^Îit%âVVf^ïn- •':i} 1̂̂

f-^

Studying Volcanoes 4 f

What is a Volcano? 6

Moving Earth 8

Earth Erupting 10

Inside a Volcano 12

Near Volcanoes 14 Ir^

Scary Science 16

Volcano Science 18

Surfing Our Earth 20

Science in Action 21

What Have You Learned? 22

Words to Know/Index 24

Í ••' f

Studying VolcanoesAn erupting volcano is a sight to see. When a volcanoerupts, gases and dust fly into the sky. Falling ash andred-hot lava cover large areas. These materials candestroy everything they touch. An erupting volcanocan put people who live nearby in great danger.

Volcanoes erupt because of powerful forces at workdeep inside Earth. Scientists are not sure what causesthese forces to occur. They study volcanoes to solvethis mystery.

• Kilauea is a volcano located on the southernmost islandof Hawai'i. It is one of Earth's most active volcanoes.

Volcano FactsDid you know that the circular, funnel-shapedopening at the top of a volcano is called a crater?Read on to learn more about volcanoes, lava, andvolcanic eruptions.

• Materials spurting out of a volcano are very hot.They are about 2,000° Fahrenheit (1,093° Celsius).This is hot enough to cook a hot dog in one second!

• Lava can travel 120 miles (193 kilometers) per hour.

• Lava is magma that has come to Earth's surface.Thereare two kinds of lava. Fluid lava, called pohoehoe, flowsquickly. Sticky lava, called a'a, moves more slowly.

• Earth's largest volcano is Mauna Loa. It rises 2.5 miles(4 km) above sea level. Mauna Loa covers about halfof the island of Hawai'i.

• Volcanoes helped create Earth.They added newrock to the land and gases to the atmosphere.

• Some people choose to live near volcanoes.This isbecause the land is good for farming.

What is a Volcano?A volcano is an opening in Earth's surface. Magmaand gas rise through the opening and burst forth.The opening is usually found at the top of a cone-shaped mountain. These mountains are often calledvolcanoes, too.

Volcanoes are not all the same. They can look verydifferent. Layers of magma form volcanoes. Thesize and shape of a volcano depend on the magma'sthickness. The type and timing of eruptions alsochange how volcanoes look.

\

• Crater Peak is on Mount Spurr in Alaska. It began eruptingat least 6,000 years ago.

Types of VolcanoesScientists group volcanoes into three main types.The types are cinder cones, composite volcanoes,and shield volcanoes.

Cinder cones are steep and cone-likeJ^ in shape.They are formed from tiny,

' ' 'v glassy pieces of volcanic rock.Thesepieces settle around the vent.

__ Composite volcanoes are also cone-shaped.They are larger than cindercones because they have eruptedmany times from the same vent.

Composite volcanoes are made from alternating layersof lava, volcanic ash, and cinders. Cinders are pieces ofcoal, wood, or other material that is still hot and glowingbut no longer burning.

Shield volcanoes look like largemounds.They are formed by fluid

.̂ I lava made of basalt.This kind of«,. r . ' /.' lava flows quite far. It creates soft-sloped mountains.

Moving EarthEarth's surface is made of a thin layer of rock calledthe crust. The crust is broken into twelve large piecescalled tectonic plates. A river of hot magma flowsunder the plates. The movement of the magma causesthe plates to slowly shift. Sometimes the plates moveaway from each other. Sometimes they hit againsteach other. Volcanoes can occur as a result of thisunderground movement.

• The Pacific Plate is the largest tectonic plate. It is nearly9,000 miles (14,484 km) wide.

Locating VolcanoesMost active volcanoes are found around the PacificOcean.The volcanoes form a pattern along theedges of the tectonic plates. As a group, thesevolcanoes are called the "Ring of Fire/'

There are 1,500 active volcanoes above sea level. Notall volcanoes are above sea level. Most of the world'svolcanoes are under the sea. Some underwatervolcanoes grow over time.Their size increasesas new layers of lava harden on top of old layersof lava. Underwater volcanoes can break throughthe water's surface.They form islands.This is howthe Hawai'ian Islands formed.

Earth EruptingEarth's interior is extremely hot. It is so hot that rockcan melt. As rock begins to melt, gas is released. Thisgas mixes with magma. The gas makes the magma solight that it rises to Earth's surface. The magma collectsin a chamber under the volcano.

As more and more magma enters the chamber, pressurebuilds. The heat of the magma melts or breaks througha weak part of the chamber. The magma eventuallybursts through Earth's surface via this passage. Overtime, other vents will appear in the mountain.

• The amount of gas in magma affects an eruption.Themore gas there is in magma, the more violent the eruption.

Kinds of EruptionsThere are different ways that volcanoes can erupt.Some eruptions are very powerful and scary. Othersare weak and less scary.

Explosive eruption: Some eruptionseject liquid and partly solid lava andpieces of rock.These eruptions arecalled explosive eruptions. Sometimesthese eruptions can last several hours.Sometimes they last for days.

Nonexplosive eruption:Nonexplosive eruptions usuallyoccur in Hawai'ian volcanoes. Lavaleaks through the sides of a volcano.The lava flows, destroying everythingin its path.

Active volcanoes have erupted in the past few hundredyears. If a volcano has not erupted for a few hundredyears, but has erupted in the last several thousandyears, it is called dormant. An extinct volcano is avolcano that has not erupted for several thousand years.

Inside a VolcanoHave you ever imagined looking inside a volcano?This would be very dangerous. Scientists havestudied volcanic rocks and Earth's surface.Theyhave even studied volcanoes on other planets.They have discovered that all volcanoes sharesome common features.

Secondary Vent

Crust

Ash, gas, and cloud

Vent

\

Crater

Lava

Magmachamber

Near VolcanoesImagine living near a volcano. Maybe you do.Mount St. Helens is located in Washington State.This mountain is near the Pacific Coast. It is partof the Ring of Fire, Mount St. Helens erupted onMay 18, 1980. A huge explosion spewed gas andash 12 miles (19 km) into the air. Fifty-sevenpeople died. Many plants and animals were alsokilled. A large piece of the mountain tore off.

• Before Mount St. Helens erupted in 1980, it was 9,760 feet(2,975 m) tall. After, it was 8,525 feet (2,598 m) tall.

Volcano HazardsWould you be afraid to live beside an active volcano?People who live near active volcanoes face manyfrightening hazards.

Ash and dustAsh and dust can cover large areas.They can destroycrops and plant life.They can also kill people.

Lava flowsSome types of lava flow very quickly. People do notalways have time to leave the area. Hot lava can kill.

Volcanic gasesGases are released into the atmosphere during aneruption.These gases can be poisonous. Peoplemay die if they breathe in the gas.

MudflowsMudflows caused by an eruption are known aslahars.They are caused when rain mixes withash. Lahars destroy everything in their path.

Tidal wavesUnderwater volcanoes cause tidal waves.These wavesare called fSL/nam/s.Tsunamis can flood coastal areasand kill people.

Scary ScienceVolcanologists study volcanoes. Their work canbe dangerous. Sometimes volcanologists studyactive volcanoes. They have to wear special clothing.Insulated suits protect their skin from the heat.

Why would a person choose such a dangerous job?Studying volcanoes is important. Volcanologistscan predict eruptions. What they learn can save lives.

• It is important for volcanologists to study geology.Geology is the study of Earth's rocks.

Special RocksVolcanoes are not always harmful. They can creategood soil for farming. They also produce volcanicrock, which can be valuable.

Volcanic rock forms whenlava hardens. Volcanicrock is igneous rock.There are different àtypes of igneousrock.This is becausethere are differentkinds of lava. Someof the best-knownigneous rocks arebasalt, granite, pumice,and obsidian.

Basalt is the most common type of igneous rock. Itis used to build roads. Granite is used in construction.People use pumice to scrub away dry skin. Obsidianlooks like black glass and is used in jewelry. Sometimesprecious stones are found in igneous rock. Such stonesinclude diamonds, rubies, and opals.

Volcano ScienceVolcanologists use different methods and equipmentto study volcanoes. They track volcanic activity usingobservatories and maps. They study volcanic rockin laboratories.

An important tool used to study volcanoes is aseismometer. This tool measures tremors in theground and helps predict volcanic eruptions.Volcanologists also use lasers to record changesin the ground around volcanoes. This gives cluesabout volcanic activity.

• Seismographs are used to predict volcanic eruptions,A seismograph measures and records Earth's vibrations.

Explosive MythVolcanoes are named after Vulcan, the Roman godof fire. Early Romans believed that Vulcan livedbeneath Vulcano Island.

Early Romans found a smoking island off the coastof Sicily. They believed the god of fire made lightningdeep inside.They named the island Vulcano.The islandis still there today.

Surfing OurEarth

How can I find more informationabout volcanoes?

• Libraries have many interestingbooks about volcanoes.

• Science centers are great placesto learn about volcanoes.

•The Internet offers some greatWeb sites dedicated to volcanoes.

Where can I find a good reference Website to learn more about volcanoes?Encarta Homepagewww.encarta.com

• Type any volcano-related term into the search engine.Some terms to try include "tectonic plates" and "volcano."

How can I find out more about volcanoes andrecent eruptions?U.S. Geological Survey Volcano Hazards Programhttp://volcanoes.usgs.gov

• This Web site offers video clips of erupting volcanoes, avolcano glossary, and the latest news on volcanoes aroundthe world.

Science in ActionMake Your Own VolcanoThis activity should be done withan adult.

You will need:• a foam tray• a cone-shaped party hat• an empty film canister' papier-mâché• 1 tablespoon (15 mL)

baking soda• vinegar, dyed with red food coloring

Directions:• Place the foam tray on a table covered with newspapers.' Cuta hole in the top of the party hat. Fit the film canister snugly

into the hole.• Set the hat on the tray. Be sure the opening of the film canister

faces the ceiling.' Cover the hat and tray with papier-mâché. Do not cover the

opening of the film canister. Let the volcano dry overnight.• Put the baking soda into the top of the volcano.' Poke a few holes in the baking soda with a toothpick. Pour red

vinegar into the top of the volcano.• Watch your volcano erupt!

What Have You Learned?

What is the name for theqroup of voUanoes foundalong the pacific ocean?

What is thename of Earth'slargest volcano?

What ismagma calledwhen it isoutside ofa volcano?

What kindof volcano isformed by aneruption ofbasalt lava?

What is a scientistwho studiesvolcanoes called?

What is thename forvolcanic rock? r/ There are two types

of volcano hazards.True or false?

What toolis used tomeasurevolcanictremors?

- —What is thename formudfiows causedby an eruption?

y *oi

oueD|OA p

sno9uß| "9V'S oue3|OAeo-| euneiAi '£

I :sjaMsuv

Wordsatmosphere: air, a mixture of gases

surrounding Earth

basalt: a type of volcanic rock thatis hard, black, and often glassy

erupting: ejecting gas, steam, ash,or lava out of a volcano withgreat force

insulated: prevented heat fromcoming through

lasers: devices that make very thinand strong beams of light

lava: hot, melted rock that comesout of an erupting volcano

magma: very hot liquid rock deepinside Earth

observatories: places that havetelescopes used for studying,the Sun, the Moon, planets,and stars or volcanoes

predict: guess based onspecial knowledge

tremors: shaking

vent: an opening from which gasesor volcanic material escapes

ash 4,7,13,14,15

crust 8,12

dust 4,15

Earth 4,5,6,8,10,12,

16,18,20eruption 5,6,10,11,

14,15,16,18,20

gas 4,5,6,10,13,14,15

Hawai'i 4,5,9,11hazards 15,20

lava 4,5,7,9,11,13,15,17

magma 5,6,8,10,13Mauna Loa 5

Mount St. Helens 14

Ring of Fire 9,14rock 5,7,8,10,11,12,

16,17,18

tectonic plates 8,9,20

vent 7,10,12,13volcanologists 16,18Vulcan 19