Natural Disasters LESSON 4 · 2018. 9. 10. · United States, Alaska and California have the most earth-quakes (Figure 24). People who live in these high-risk areas can take precautions

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LESS

ON 4

ON JANUARY 12, 2010, an earthquake with a magnitude of 7.0 shook the nation of Haiti. Homes and buildings collapsed and thousands of people were either killed or injured. Huge plumes of dust covered the capital city of Port-au-Prince, exposing the residents to polluted air.

Earthquakes are just one example of how the forces of Earth, wind, and water can quickly and completely disrupt our lives. Other examples of physical hazards that occur naturally in the environment and pose health hazards include volcanic eruptions and violent storms, includ-ing hurricanes and tornadoes. We can do little to predict the timing of a natural disaster such as an earthquake, and nothing to prevent one. However, scientists can map geologic faults to determine areas at risk of earthquakes, engineers can design buildings in ways that help them resist damage, and citizens and governments can take steps to prepare for the aftermath of a severe quake.

Some common practices increase our vulnerability to certain physi-cal hazards. Deforesting slopes makes landslides more likely, for instance, and damming rivers makes flooding more likely in some areas while preventing flooding in others. We can reduce risk from such hazards by improving our forestry and flood control practices and by choosing not to build in areas prone to floods, landslides, fires, and coastal waves.

Earthquakes The shaking that occurs during an earthquake can destroy

natural landforms as well as human-made structures.

The forces that move mountains are also the ones that create earthquakes. Earth’s crust is broken into several large sections called tectonic plates. These hard plates “float” on a layer of hot, soft rock. As plates scrape against each other, sometimes they get stuck and the stress builds up. When the plates finally move, energy is released. This energy causes the earth to shake, a phenomenon called an earthquake.

Natural Disasters

• Discuss how earthquakes affect structures on Earth’s surface.

• Discuss how volcanoes affect human lives and property.

• Describe tornadoes, hurricanes, and thunderstorms.• Discuss the dangers of avalanches.

Reading Strategy Create a three-column table. Label the first column Hazard, the second column Damages, and the third column Safety and Preparation. As you read the lesson, fill in the first column with each physical hazard discussed. Take notes on the damage each causes and how to prepare for and stay safe during each.

Vocabulary earthquake, landslide, tsunami, volcano, tornado, hurricane, thunderstorm, avalanche

Guiding Question: How can physical events in the environment affect our health?

9.4 Lesson PLan PreviewDifferentiated Instruction Advanced students research and present information about earthquake-safe structures.Real World Investigate and discuss the types of warning systems that are in place for severe storms in their area.Inquiry Students research and present information on the factors that contribute to avalanches.

9.4 resources Map It Online • Lesson 9.4 Work-sheets • Lesson 9.4 Assessment • Chapter 9 Overview Presentation

FOCUS Ask volunteers to share any personal experiences they may have had with a natural disaster, such as an earthquake, tornado, or hurricane. For example, have they experienced one or know someone who has? Ask them to talk about the effects the disaster had on them and others.

GUIDING QUESTION

Map it

0133724751_a210Earthquake zones/plates26p x 14p7

FINAL

12.04.09

Major earthquakePlate boundary

KEY

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Figure 23 Earthquake Damage in Haiti

Figure 24 Earthquakes and Tectonic Plates

Surface effects Depending on where they occur, how much energy is released, and how long the earth shakes, earthquakes can have extensive effects on Earth’s surface. For example, earthquakes can cause the ground to sink and soil to liquefy. They can also set off landslides, which occur when rock and soil slide down a slope. When an earthquake triggers a landslide, it can be a very dangerous event for people nearby. In 1970, an earthquake in Peru set off a landslide that killed about 18,000 people.

When an earthquake occurs at the bottom of the ocean, it can set off a tsunami. A tsunami is a large ocean wave. When tsunamis hit coastal towns, they can cause massive damage and loss of life. In December 2004, an earthquake at the bot-tom of the Indian Ocean generated tsunami waves that killed more than 200,000 people in Southeast Asia, Sri Lanka, India, Thailand, and other coastal areas.

earthquake Damage Earthquakes can be incredibly costly events, both in terms of structural damage and human life. For example, in Haiti, the death toll is estimated to be more than 150,000.

earthquake Safety Scientists cannot predict when earthquakes might occur. There are places, however, where earthquakes are more likely to occur than others. In the United States, Alaska and California have the most earth-quakes (Figure 24). People who live in these high-risk areas can take precautions to help them survive an earthquake if it does occur.

If you are caught in an earthquake, try to take cover under something sturdy. Cover your face and head. Keep clear of anything that may fall or break on you, such as hanging lights and windows. Stay away from buildings, power lines, and streetlights. Predicting Earthquakes

Figure 24 shows where the major earthquakes occurred between 1980 and 1990. The red dots indicate loca-tions of the earthquakes. The orange lines are the boundaries of the tecton-ic plates. Study the map and answer the following questions.

1. Observe What general pattern do you observe between the location of earthquakes and the location of the tectonic plates?

2. Interpret Maps Do most earth-quakes take place in the interiors of the continents or along the coastlines?

ANSWERS

Map it1. Students should notice that the majority of

earthquakes occur where the plates meet.2. Along the coastlines

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Volcanoes The molten rock, gas, ash, and cinders released during a volca-

nic eruption can cause significant damage and loss of life in nearby cities and towns.

A volcano is an opening in Earth’s crust through which lava, ash, and gases are ejected. When molten rock inside Earth comes to the surface, it is called a volcanic eruption. In an eruption, rock may seep quietly out of the land or it may explode. Eventually, the rock hardens and forms a new rock layer on Earth’s surface.

Damage From Volcanic Eruptions The molten rock, or lava, that surfaces in a volcanic eruption can cover large areas of land, destroying what was once there. Volcanoes can also spew clouds of gas, ash, and cin-ders into the atmosphere. In 2010, a volcanic eruption in Iceland sent so much ash into the atmosphere that air traffic between Europe an the rest of the world was severely disrupted for about 10 days (Figure 25). Clouds from extreme volcanic eruptions can block the sun’s rays and cause global temperatures to drop. Eruptions can also trigger landslides and mudflows. Mudflows are large masses of soil, rock, and water sliding down a slope.

The 1991 eruption of Mount Pinatubo in the Philippines is a powerful example of the destructive potential of volcanoes. The valleys surround-ing the mountain filled with thick deposits of volcanic material. Deposits in some areas were over 180 meters (600 feet) thick! The eruption set off mudflows and sent up a massive ash cloud about 35 kilometers (22 miles) into the air. Some of the ash settled onto nearby roofs and mixed with rain. This heavy mix caused roof collapses that killed most of the 300 people who died from the eruption.

Preparing for a Volcanic Eruption Like earthquakes, many volcanoes are located near the edges of tectonic plates. Scientists moni-tor volcanoes to try to predict when they will erupt. They cannot tell for certain the size of an eruption or predict far in the future when one might occur. However, scientists can sometimes warn people in time to evacu-ate. Before Mount Pinatubo erupted, scientists warned people far enough in advance that more than 70,000 people were evacuated.

FigurE 25 Eyjafjallajokull and Mount Pinatubo (a) The ash trail from Eyhafiallajokull volcano in Iceland extended from Iceland to western Europe disrupting air traffic for days. (b) Ash from the eruption of Mount Pinatubo in the Philippines remained in the air for days, (c) coating villagers as they left the affected area.

(c)

(b)

(a)

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Figure 26 Tornadoes A tornado often destroys anything in its path.

Storms Tornadoes, hurricanes, and thunderstorms are powerful

weather events that can damage property and threaten human lives.

Geologic forces are not the only physical hazards powerful enough to devastate towns and cities. Storms, such as tornadoes and hurricanes, can also claim lives and homes.

Tornadoes A tornado is a type of windstorm in which a funnel of rotating air drops down from a storm cloud and touches Earth’s surface. Funnel wind speeds can reach over 400 kilometers (250 miles) per hour.

▶ Tornado Damage Tornadoes can cause incredible damage where they touch down. Tornadoes can flatten houses, lift cars, and tear the bark off trees. They can also be deadly. In 2009, twenty-one Americans were killed by tornadoes. The majority of people who die in a tornado are struck by flying objects that have been picked up by the strong winds.

▶ Tornado Safety If you are indoors, seek shelter in the lowest floor of the building, such as the basement. If you are in a vehicle or mobile home, get out and find the nearest sturdy building for shelter. If you are stuck outside, try to find a ditch or a low point and lie face down in it. Try to protect your head as best as possible.

Hurricanes A hurricane is a powerful storm that forms over the ocean in the tropics. Hurricanes produce winds that are at least 119 kilometers (74 miles) per hour. When a hurricane strikes land, it brings high winds, heavy rain, and a storm surge along with it. A storm surge is a dome of water that crashes along the coast where the hurricane hits.

ReadingCheckpoint

What is the difference between a tsunami and a storm surge?

What is the relationship between environmental health and our own health?Perspective Have students consider how an individual’s perspective of the impact of natural disasters on human health is influenced by where they live. Point out that earthquakes, volcanic eruptions, tor-nadoes, hurricanes, thunderstorms, and avalanches occur with differing frequency in different areas. Have students choose different areas of the country. Ask them to research and share information with the class about the types of natural disasters most likely to affect human health in the area they have chosen.

BIG QUESTION

ANSWERS

Reading Checkpoint A tsunami is a large ocean wave often caused by an earthquake. A storm surge is a dome of water that crashes along the coast where a hurricane hits.

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▶ Hurricane Damage Hurricanes can destroy buildings, wash away beaches, and blow away trees. They can also cause severe flooding. Hurricane Katrina is one clear example of the destructive power of hurri-canes. In 2005, Hurricane Katrina struck land for a second time about 72 kilometers (45 miles) southeast of New Orleans, Louisiana. It had winds that were about 201 kilometers (140 miles) per hour and a storm surge over 8 meters (26 feet) high. Its powerful forces caused the levee system in New Orleans to break. Levees are structures built alongside waterways to prevent flooding. When the levees broke, water rushed into New Orleans, eventually submerging about three quarters of the city. Katrina killed 1800 people and caused more than $80 billion in damage.

▶ Hurricane Safety To prepare for a hurricane, secure your home before it hits. For example, close storm shutters and clear rain gutters. If local authorities tell you to evacuate, do so. During the hurricane, try to stay away from windows. If necessary, take shelter in an interior room under a sturdy object.

Figure 27 Hurricane Katrina On August 25, 2005, Hurricane Katrina hit the southern coast of the United States with devastating effect. Katrina caused widespread devastation along the central Gulf Coast states of the United States. Cities such as New Orleans, Louisiana (a and b), Mobile, Alabama, and Gulfport, Mississippi (c), bore the brunt of Katrina’s force.

(b) (c)

(a)

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Lightning Bolts

Thunderstorms A thunderstorm is a storm that produces both lightning and thunder. Thunderstorms also usually produce heavy rain and sometimes hail. Thunderstorms are common events. At this very moment, there are probably about 2000 thun-derstorms in progress around the globe. But just because they are common does not mean that thunderstorms are harmless.

▶ Thunderstorm Damage Heavy rain from thunderstorms can cause flooding. Strong winds can take down power lines and trees. If a severe thunderstorm generates large hail, it can damage crops and property. And, lightning can start fires and kill people when it strikes. In 2007, forty-five Americans were struck and killed by lightning.

▶ Thunderstorm Safety The best way to stay safe in a thun-derstorm is to stay indoors. If you are outside, stay away from tall objects such as trees and poles. Squat down and keep your head low.

Avalanches An avalanche is a mass of sliding snow that can bury

people and places in its path.

An avalanche is a mass of snow sliding down a slope. In North America, a big avalanche might send 300,000 cubic yards of snow crashing down a mountain. This is roughly equal to 20 football fields, each filled with snow that is about 3 meters (10 feet) deep.

Avalanche Conditions There are certain conditions that create the potential for avalanches. Avalanches usually occur on slopes that are greater than 30 degrees. Another factor is the snow-pack, or the layers of snow on the slope. Unstable snowpacks cre-ate the potential for an avalanche. A snowpack is unstable when a layer of hard, strong snow sits on top of soft, weak snow. If the weak layer gives, the snowpack can break apart and send a mass of snow sliding down the slope.

Weather is another significant factor for avalanches. Heavy snowfall adds weight to the snow pack and can trigger an ava-lanche. Warm temperatures can also influence snowpack stability. Initially, warm temperatures can melt the top of the snowpack and increase the potential for an avalanche. However, if periods of melting and re-freezing occur, the snowpack can actually become more stable.

Avalanche Damage Avalanches can bury both people and places in large masses of snow. In 2008 and 2009, twenty-seven Americans died in avalanches. Avalanches can block roads and railroad tracks as well as damage phone lines and bridges.

ANSWERS

Lesson 4 Assessment

1. When rock and soil slide down a slope

2. Sample answer: Lava, ash, and cinders can bury homes and build-ings causing the roofs or even entire buildings to collapse. Landslides and mudflows can bury or damage struc-tures that may be in their path.

3. Both hurricanes and tornadoes are powerful storms that produce strong winds. A tornado is a funnel of rotat-ing air that drops down from a storm cloud and touches Earth’s surface. A hurricane, on the other hand, is a storm that forms over the ocean. When it reaches land it brings heavy rains and a large storm surge.

4. Staying calm will help you conserve any air you have.

5. Sample answer: I would look for the nearest sturdy building. Then, I would leave my car, go inside the building, and find the lowest level to take shelter in.

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1. Review What is a landslide? 2. Explain Name some ways a volcanic eruption can

damage property. 3. Compare and Contrast How are hurricanes and

tornadoes similar? How are they different? 4. Apply Concepts Why do you think it is important

to stay calm if you are caught in an avalanche?

5. Suppose you are in a car driving through a new town. The national weather service issues a tornado warning for this area. At the same time, you notice the weather looks threat-ening. What might you do?

4

Figure 28 Avalanche Damage This road and bridge have been completely destroyed by an avalanche.

Avalanche Safety Most Americans who die in avalanches are on the slopes for recreation, skiing, snowboarding, or hiking. The best way to stay safe while participating in one of these activities is to avoid risky slopes altogether. If you do get caught and buried by an avalanche, try to stay near the surface. Swim up through the sliding snow as best you can. Stay calm and try to conserve any air you have.

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