectives. Here's one suchactivity: Cut squares from an old towelor sheet. Saturate each with a familiarscent: lemon 'juice, orange juice, applejuice, onion juice, ammonia, cinnamon,and so forth. The: each square into aseparate baby food jar and seal with alid. To examine each scent, your studentsshould take off the lid and sniff. Wheneveryone has had a chance to guess andwonder, you cati".reveal the scents.

Adorn your center with a bulletin boardfull of noses: a pig's snout, a rabbit'swiggly nose, an anteater's long nose, andmore. Or encourage students to bring inpictures of famous noses: Snoopy's, BobHope's, Piesident Reagan's, Karl Mal-den's, Barbra Streisand' s, Miss Piggy's.

Does an elephant snore? You bet. Andwhat a snore it makes through a nose thatcan be up to six feet long!

The baby giant in the picture at left isjust getting the hang of what to do withits trunk. It takes six months for a babyelephant to learn to handle its nose well.

Actually a combination of upper lip andnose, the trunk is a super sniffer. With it,the elephant can sniff out food and Waterin several directions without even turningits head.

Elephants eat at least 16 hours a day,stopping only to find another lunch spotor to take a short nap, so a good snifferis important. The elephant's trunk is alsoa goad food gatherer. The soft, fingerlike .projection on the end of the trunk lets theelephant pick up even small leaves or fruitas easily as you could with your fingers.

Stretching its trunk high into a tree, anelephant can also collect food that shortergrazers miss.

In fact, in its hurry to pluck a mouthful,an elephant may rip off a big branch. Butthat's no problem fcr the elephant. Madeup of more than 40,000 muscles, its trunkcan lift a 600-pound load.

As you may have guessed, we're nottalking about a lightweight eater. The el-ephant, which can be as tall as 11 feetand as heavy as 14,000 pounds, eats 300to 600 pounds of vegetation a day.

An, elephant is also a big drinker-30to 40 gallons a day. Slurping up a gallonand a half in each sniff, the elephant squirtsthe water down its throat. Elephants lovewater. They use their trunks to spray itacross their ears and backs to cool them-selves. They even enjoy swimming. Andwhen the water is deep, they use theirtrunks as snorkels. Good grooming for anelephant is a bath, followed by a roll inthe mud. This is finished off by a dustingof dirt which the elephant sprays over itselfwith its trunk.

An elephant's trunk is a hand, a hose,and a super sniffer. But it's more:Anelephant trumpets, squeals, and screamsthrough its nose. Fighting bulls (male el-ephants) lock trunks in a tug-of-war-topull each other off balance. Mother' ele-phants caress their babies with their truaks.They correct a naughty child with a swift,noisy spank. A baby elephant follows theherd by gripping an adult's tail with itstrunk. And when these giants really likeeach other, they twist their trunks togetherin a big elephant kiss.

Other nifty sniffersElephants are not the only animals withuseful noses. Bats use their noses to helpfind their way through the dark by blowinggreat bursts of sound from them. The bat'ssensitive ears pick up the echoes as theybounce back. Bats can nose in on a flyinginsect up to 15 feet away.

Then there's the shark. Its gills takecare of supplying needed air. Its nose_ is

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strictly for smelling. Each nostril is linedwith a smell-sensitive membrane. Mes-sages pass directly from the nose to thebrain. A shark can.smell blood in the waterone-fourth mile away.

The elephant, the bat, and the shark arejust three of many animals with specialnoses. The activities that follow will ex-plore these and ottkei: nifty sniffers morethoroughly.

Let's talkHere are a few thought-provoking ques-

tions to discuss with students.I. Moles are animals that live deep un-derground. The star-nosed mole has 22fleshy tentacles forming a ring around itsnostrils. The top middle two are heldridgedly forward. The rest wiggle con-stantly as the mole searches for insects toeat. Like the elephant, this animal has avery sensitive nos and an excellent senseof smell. Why is the mole's nose its mostimportant sense organ? (Because moleslive in the quiet, dark depths, they don'tneed a good sense of hearing or sight asmuch as they need a nose for sniffing andfeeling their way around.)2. Some ecologists think elephant herdsshould be thinned (some of the animalskilled) yearly. They say that large herdsare too destructive to the environment.Other ecologists say the herds should beleft alone. Nature should be allowed totake its course. What do you think? (An-swers will vary.)3. An elephant uses its sense of smell toknow if something is good to eat. Howdoes your nose help protect you? (In gen-eral, food that iilsafe to eat smells good.Bad-smelling food such as spoiled meatis dangerous to put in your mouth.)

Let's investigateI. Can you taste what you can't smell?Students can discover the answer forthemselves. Give each student a paper platewith a tiny piece of apple and a tiny pieceof onion. Ask them to close their eyes.Then tell them to turn the plates around

INSTRUCTOR. March 1963 77

NATURAL WONDER continued

until they ap,n longer sure where thetwo pieces of food arc located.

Now, have .students pinch their nosesand place one piece of food on theirtongues. They'll find that without beingable to smell, the foods won't have a verydistinctive flavorThough they still cantaste it. As a class, talk about how. foodslack a lot of flavor when someone has astuffed-up nose. Generally, we taste andsmell food at about the same time.

Let's writeBelow are three writing assignments kids

will enjoy.I. All dogs have better smell sensors thanpeople do. Bloodhounds are the champs.'And their sad-looking faces help them.Their droopy ears stir up, scents from theground. Their wrinkled skin traps thescents.

When a seven-year-old boy became lostin eastern Washington, a bloodhound wasused to help find him. After sniffing anarticle of clothing that the boy had worn,the dog was able to follow the child'sbody scent. In less than a day, the blood-hound found the boy. Find out more abouthow dogs are used to find lost people.Write a newspaper account about one 'ofthese real dog-detective incidents. (An-swers will vary.)2. Read "The Elephant's Child" (Just SoStories, Doubleday, 1972) by RudyardKipling. Then make up a story of yourown about how the elephant got such along nose. (Answers will vary.)3. What if your nose were as long and asuseful as an elephant's trunk? Write a fewparagraphs about the things you wouldenjoy being able to do with your nose.(Answers will vary.) 0

°BibliographyBarner, Bob. Elephant Facts. Unicorn

Books, E.P. Dutton, 1979.Elephants and Other Land Giants. Time-

Life, 1976.Holbrook, John. A Closer Look At Ele-

phants. Franklin Watts, 1977.Van Gelder, Dr. Richard. Whose Nose Is

This? Walker and Company, 1974.Williams, Barbara. Seven True Elephant

Stories. Hastings, 1977.Zappler, Lisbeth. The Natural History of

the Nose. Doubleday and Company,Inc., 1976. 0

Sandra Markle is INSTRUCTOR'S scienceconsultant. She teaches science in theclassroom.and on television.

78 'NSTouCTOP 'tare~ '983

MOW

I I I I '

Tornadoesand other big winds

Sandra Markle

Hold onto your hats! This month the Nat-ural Wonder Notebook explores tornadoesand other big winds.

Set the stage for some gusty discussionsby turning your Natural Wonder Cornerinto a multimedia storm center completewith tornado sound effects, maps, andmoving pictures. Tape the song "TornadoMusic" from the Broadway musical, TheWiz, and the classical piece, "A Nighton Bald Mountain" by Modest PetrovichMoussorgsky. Play these and ask studentsto explain how the music portrays a storm.(It builds, becomes faster, and grows moreviolent.) Challenge students to make flipbooks (a set of pictures that capthre eachmovement of an activity) of a storm buildingand a tornado forming. (Most encyclo-pedias can provide model illustrations.)When the artwork is complete, replay themusic as kids flip through their books.Now you have tornado movies!

To decorate your corner this month,cover a bulletin board with a map of theUnited States, marking the states in Tor-nado Alley (Kansas, Iowa, Nebraska,Oklahoma, Missouri, South Dakota, andMinnesota) with small, black funnel clouds.Under the map, point an arrow towardthe southwest corner of your classroom.This designates the direction most tor-nadoes come from.

Have each student cut a spiral (cutcounterclockwise, the way real tornadoeswhirl) from a piece of black constructionpaper. Then hang up these minitwistersand launch yodr own Operation Skywarnas you begin to investigate tornadoes andother big winds. (The real Operation Sky-warn is network of volunteers who watchfor the appearance of a tornado after anofficial Tornado Watch is issued.)

And, of course, don't forget to post thecolorful twister at left!

"Like the noise of 10,000 freighttrains!" one eyewitness said. "Like thebuzz of a million bees!" said another.Both persons were describing the soundof a tornado that had passed over their

heads. Meteorologists (people who studythe weather) believe that the sound a tor-nado makes is caused by the almost con-stant lightning that laces through the insideof the funnel cloud. Tornadoes are thesmallest and yet the most destructive ofall storms.

A tornado's funnel is rarely more than350 yards across. (You could walk thatdistance in 350 long steps.) Some are nowider than a two-lane road. And when atornado touches the ground, it lingers onlya half minute before whirling on.

So what can a little piece of wind doin 30 seconds? A tornado can uproot trees,blow a house apart, carry away a bridge,throw cars across a parking lot, and performa lot of other very destructive acts. Thesesuper storms have wind speeds measuredat 150 to 300 mph and estimated (basedon damage done) at up to 800 mph. Thcrcare many things about tornadoes that me-teorologists don't know because thesestorms are too dangerous to study up close.But meteorologists do have a pretty goodidea how tornadoes form.

When land or water is heated by thesun, the air above it is warmed. The warmair rises. (Watch the steam coming out ofa teakettle.) Cooler air then rushes in tofill the space vacated by the warm air,and this moving cooler air becomes wind.The faster the warm air rises, the strongerthe cool winds become.

Usually when a mass of hot, moist airmeets a cold, dry mass of air, the cool airpushes under the warm air. But sometimesthe cool air settles on top of the warm air,trapping it. The warm air struggles upward,and if a "tongue" of warm air breaksthrough, it cuts a tunnel into the cold airmass. Warm air quickly rushes in, forminga strong updraft. Now, still more air sweepsin from all sides to fill the spaces leftvacant by the upward surging warm air.partly due to the earth's own spinning andpartly for reasons as yet unknown, a me-socyclone (a rotating column of air) forms.Soon the rising warm, moist air cools, andwhat once was water vapor ch gn intop

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water droplets, forming a visible cloudaround the updraft. This funnel-shapedcloud is pictured in the photograph at left.

Tornadoes form inside thunderstorms.The twisters usually move from the south-west to the northeast across the U.S.,,bc-cause this is the dircction of the prevailingwinds (general pattern of winds). Tor-nadoes rarely last longer than 20 minutesand seldom travel farther than 16 milesbefore they die. A tornado's path is usuallya skipping course, touching down and thenleaping on before touching down again.A record tornado did cut a path of de-struction 293 miles long from Mattoon.Illinois, to the eastern boundary of JenningsCounty, Indiana, on May 26, 1917.

Wherever tornadoes reach the ground,they cause disaster. In a 24-hour periodon April 3and 4 in 1974, 148 tornadoesstruck 13 states and parts of Canada. Thiswas a record outbreak with a death toll of315 people. Hardest hit was Xenia. Ohio,which lost two percent of its populationand had whole sections of houses andbuildings leveled.

Many tornado-related deaths are causedby collapsing buildings. Besides the terribleforce of the wind, the rapid rush of airinto the funnel creates a partial vacuumaround the tornado. The sudden removalof the equalizing pressure of. air on theoutside of a building makes the air insidethe building push out. The building thenexplodes.

Tornadoes are a worldwide wonder, butthe U.S. has the most twisters of anycountrymore than 620 a year. The ma-jority of them strike the central states bee.-tween the Rocky Mountains and the Ap-palachian Mountains. Called TornadoAlley, this region is a battleground wherewarm, moist air from the Gulf of Mexicoand cold, dry air fromoCanada meet headon. April, May, and June are the monthswhen these air rnasses are the most differentAnd therefore \ most likely to generatetornadocs.

Fortunately, the death toll from torna-does has decreased sharply since the late

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NATURAL WONDER continued1950s. This decline is mainly due to thedevelopment of new storm detection tech-niques (weather satellites and improvedradar) and to the creation of the NationalSevere Storm Forecast Center. This centeris located in Kansas City, MissourirightIn the middle of Tornado Alley. OperationSkywarn, a national network of local vol-unteers, also plays an important role intornado detection because tornadoes canappear suddenly and without warning, de-spite the many efforts to forecast their

approach.Forecasters issue different kinds of tor-

nado bulletins. When they issue a TornadoWatch, it simply means that condition'sare right for a tornado to form., Peopleshould proceed as usual but stay tuned forupdated reports. When a Tornado Alert isissued, that means a tornado has beenspotted, and anyone within the storm'sprojected path should take immediate safetyprecautions. If you are out walking whenyou are warned of a Tornado Alert, youshould go to the nearest steel and concretebuilding (always remain away from win-dows). If a building isn't close, lie downin a ditch and cover your head. At home,you should go to the basement and getunder a heavy table. If you don't have abasement, move to the center of the houseand take shelter under heavy furniture. Atschool, you should move to interior hallson the building's lowest level. If you'rein a car, the driver should drive away fromthe storm. (Always move away from atornado in right angles to allow.. for thetwister's curved path.)Or if the storm isvery close, you should leave the car andlie down in a ditch with your head covered.

Tornadoes will never become less dan-gerous. But thanks to high-powcr tech-nology and dedicated storm watchers, weare better able to protect ourselves fromthese super winds than ever before.

,Other big windsTornadoes are not the only winds that

cause problems.' Hurricanes have windsthat average 100-175 mph' and are thelargest storms in the world. Hurricanescan be hundreds of miles wide, travelthousands of miles, and last more than aweek before they die. These storm giantsform over the oceans near the equator andspiral toward land. Brave hurricane huntersfly into these storms to gather informationabout wind speeds and dircction and tomap the size of the storm.

And then there are blizzards. Blizzardsare winter storms that happen when super

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cold, polar air crashes into warm air thatis full of water vapor. As the polar airshoves the warm air up into cooler tem-peratures, the water vapor freezes and be-comes snow. Fierce winds and very coldtemperatures come with the snow, In thewinter of 1976-77, blizzards brought snowto southern states unaccustomed to winterstorms. Heavy snowfalls in northern statesleft communities isolated, without powerand without heat until the storm had endedand people could begin to dig out.

Tornadoes, hurricanes, and blizzards arejust three kinds of winds, The activitiesthat follow will explore these and otherwinds more thoroughly.

Let's talkShare these discussion starters with the

class.

I. When the ground overheats, the layerof air above it gets warm and rises rapidly.Cooler air rushing in to fill this space ofjenforms a whirlwind (a minitornado).Whirlwinds and dust devils (dust whirledby the whirlwinds) are most frequent indeserts, but dust devils are also commonin big cities. .Why? (Cement- and pave-ment-covered areas collect heat, then ra-diate it into the air. Tall buildings channelthe rising air upward, creating strongupdraft as cool air rushes in underneaththe rising warm air. Dust from constructionis whirled in this updraft.)2. Project Stormfury, undcr the control ofthe National Oceanic and AtmosphericAdministration, was set up to study waysto stop hurricanes. These scientists wouldlike to try out their ideas, some of whichinvolve seeding and exploding clouds. Sofar they have been allowed to experimentonly on a very few hurricanes that werefar out at sea. People arb afraid that suchexperimentation may, in fact, make thestorms worse. Do you think scientistsshould be allowed to experiment wish hur-ricanes? (Answers will vary.)

Let's investigateI. Students can see for themselves thatair rises when it's heated. Use an electricskillet as a heat source. Place a glass popbottle (one without cracks) in the skillet.Cover the top of the bottle with the neckof a large rubber bailor. Pour enoughwater into the skillet to cover the bottbm,and turn tie skillet on medium heat. Beprepared to add more water as needed.

As the air in the bottle heats, studentswill see the balloon till and lift. Now,have the class predict what will happen

as the air in the bottle cools. Cool airsinks. Watching the cooling bottle willprove this and show why cold air massesusually move under warm air masses.2, To demonstrate why tornadoes makebuildings collapse, place an empty, well:washed metal can (the kind duplicatingfluid comes in) in the electric skillet. Re-move the cap. Pour enough watt nto theskillet to cover the pan bottom. Heat onmedium heat for 20 minutes, adding morewater as needed. Quickly screw the caponto the can. Use a potholder to removethe can from the heat.

Tell your students that heating causedthe air in the can to rise and escape throughthe opening; capping the can preventedenough cooler air from rushing in to nilthe can. There is now a partial vacuum inthe can. As your students watch, the canwill begin to collapse. This is the reverseof what happens to buildings during a tor-nado. The air around the can is pressingin (IS pounds per square inch). In a build-ing, the air is pressing out.(Note: These two investigations are de-signed for teachers to perform only.)

Let's writeHere are two writing assignments studentswill enjoy.I. Members of the U.S. Air Force'sWeather Reconnaissance Squadrons arehurricane hunters. Do a little research onthese operations. Then pretend you are ahurricane hunter and write a diary accountof a flight into a hurricane.2. Use the index for a major newspapersuch as the New York Times or the ChicagoTribune to look up articles about tomadoes.Two recent major outbreaks are the onesoccurring on April 3-4, 1974 and the PalmSunday outbreak on April 11-12, 1965.Then write your own fictional account ofa tornado outbreak.

BibliographyBixby, William. Hurricanes. DavidMcKay Company, Inc., 1979.

'Compton, Grant. What does a Meteo-rologist Do? Dodd, Mead & Company,1981.Hitte,° Kathryn. Hurricanes, Tornadoes,and Blizzards. Random House, 1960.Irving, Robert. Hurricanes andTwisters.Alfred A. Knopf, 1955.Ross, Frank, Jr. Storms and Man. Lothrop,Lee &'Shepard, 1971.

Sandra Markle is INsraucroa's scienceconsultant. She teaches science in theclassroom and on television:

II/RURAL WONDER NOTEBOOK Number '5 In n series:

The Grand Canyopand other holes in the ground

Sandra Markle

Visited by more than three million touristsannually, the Grand Canyon is The naturalwonder people most want to see in theUnited States. This month's Natural Won-der Notebook features nit o ne, but threeGrand Canyon adventures: one on foot,one by burro, and one by boat. Each pre-tend trip offers a different perspective ofa truly grand canyon.

Turn your Natural Wonder Corner intoexpedition headquarters by displaying alarge map of the area. Using the map onthe following page as a model, mark theorigins of the first two journeys, whichare down canyon walls. Use two differentcolors of ink. In a third color, trace theentire route of the last journey. along theColorado River. Hang up pictures of thecanyon, including the miniposter at left,and stock your corner with books on wil-derness survival and canyon expeditions.(See bibliography.)

A canyon is a valley with two steep sides.The Grand Canyon extends 277 miles htnorthwest Arizona, is more than'a miledeep, and ranges from 2 to 18 miles wide.The Colorado River flows through itsvalley.

Millions of years ago the entire areawas a flat plain, situated just above teAlevel, and the Colorado River was a mean-dering stream. Then, active forces insidethe earth uplifted the plain and sent theColorado River rushing toward the sea.As the river grew larger and more powerful,it picked up heavy loads of gravel; silt,and sand, which scoured a deep paththrough the canyon. Down, down the Col-orado River, sliced, uncovering layers ofrock that had been deposited by water andwind millions and even billions of yearsearlier. You'll have a chance to explorethese layers of rock carefully on the firstGrand Canyon adventure --the trip on foot.On foot This two-day trip requires the mostendurance and preparation of the three ad-ventures. You'll want to wear comfortableshoes and clothing that can be shed oradded in layers as needed. Park rangers.

recommend that each person carry twogallons of drinking water and enough foodfor meals, including a supply of high-energy food like nuts and raisins. .

Find Kaibab :Trail on your NaturalWonder map. It is located on the northside of the canyon (8,000 feet above sealevel). This is where your hike -begins.The trail is approximately 21 miles. Onthe first day, you'll climb down the northwall from rim to river. At the bottom ofthe canyon is Phantom Ranch, where youcan rent a cabin for the night. The nextday you'll climb up the south wall andout et the canyon. This hike is ideal forexploring the Grand Canyon's many layersof rock. (See illustration on this page.)

As your.. trip begins, you'll notice thata thin coat of topsoil covers the north rim.Below this lie the Kaibab and Toroweaplimestone forMations, which are about 225million years oldyoung compared tolower formations. Look for fossils (rem-nants or impressions left by plants andanimals) in these limestone layers. Imprintsof tri-lobites, sharks, corals, and shellfishare frequently found. But those arc seacreatures, you say! Well, like the olderlimestone formations you'll encounterfurther down, Kaibab and Toroweap provethat this area was covered by ocean atvarious times.

The next layer you reach is CoconinoSandstone. It's about 300 feet thick and

Odicates that the Grand Canyon was oncea desert. Coconino was the top layer ofrock. (Sandstone is formed by compressingsand dunes.) Look for fossils of scorpions,spiders, and small desert reptiles here.

Your next stop is Hermit Shale. Shalelayers record periods millions of years agowhen mighty rivers dumped sediment overthe Grand Canyon area. Careful inspectionof the shale can sometimes reveal animaltracks.

Descending further, you reach severallayers of limestone (Suapai Formation,Redwall Limestone, Temple Butte Lime-stone, and Muav Limestone) and then Ta-peats Sandstone.

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The tilted layers below the TapeatsSandstone formatipn arc called the GrandCanyon Series. This rock formation is half*illion years old and represents a timewhen the land was uplifted, broken intomountains, and then eroded flat. The onlyfossil record of life in this formation isalgae, a primitive plant related to seaweed.

The basement rocks are worth the entirewalk. Called Vishnu Schist, these medium-and coarse-grained black rocks are esti-mated to be 1.3 billion years old sonicof the oldest rocks visible on earth. Thereis no evidence of life shown in this for-mation, but then these rocks have beengreatly changed by pressure froni the manyrock layers resting above them and fromheat within the earth's crust.

You've made it! You've reached thebottom of the Grand Canyon. Look up atthe rim of the canyon: that's one mile up!Enjoy the valley, the view, and your stayat Phantom Ranch, but don't linger long.The forces that carved this deep canyonare still at work. In a million years or so,the climb up the south rim will be muchhigher!By,burro Find Bright Angel Trail on theexpedition map. Located on the south rim,the narrow, winding trail descends for eightmiles into Granite Gorge. You'll followit to the canyon floor and back. Mountyour burro, hang onto the saddle horn,and enjoy the view as your surefooted packaninial plods along the rocky trailbutdon't lean over too far. The trail may bewinding, but it's still very steep!

10INSTRUCTOR. May 1983 49

-NATURAL-WONDER continued

As you look across the canyon: you see_rounded rock formations. Some look likegiant stepping-stones: others resemblestone towers and fanciful sculptures. Theseshapes are the result of a process calleddifferential erosion: softer rock particlesare carried away by erosion while moreresistant rock remains.

Four eroding forces are at v.:ork,,in theGrand Canyon: running water, frost. wind.and gravity. TI' running water comes fromrainwater. streams. and the ColoradoRiver. As it rushes down or ThrOugh thecanyon. its powerful force loosens rockand carries it away. Some of the waterseeps into the rock cracks. When this waterfreezes, it expands. breaking still morerock chunks loose. Strong winds carryingfine sand blast away other rock particles.Then gravity adds its eroding force bypulling down on jutting ledges until they

The plant life you see along the trail isas varied as the rock sculptures. At thehigher altitudes there is lush vegetation.but as you descend, cactus and yucca ap-pear. That's because the rims of the canyonreceive 16-26 inches of rainfall a year.while the canyon floor receives less than10 inches yearly.

The amount of sunlight that filters intothe canyon also affects plant growth. The'south wall, which you are traveling on,is usually in shadow. Therefore, it supportstrees that need less light like juniper andpinon.. The sunny north rim of the canyonis covered with aspcn, fir, and spruce trees,

The canyon is home to 275 species ofbirds and about 120 other kinds of animals.'Look for beavers, big-horn sheep. elk.lizards, mountain lions, mule deer, an-telope, and snakes. Like the plants, theanimals have settled where the climatesuits their needs. Some like the mule deerrange from rim to river. Others like the

white - tailed Kaibab squirrel are found onlyin one placein-this case, the ponderosapine forest on the north rim:These-squirr._rels, as well as pink rattlesnakes, existonly in the Grand Canyon.

The American Museum of Natural His-tory mounted an expedition in 1937 tosearch this general area for isolated animal.communities. The project was followedwith a lot of excitement as people imaginedall sorts of strange creatures living in theGrand Canyon. One newspaper even sug-gested dinosaurs. No new animal specieswere found; but don't let that stop youfrom imagining what secrets The canyonmay hold as you complete your day-longburro trip.By boat Find Lees Ferry on the map. That'sthe starting point for your last expedition.Lees Ferry was the spot where pioneerscrossed the Colorado River. It's also where.in 1869. John Wesley Powell led 10 menon the very first boat trip through the GrandCanyon.

You are going to board a dory here.The dory, a flat-bottomed boat with. highflaring sides, will take you just past LavaFalls. Depending on .the weather, it willtake you about 18 days to make this 150 -mile trip. From the start, the roar of thewater, is almost deafening, particularly asyou approach Badger Creek and SoapCreek Rapids. These rapids are followedby Hance Rapids, Sockdolger Rapids. andGrapevine Rapids. Rapids are areas in ariver where the current is fast and the river'ssurface is broken by obstructions like fallentrees and rocks. Proceed with cautionthrough these areas. One of Powell's fourboats was shattered against the rocks byrapids.

Look to the left and soon you can spotBright Angel Trail, where you took yourburro ride. Then on to more rapids andfinally, to Vulcan's Throne and Lava Falls.

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50 INSTRUCTOR May 1993 13'

Black lava from an old volcano covers thecanyon walls in this area andrises in cone-shaped figurations (forming a throne) aboveth4.11orth-rim. It is called Vulcan's Throneafter Vulcan, known as the blacksmith ofthe Roman gods. Shafts of jagged lava(some more than 100 feet high) rise fromthe river bed, helping to form treacherousrapids.. Just beyond Vulcan's Throne isLava Fall's, an area of fierce rapids wherethe. river drops 37 feet in 80 yards: Thei-eis no way to portcge (carry the boat around)this falls. The only way forward is to gowith the river.

It took Powell's group three months toreach this point. When the 10 explorerssaw Lava Falls. three elected to' climb upand out of the canyon and begged the othersto come with them. Refusing to give up;POWell and the remaining members climbedinto two boats and launch 4, themselvesinto the rapids,. Today, Lava Falls still haisome of the most powerful navigable rapidsin the world.

Powell's group reached calm watersafely and so will your expedition. In fact.your trip through the canyon is less dan-gerous than the journeys Powell and lateeexplorers faced. Glen Canyon Dam now',controls the amount of water rushing'through the canyon. The flow' may varyfrom 30.000 cubic feet per second to as .

low as 990 cubic feet per seconda mere,trickle.

Other canyonsCanyons form some of the most breath-

taking scenery in North America. Studentsmay wish to investigate Royal Gorge, acanyon in Colorado that supports thehighest suspension bridge; the deep can-yons and thunderous waterfalls formed byYellowstone River in Wyoming; or thebeautiful smaller canyons locatedthroughOut the Canadian Rockies. -Thereare also many underwater canyons calledsubmarine canyons. These are found oncoastal shelf off the mouth of large rivers.One of the largest is at the mouth of theHudson River in New York.

Let's talkPonder these questions with your

students.1. Bryce Canyon in southern Utah wasformed mainly by the eroding forces ofwind and rain rather than by the carvingforce of a river like the Colorado. BryceCanyon is noted for its sharp. exotic rockspires and fragile-looking shapes. Why doyou think this canyon's formations are more

delicate and pointed than the ones foundin the Grand Canyon? (The washing,grinding force of the Colorado Riverrounded off the Grand Canyon'slandscape.)2. When Ebenezer Bryce, a farmer andBryce Canyon'S namesake, was asked whatit was like to live in Bryce Canyon, hereplied, "It's a tough place to lose a cow."What other humorous descriptions mightapply to living in a large canyon? (Answerswill vary.)

Let's investigateStudents can see how differential erosion

'works by placing several large rocks. in abucket and then packing sand around andover the rocks. Gradually pour water (theeroding force) onto the mound. Loose sandpains will wash down to the bottom ofthe bucket. Stop frequently to see how therock formation is changing. More tightlypacked sand and the buried rocks resistthe water's eroding action.

Let's WriteTry these writing assignnients with

students.I. According to American Indian legend..the Grand Canyon was formed when a godhit the earth with a giant ax. Another talecredits Paul Bunyan with the deed. Thestory says.Paul carelessly dragged a heavypeavey (hook for moving logs) behind himas he strolled along. The sharp hook dugthrough the ground creating the deep can-yon. Make up your own tall tale to explainhow the Grand Canyon was formed.2. Imagine yourself on John Wesley Pow-ell's first expedition through the GrandCanyon. The group was gone so long thatnewspapers reported it lost. Write a letterhome, telling your family that you've madeit safely out of the Grand Canyon and thatPowell's expedition was a'success. Thentell them about the most challenging ex-periences of your trip.

BibliographyAngier.. Bradford. How to Stay Alive in

the Woods. Collier Books, 1956.Moore, Ruth. The, Earth We Live On.

Alfred A. Knopf, 1971.Ogburn, Charlton, Jr. The Forging of Our

Continent. American Heritage Publish-ing Co., Inc., 1968.

Our Continent: A Natural History of NorthAmerica. National Geographic Society,1976.

Sandra 'Markle is INSTRUCTOR'. science con-sultant. She teaches science in the classroomand on television.

INSTRUCTOR,; May 1983