Download UNIT C ARIZONA EXCURSIONS ARIZONA ON LOCATION The

UNIT C ARIZONA EXCURSIONS
ARIZONA ON LOCATION
The White Mountains
How Mountains Affect Weather
The sun's radiation brings warmth to Earth's surface. But when warm air near the ground is
pushed up, that air gradually becomes cooler. This means that the higher you climb on a
mountain, the lower the temperature is. At night, with no heat coming from the sun, the
temperature can fall still lower. At elevations like those in the White Mountains, the
low temperatures make snow sports possible even when lowlands nearby are warm.
Mountains affect weather in another way, too. As winds blow moist air against mountains,
the air is pushed up and becomes cooler. The lower temperature causes water vapor in
the air to condense, forming clouds. That's why the tops of some mountains are covered
with clouds almost all the time. On a mountain, the side that gets more wind gets more
rain and snow. The air on the other side of the mountain is usually warmer and drier.
Skiing is one of the snow sports that people enjoy in the White Mountains.
The climate on opposite sides of a mountain range can be very different.
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Sports in the White Mountain
The White Mountains are about 350 km (220 mi) east of Phoenix and about 400 km (250
mi) north of Tucson. They're about halfway between the northern and southern borders
of the state. The White Mountains have three peaks that rise to more than 3000 km
(10,000 ft). The high elevation in the mountains makes the climate cool. But during the
summer, the snow melts and visitors can enjoy swimming and fishing in the mountain
lakes. Even in the summer, though, nighttime temperatures are low.
During the winter, people come to the White Mountains to enjoy snow sports. There are four
areas for cross-country skiing. A chairlift that carries people up a mountainside for the
view in the summer doubles as a ski lift in the winter. Other snow sports in the White
Mountains include tubing, sledding, snowshoeing, and snowboarding. Ice fishing is
popular at the frozen lakes.
Think and Do
1. SCIENCE AND TECHNOLOGY How do meteorologists predict temperatures in
different regions? Use the Internet or an encyclopedia to find out how they use
satellites, radar, and weather balloons.
2. SCIENTIFIC THINKING Which side of the Rocky Mountains do you think has more
rainfall—the east side or the west side? Be ready to give your reasons.
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ARIZONA ON LOCATION
The Salt River Project
The Hohokam people lived in Arizona long ago and farmed the land. About 2000 years ago,
they built small villages in the area where the Gila River meets the Salt River. They
planted corn, beans, squash, and cotton on small mounds near the rivers. To keep their
crops growing, they faced the difficult task of bringing river water into the very dry
countryside. These clever people solved the problem by building a network of canals.
With only stone-age tools, they dug canals that used gravity to move the needed water
onto the desert land. Eventually, the Hohokam people lived in the large region between
the present-day locations of
Flagstaff and the Mexican border. About the year 1450, however, the Hohokam civilization
died out.
Water stored in Theodore Roosevelt Lake helps Arizona meet its needs during very
dry years.
The Theodore Roosevelt Dam was the first major structure to be completed in the Salt
River Project.
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A New Use for Old Technology
Centuries later, when United States settlers first moved west to the same region, they used
the Hohokam canals to irrigate their own crops. As more people came to the region and
the need for farmland increased, the settlers had to make a change. The Salt River was
very low in some years, but it brought huge floods at other times. What the farmers
needed was a way to store water so that they could have a steady supply. By 1867, the
farmers of the area began to extend the Hohokam canals and build dams. As the city of
Phoenix became larger, the need for water continued to grow.
Modern Technology Brings Improvements
To regulate the water supply in the region, people began to build the Salt River Project, a
series of dams and canals, in 1903. The first major structure, the Theodore Roosevelt
Dam, was completed in 1911. Today, the project's six dams control the Salt River and
the Verde River. The dams, along with 250 wells, provide water to about 97,000
hectares (240,000 acres) of land in cities and the countryside. Besides providing muchneeded water, the project controls flooding. in addition, electricity produced by the
dams serves more than 700,000 customers.
Besides regulating Arizona's water supply, the Salt River Project produces electricity.
1. SCIENCE AND TECHNOLOGY Explain how the Hohokam people were able to
move water through their irrigation canals.
2. SCIENTIFIC THINKING How have Arizonans planned
for and responded to drought?
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ARIZONA ON LOCATION
The Arizona Department of Environmental Quality
In 1986, Arizona's lawmakers formed the Arizona Department of Environmental Quality
(ADEQ). ADEQ's job is to protect the state's environment and public health. It oversees
the state's air, land, and water resources. ADEQ detects and controls levels of factory
smoke, vehicle fumes, and other pollutants in the air.
A Network of Monitoring Sites
Monitoring sites throughout the state collect air samples and report their findings to ADEQ.
The sites test air samples by using certain instruments. One type of instrument moves a
clean filter back and forth in the air for a certain length of time. The amount of dust and
particle matter caught on the filter shows whether the air is clean. Other instruments
measure the
amounts of gases, such as methane, in the air. Information from ADEQ helps scientists
understand how air quality affects people's health. Officials use the information to
detect the sources of pollution in order to reduce it.
Air monitoring sites throughout Arizona provide information to the Arizona
Department of Environmental Quality.
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Arizona's Smog and Dust Storms
You know that the state of Arizona is filled with beautiful scenery. It has lush forests with
many shades of green. It has the interesting shapes and colors of the Grand Canyon.
And it has the many bright colors of wildflowers. For part of the year, however, a
brown haze hangs in the air. That haze, called smog, prevents people from clearly
seeing the colors of the Arizona landscape. It also causes respiratory problems like
asthma. Smog forms when sunlight reacts with tiny particles of air pollution on days
that are not windy.
Arizona has another unusual air-quality problem: dust storms. You know that a heat source
can cause convection currents. This means that the air above the heat source becomes
warmer and lighter, so the air is pushed up. Cold air moves in to replace it. Then that air
warms and moves up, too. Very hot desert sand can create convection currents, forming
winds. As the winds gain strength, they pick up clouds of sand or dust and become dust
storms. Large dust storms are rare in the United States, but they can be very powerful.
They can be so strong that people can't even see the sun.
A dust storm is a strong, dry wind that carries clouds of blowing sand or dust.
Visibility in downtown Phoenix is decreased when smog forms.
1. SCIENCE AND TECHNOLOGY Do you think that scientists can use technology to
prevent dust storms? Explain.
2. SCIENTIFIC THINKING What do you think is the biggest air-quality problem in
Arizona? Write a letter to your school newspaper, describing the problem, and suggest a
way to solve the problem.
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ARIZONA PROJECTS AND INVESTIGATIONS
Discover a New Organism
Materials
 Drawing supplies
 Unlined paper
Procedure
1. Consider these facts about Arizona.
 About 350 million years ago, the land that is now Arizona was covered by a huge sea.
 The sea contained a great many types of living things.
2. Think about how living creatures in the ancient sea were able to survive. What foods do
you think they ate? How did the sea creatures move in the water? How did smaller creatures
protect themselves from predators? Were the sea creatures able to see and hear, and could
they sense warmth or cold?
3. Imagine that you've just discovered the fossil of a creature from the ancient sea. Draw the
creature, and label each part that would have been used for obtaining food, for moving
about, or for protection.
4. Give your invented creature a name. Be ready to tell the class about the creature.
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Create a Weather System Model
Materials
 Internet access or today's newspaper
 Outdoor thermometer and other instruments to measure weather
 Outline map of Arizona
Procedure
1. On the outline map, label the place where you live. If there are desert areas, lakes, or
mountains nearby, show them on the map.
2. On the Internet or in the newspaper, find a map that predicts today's weather for your
region. On your outline map, record the predicted high temperature. Draw symbols on
your map to show predicted conditions such as sun, clouds, rain, fog, or snow. Include
markings for the predicted atmospheric pressure.
3. Throughout the day, observe the weather to see whether the predictions have been
accurate. Check the thermometer to see how high the temperature gets. On your outline
map, add notes about the accuracy of the predictions. Do this for as many of the
predictions as you can.
Draw Conclusions
1. Why do you think the weather predictions were accurate or not accurate?
2. If you live near mountains or lakes, how do you think they affected today's weather?
How do you think atmospheric pressure affected the weather?
Extend the Activity
Make a weather map for the entire state on several days. What trends do you notice? Are
there areas whose temperatures are usually higher or lower than those where you live?
Are there areas that usually have more clouds or rain?
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