Ebooksclub.org Tsunamis Earth 039 s Power

8/9/2019 Ebooksclub.org Tsunamis Earth 039 s Power

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An Active Planet . . . . . . . . . . . . . . . . . . . . . . . . . .4 At Risk . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .7Tsunami or Tidal Wave? . . . . . . . . . . . . . . . . . . . .8Dangerous Waves . . . . . . . . . . . . . . . . . . . . . . . .11Earthquakes and Tsunamis . . . . . . . . . . . . . . . . .15The 2004 Indian Ocean Tsunami . . . . . . . . . . . .16Volcanoes and Tsunamis . . . . . . . . . . . . . . . . . . .19Krakatau . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .201958 Alaska Tsunami . . . . . . . . . . . . . . . . . . . . . .23

Tsunami Warning! . . . . . . . . . . . . . . . . . . . . . . . .24Taming the Wave . . . . . . . . . . . . . . . . . . . . . . . . .28Glossary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .30Further reading . . . . . . . . . . . . . . . . . . . . . . . . . .31

Websites to Visit . . . . . . . . . . . . . . . . . . . . . . . . .31Index . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .32

TABLE OF CONTENTS


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Earth is a busy planet. The earth and sunprovide all of the ingredients for life to thrive.But the earth is not always a gentle and forgivinghome. Natural forces on earth make it an

unpredictable place to live.Weather is a natural force that affects plants

and animals. Weather cannot be controlled, but itcan be forecasted. Even deadly weather events

such as hurricanes, tornadoes, and floods canoften be predicted. Advance warning givespeople a chance to prepare or escape. However,some forces of nature are much harder to predictand that makes them especially dangerous.

AN ACTIVE PLANET


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A s ur f e r e n j o y s b i g w a v e

s a l o n g t h e Ca l i f o r ni a c o a s t .


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Co a s t a l l i v i n g h a s n e v e r b e e n mo r e p o p u l a r .

Tsunami evacuation route signspoint the way to safety.


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AT RISK

The population in coastal communitiesaround the world increases every year. In theUnited States, more than half of all Americansnow live on or near the coast. Coastalcommunities have much to offer, but manyresidents do not realize they may be puttingthemselves at risk. What kind of risk? One of the most powerful and dangerous forces of nature, tsunamis! A tsunami is a wave, or seriesof waves caused by a sudden displacement of

water in the sea. The greater the displacement

of water, the larger the tsunami will be.

The term tsunamiis a Japaneseword meaning

harbor wave.


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Ro u g h s u r f c a u s e d by w i n d .


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T h e 2 0 0 4 I n d i a n Oc e a n t s u n a mi l e

v e l e d

l o w- l y i n g c o a s t a l a r e a s o f Su ma t r a .

s e n d s b a n d s o f r i p p l e s

o v e r t h e w a t e r .

A s t o n e t h r o w n in t o a l a k e


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DANGEROUS

WAVES

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When a tsunami is triggered, its wavesrapidly move away from their source. Similar

to the way ripples, or waves, move away from arock thrown into a pool of water. However,tsunami waves can travel hundreds orthousands of miles.

The image mostpeople have of atsunami is of a

towering wall ofwater crashing onshore. Inreality, mosttsunamis moreclosely resemblean incoming tide

that rises higherand higher.Depending uponthe coastline, atsunami may rushinland a few feetor up to a mile

or more.


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Strangely enough, most tsunamis are hard todetect until they approach shallow waters near a

coast. In the open sea where the water is deep, atsunami may not be much higher than an ordinary

wave. But it can travel at terrific speeds, 500 miles anhour or more. As it moves into shallow coastal

waters, a tsunami’s forward speed slows, but its heightincreases. Finally, the wave reaches land unleashingits full power on the shoreline.

b e a c h a n d f l o o d s t h e t o w n

Receding water issometimes thefirst sign of anapproachingtsunami. Coastalwater drawn

toward anincoming tsunamican expose areasalong the beachthat are normallyunderwater.Unsuspectingbeach goers maybe lured out toinvestigate, onlyto be caught upin the tsunamithat is sure tofollow.

Wa t e r f r o m a t s u n a mi c o v e r s t

h e

o f K a l u t a r a , Sr i Lan k a .

©Di gi t al

Gl o b e


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A s a t e l l i t e i ma g e of K a l u t a r a , Sr i La n k

a s h o w s w a t e r

receding after the first in a series of tsunami waves.©DigitalGlobe


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A t s u n a mi w a r n i n g p o s t e r d i s tr i b u t e d b y

the Philippine government.


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Undersea earthquakes are the mostcommon cause of tsunamis. Shifting rock

inside the earth causes earthquakes. If anearthquake is strong enough, it can change theshape of the surface. Powerful underseaearthquakes can alter the shape of the seafloor

in just seconds. This sudden movement of theseafloor displaces an enormous amount of

water. The displaced water creates a tsunami.

EARTHQUAKES

AND TSUNAMIS 1964-Prince

William Sound, Alaska:

Alaskanresidents whosurvived thestrongestearthquake everrecorded in the

United Statesmust have beenrelieved. Manyhad let theirguard down bythe time thetsunamis rolled

into the coast.Caused by theearthquake, thetsunami tookmany lives. Thepowerful waveskilled more than100 Alaskans.


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On December 26, 2004, a monstrous tsunami

swallowed up entire villages along the shores of the Indian Ocean. A massive underseaearthquake off the Indonesian island of Sumatra triggered the tsunami. Scientists that

study earthquakes, called seismologists ,reported that the earthquake lasted severalminutes. Most earthquakes last only seconds.One of the deadliest disasters in modern times,the Indian Ocean tsunami caused major

damage in Indonesia, Sri L anka, India,Thailand, and other countries. It is believedthat around 230,000 people died.

If there was a bright side to the disaster, it

was in the way the world community responded.Dozens of nations sent money, relief supplies,and armies of rescue workers to aid the victims.

THE 2004 INDIAN OCEAN TSUNAMI


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Survivors flock toward a helicoptercarrying relief supplies.

A p h o t o g r a p h e r s h o t t h i s i ma ge a s t h e f i r s t o f s e v e r a l

He e s c a p e d j u s t b e f o r e a l a r g e r w a v e d e s t r o y e d t h e b u i l d i n g.

waves struck Thailand during the 2004 Indian Ocean tsunami.


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Some volcanic eruptions create tsunamis. A

volcano is a vent or crack in the earth’s surface where hot magma and gas escape from deepinside the earth. Volcanoes may be quiet forhundreds of years and then suddenly erupt

with colossal force. The explosive power of aneruption beneath the sea can cause tsunamis.Landslides triggered by a volcanic eruptioncan cause tsunamis, too.

VOLCANOES

AND TSUNAMIS


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One of the largest explosions in recordedhistory took place during a volcanic eruption

on the small Island of Krakatau, Indonesia in1883. The blast was many times more powerfulthan the largest nuclear bomb ever detonated.The sound of the explosion was heard morethan 2,000 miles away. Scientists believe theeruption caused the volcano and much of theisland to collapse into the sea.

Tsunamis caused by the collapsing volcanoraced across the ocean. One of the tsunami

waves rose to at least 140 feet, swampingnearby islands. One hundred and sixty five

villages were swept away. More than 36,000people were killed.

KRAKATAU


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A s a t e l l i t e v i e w o f A n a k K r a k a t a u , o r “ c

h i l d o f K r a k a t a u . ”

Anak Krakatau grew from the remains of the Krakatua

v o l c a n o t h a t c o l l a p s e d i n 1 8 8 3 .


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A NO A A s h i p s u r v e y s a n A l a s k an b a y .


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A tsunami of frightening size happened inLituya Bay, Alaska in 1958. The local tsunami

was caused by a tremendous landslide of more

than 90 million tons of rock that slid into thebay. The tsunami that followed reached 1720feet (by comparison, the Empire State Buildingis 1250 feet tall) up the slope on the opposite

side of the bay.Two fishermen that had anchored their boat

in the bay were killed. Fisherman aboard twoother boats, anchored further away, amazinglysurvived by riding over the wave.

1958 ALASKA TSUNAMI


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TSUNAMI WARNING!

Large tsunamis are too powerful to bestopped, but is it possible to predict them? Insome cases, scientists can make usefulpredictions about where and when a tsunami

might strike. The National Oceanic and Atmospheric Administration (NOAA) operatestwo tsunami warning centers—The PacificTsunami Warning Center (PTWC) in Hawaii and

the West Coast and Alaska Tsunami WarningCenter (WC/ATWC) in Alaska. Plans for a

larger, global tsunami warning system arealso being considered.


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Ts u n a mi s u r v i vo r s s ea r c h f o r a n y p e r s o n a

l

b e l o n g i n g s t h e y c a n s a l v a g e .

The Pacific Tsunami WarningCenter in Ewa Beach, Hawaii.


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Scientists at the centers monitorseismographs to detect undersea earthquakes.

They also monitor ocean buoys and otherinstruments planted on the sea floor for signsthat a tsunami is on the move. The tsunami

warning centers notify regional and localauthorities whenever a tsunami threatens.

Tsunamis are possible in just about any largebody of water, but they are most common inthe Pacific Ocean. Many Pacific coastalcommunities from California to Alaska andHawaii have tsunami education programs andpre-planned evacuation routes.

1960-Chile:

In 1960, thelargestearthquake everrecorded rockedSouth America.The quake wascentered off thecoast of Chile.

Within 15minutes,devastatingtsunamis slammedinto the Chileancoast destroyingeverything intheir path.Thousands ofpeople werekilled. Theretreating wavespulled many outto sea. Tsunamiwaves caused bythe same quakestruck Hawaii 15hours later.Sixty-one peoplewere killed inHilo, Hawaii.


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One reason tsunamis are so dangerous is thatthey are not common events. People do notexpect a tsunami as they might expect bad

weather. Most people have never experienced atsunami, so when faced with one, they are unsurehow to react.

Tsunamis will always be a threat for peopleliving on the coast. However, disasters like the

one in the Indian Ocean in 2004 do not have tobe so deadly. Early warning, education, and quickevacuation can save lives.

TAMING THE WAVE


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Mo s t o f u s w i l l n e v er h a v e t o f a c e a de

a d l y t s u n a mi .

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buoys (BOO eez) — floating devices used to takemeasurements

displacement (dis PLAYS ment) — change in position

earthquakes (URTH kwayks) — sudden shaking of the earthcaused by shifting rock inside the earth

landslides (LAND slidez) — sudden movement of earth androck down a mountain or hill

magma (MAG muh) — melted rock below the earth’s surface

meteorite (MEE tee ur rite) — piece of rock or metal that fallsfrom space and lands on earth

seismographs(SIZE muh grafs) — instruments that detectand measure earthquakes

seismologists (size MAHL oh jists) — scientists whostudy earthquakes

GLOSSARY


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INDEX


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Alaska 23, 27

Chile 27distant tsunami 8earthquake 8, 15, 27Hawaii 27Krakatau 20landslides 8, 19, 23Lituya Bay 23local tsunami 8mega-tsunami 8micro-tsunami 8NOAA 24

Prince William Sound 15

Sumatra 16tidal wave 8tide 8

volcanoes 19, 20 weather 4, 28

INDEX

David and Patricia Armentrout have written many nonfiction

books for young readers. They have had several bookspublished for primary school reading. The Armentrouts live inCincinnati, Ohio, with their two children.

ABOUT THE AUTHORS

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