Sra: Imagine It!, Themes, Taking a Stand, Ancient Civilizations Ecology, Great Expectations, Earth in Action, Art and Impact, Level 6

Write about It!

Write an inscription for a monument honoring the volunteers of the 1993 flood. Try to describe their dedication and charity in forty to fifty words.

Remember to look for pictures of items formed by Earth in action for the Concept/Question Board.

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Science Inquiry: Energy from Water

Genre

Feature

Water thunders over cliffs; it rushes down rivers. The movement of water contains plenty of energy. For centuries, people have used the kinetic energy, or energy of motion, in moving water. They used this energy to turn waterwheels. The waterwheels then used mechanical energy to power small mills, grindstones, saws, and other tools. The first large factories used machines powered by moving water.

Modern power plants use waterpower to make electricity too. Sometimes the builders of a power plant need to dam a stream or river. By holding water in a reservoir, the dam raises the water level. The water level behind the dam is much higher than the level of the power plant at the bottom. Whenever electricity is needed, the water is released to rush down with terrific force. The kinetic energy in the falling water turns the blades of a turbine. These turbines power generators, which make electricity.

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Production note: this image crosses the gutter to appear both on page 572 and page 573 in the print version.

It is best to keep a waterpower plant operating twenty-four hours a day. However, demand for power is not always the same. The average person or business uses electricity at the same times of day. During off hours, such as late at night, not as much electricity is used.

Waterpower companies try to store the energy that is generated during off hours. At some plants, extra electricity is used to pump water back up to the reservoir. Then the same water can be used again when electricity is needed.

This water not only can be reused; it is renewable. It is constantly being replaced by the water cycle. It falls as rain and then travels to waterways.

Besides being a renewable resource, waterpower does not pollute the air. For these reasons, some people feel we should rely more on waterpower for our energy needs.

Think Link

How does the sequence diagram help you understand how water is used to make electricity?

What are the disadvantages to using dams and waterpower that the author does not mention?

What would you like to learn more about this topic? Where could you find information?

Try It!

As you work on your investigation, think about how you can use sequence diagrams to organize your information.

Vocabulary Strategy

Sometimes you can use word structure to determine the meaning of a new word. For example, the word revived is a combination of the prefix re- , which means "again"; the Latin word vivere , which means "to live"; and the suffix - d , which signals use of the past tense.

Living in Oklahoma, I am accustomed to rain showers during the spring. In fact, I count on storms to keep my gardens watered. It seems that I hardly ever pull out the water hose because there are so many storms where I live.

Unfortunately, after the last storm, I let too much time elapse before I watered the plants. I did not expect the clear, dry weather to persist for so long. Monday morning I found some of the plants wilting in the sun and heat. Luckily, all the plants seemed to still be alive.

I was so worried about my plants that I did not check the sky for any signs of rain. I revived my plants with a good soaking from the hose. While the ground was wet and soft, I also wrenched some weeds from between the rows of tomatoes and peppers. The recent weather reminds me of what it must be like to live in the desert. I have a friend who lives in the West, where it hardly ever rains.

Early Monday afternoon I noticed the phenomena that signal a coming storm. A column of dark clouds quickly built in the sky. Sure enough, a few drops of rain fell. The crows that dwell in the nearby fields flew nearer to the ground. I was reminded of the old saying "When crows fly low, the winds are going to blow."

From the looks of the clouds, I predicted thunder and lightning as well, but nothing more severe. An occasional tornado will tear through our region. However, a thundercloud will not cause tornadoes unless the air within it spirals at high speed. If it does, a whirling funnel of air might descend from the cloud and rip across the countryside.

We did have thunderstorms that day. They were fierce but not too scary. And my plants received plenty of water!

Concept Vocabulary

The concept word for this lesson is dynamic. Dynamic means "strong, energetic, intense, or forceful." How does dynamic connect with the theme Earth in Action?

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Genre

* Expository Text tells people something. It contains facts about real people, things, or events.

Comprehension Skill: Author's Purpose

As you read, identify the reason, or purpose, the author has for writing the text. This skill will give you an idea of what to expect from the selection.

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by Carole G. Vogel

Focus Questions

How are this Lakota Sioux myth and the expository text that follows connected?

How has science caused a movement away from explaining the weather with myths and folklore?

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The warriors of thunder and lightning dwell in stormy skies. Mounted on giant white horses, they wildly ride the billowing black clouds. Their fists clasp lightning sticks, which light up the sky. The hoofs of their galloping horses create the crashes of thunder heard below.

Since the early days the people of the plains had become accustomed to the occasional clatter above. They knew that sometimes a lightning stick would slip from a warrior's hand and strike a tree or even a tepee. However, most of the time when black clouds churned overhead, the mounted warriors of thunder and lightning dashed madly about without harming anyone or anything beneath them. The people were grateful for the storms because they brought rains that revived the plants and refreshed the streams.

But one summer morning a hunting party left their camp near the Black Hills of South Dakota in search of buffalo. Throughout the day the sun beat down, turning the air hot and heavy. Thick dark clouds rolled in from the west, coloring the sky a deep purple. On the ground, wind gusts stirred up the dust.

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The men came upon a buffalo herd but decided to wait out the advancing storm before beginning the hunt. An immense thundercloud soon filled the horizon, and lightning flickered across the sky. Accustomed to storms, the men sensed unusual danger in this one. Their apprehension grew deeper when they noticed part of the cloud dipping menacingly close to the ground.

Inside the billowing mass, the thunder and lightning warriors raced crazily back and forth on their steeds. Deafening booms from the trampling hoofs shook the air and rattled the ground. Lightning sticks created blinding flashes of light shaped like tree roots, capable of striking many objects at one time.

Uneasy, the buffalo crowded together in a tight group. Glowing blue sparks of light appeared on the tips of their horns. Suddenly the skies blackened, the wind shrieked, and great drops of rain pounded down. The frightened animals snorted and pawed the ground.

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Before the buffalo could stampede, the cloud swooped down upon them. The warriors astride their giant horses charged the herd. The panicked buffalo tried to flee, but the warriors were too fast. As the hunters on the ground watched in terror, the sky warriors began to strike the animals dead with their powerful lightning sticks. The wind swirled and roared, forming a gigantic cone that hurtled the buffalo up into the air.

Lightning will strike our planet nearly 9 million times within the next 24 hours. That breaks down to roughly 100 zaps of lightning per second. In the United States, Florida has the distinction of being the state with the most lightning.

Lightning usually forms in towering thunderclouds 15,000 to 20,000 feet above the ground. Even though thunderclouds are enormous, the cause of lightning is extraordinarily small.

Like all matter, the water droplets and ice crystals in a thundercloud are made of atoms. You probably know that each atom consists of protons, neutrons, and electrons. A proton has a positive charge, and a neutron has no charge. Together, they make up the nucleus, or center, of the atom. The nucleus has a positive charge. Electrons whirl around the nucleus. They have a negative charge.

Usually, the number of electrons in an atom equals the number of protons. Thus the positive charges and the negative charges are balanced and the atom has no charge. However, collisions with other atoms can upset the balance. Electrons can be lost or gained.

You can upset the balance of electrons in your hair by rubbing your head with a balloon. Your hair, which started with an equal number of electrons and protons, loses electrons to the balloon. Your hair now has more protons than electrons. It carries a positive charge. The balloon has more electrons, so it carries a negative charge.

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If the day is dry and you rub the balloon on your head in a dark room, you may see little flashes of light in a mirror and hear crackling sounds. The electrons that piled up on the balloon jumped back onto your hair, creating a tiny spark of electricity.

Something similar happens in a thundercloud, only on a much grander scale. Strong updrafts hurl ice crystals and water droplets up and down within the clouds. Some of the ice crystals and water droplets get pulled apart, and they develop electrical charges. The top of the cloud becomes positively charged, while the bottom of the cloud develops a negative charge.

Eventually the charges build up so much that the negative ones jump toward the positive, creating a streak of lightning. The gigantic spark may leap from one part of a cloud to another or from cloud to cloud. If enough electrical attraction exists between the cloud and positive charges on the ground, lightning darts to the Earth's surface.

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Perhaps the eeriest display of electrical phenomena is Saint Elmo's fire, the strange blue glow that appeared on the horn tips of the buffalo in the preceding legend. Saint Elmo's fire is a lightning bolt that fizzled. It occurs when the damp air next to the tip of an object develops a positive charge. Electrons from the surrounding air leap toward the positive charge, causing a steady blue glow in the air. The attraction between the opposite charges is not great enough to generate a lightning flash. Saint Elmo's fire has been spotted on church steeples, ship masts, and airplane wings, as well as on the horns of cattle and buffalo. It is harmless. Ordinary lightning, however, is usually deadly.

Under the right conditions severe thunderstorms can give birth to tornadoes. Tornadoes are swirling funnels of air that can drop down from thunderheads. They arise in the violent clashes of air masses with different pressures: usually a cold, heavy air mass from the poles slams into a light, warm air mass from the tropics.

At the storm front, powerful winds develop as warm air soars upward while cool air swooshes down to take its place. A thin line of thunderstorms begins to brew. Deafening thunderclaps reverberate through the air. Lightning slashes the sky. Rain and hail rocket downward.

At the storm's peak, the inrushing air spirals at tremendous speed around a center of low pressure. A funnel appears at the base of the cloud. Like a giant straw, it can slurp up nearly everything beneath it, even a herd of buffalo. Whirling soil and debris trapped in the tornado give the funnel its black coloring.

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The life span of the average tornado is only a few minutes. It measures 150 feet across, careens across the land at a speed of 30 miles per hour, and cuts a swath of destruction about 2 miles long. However, it is the long-lived, but fortunately rare, monster tornadoes that make the headlines. Traveling at 60 miles per hour, they may persist up to three hours or so with wind speeds exceeding 300 miles per hour. They may cut a path more than a mile wide and more than 60 miles long.

Carole G. Vogel

Vogel has always loved powerful weather. She remembers watching a fierce thunderstorm as a child with her father, who is a scientist. He told her about the science behind the booming thunder and flashing lightning. Now that she is an author, Vogel celebrates nature in her writing. Her books teach about nature and show how thrilling it can be. She wants people to understand that natural disasters actually keep Earth healthy.

Meet the Illustrator

Ron Himler

On a trip to the American Southwest in 1972, Himler attended Native American ceremonial dances and found inspiration for capturing these impressions as illustrations within children's books. "The powerful psychological effect of the dances opened a door to a people and a time to which I felt an inexplicable empathy," Himler has said. He received the Silver Medal at the Society of Illustrators exhibition in New York for "Best Western Painting in Book Cover Art" in 1992 and was also a finalist in the Western Writers of America Best Western Book Cover Art.

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Production note: this image crosses the gutter to appear both on page 586 and page 587 in the print version.

Earth in Action: Theme Connections

Within the Selection

Across Selections

Beyond the Selection

Write about It!

Write a list of the warning signs that precede a fierce storm.

Remember to look for pictures of tornadoes and lightning for the Concept/Question Board.

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Science Inquiry: Technology and Storm Trackers

Genre

Feature

Scientists who study the weather, or meteorologists, did not always have the ability to know when storms would come. In fact meteorologists were often at risk when they first tried to observe storms. Today scientists have more powerful tools with which to work. These tools allow them to stay out of harm's way.

For example, Doppler radar allows scientists to observe storms many hours before they arrive. Wind speed and direction of storms can be determined when radio waves are reflected from the storm.

Strong thunderstorms are monitored closely. Meteorologists use images gathered from satellites and radar. This data allows them quickly to spot areas of rotating air within a thunderstorm in case a funnel starts to descend from the clouds.

Weather science has changed over time. During the 1970s, the National Severe Storms Laboratory worked with the University of Oklahoma to build mobile storm research programs. Daring storm chasers actually sought tornadoes, driving out into their predicted paths. A device called TOTO (Totable Tornado Observatory) would be dropped into a tornado's path in the hope that it would be swallowed by the tornado. TOTO could then gather data related to pressure, humidity, temperature, and wind speed.

In the 1980s and 1990s, smaller and lighter versions of TOTO (called Turtles) were used. Unfortunately, neither TOTO nor Turtles successfully came in direct contact with a tornado.

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Scientists also use the Fujita scale, which classifies the size and strength of tornadoes. The scale begins with an "F0," which means that the tornado has caused light damage. It goes up to "F6," although a tornado this violent has never been recorded. The size and damage caused by an F6 tornado is hard to imagine.

Modern weather science helps save lives. As this science develops, it will allow scientists and city officials to send out earlier warnings to citizens before bad weather arrives.

How does the chart help you understand how scientists rank tornadoes?

What are some important reasons that technology is needed to measure phenomena in tornadoes from a distance?

Think about a tornado in the news. Were scientists able to predict it? Did they warn people in time? How did people respond to the warning?

Try It!

As you work on your investigation, think about how you can use charts to organize your information.

by Robert Winner

It will finger at the edges of the cliffs.

It will poke into the edges of the land.

It will cover and conceal its own turmoil.

It will come up over the edges

and again there will be green slime among the cliffs

and shells singing along the beaches

and a murmur among the grasses at the edges of the land

and water stirring among the grasses.

Long after the skulls of cities have decayed

the sea will drift among the grasses.

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by Marilyn Singer

Volcanoes there are that sleep

the sleep of dragons

With cool heads and hot bellies

they crouch

solid and still

where the earth meets the sky

Till something wakes them

Then furious they breathe fire and smoke

hot spittle and wrath

to burn and choke

whatever lies in their path

leaving in their wake

an odd treasure

of stone sponges and glass

and an occasional lake

Test-Taking Strategy: Referring to a Story or Article to Answer Questions

To answer some questions on a test, you may have to read a story or article. You must use the information in the story or article to answer the questions.

Referring to a Story or Article to Answer Questions

Sometimes you will read a story or article on a test and answer questions about it. It is very important that you use the information in the story or article to answer the questions. You do not have to memorize the story or article. You need to read it and try to understand what you read. You should look back at the text to answer the questions.

Read the story and the question below. Use the story to decide which answer is correct.

It was a cool morning. The swimmers were wearing warm clothes. They were stretching or jogging in place. Practice would start in a few minutes, and they all wanted to be ready. The big meet was only a few days away.

The swimmers in this story want to be ready for practice because--

A the pool would get crowded

B it was a cool morning

C a big meet was coming up

D the coach was strict

Look at the story. Compare each answer to the story. Which answer is mentioned in the story and goes with the question? The story mentions that a big meet is just a few days away. That is why the swimmers want to be ready. The story says nothing about crowds or a strict coach. The morning was cool, but this did not make the swimmers any more ready. The third answer is correct.

You should always use the information in a story or article to answer questions. Do not try to memorize the text. You can look back at it to answer each question.

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