geology of the pacific northwest (gnv64)

7/27/2019 Geology of the Pacific Northwest (Gnv64)

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of the

PacificPacificNorthwestNorthwest

BUILD IT

YOURSELF

SERIES

Investigate How the Earth Was Formed

with15PROJECTS

CYNTHIA LIGHT BRO


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Illustrated by Eric BakerCYNTHIA LIGHT BROWN

of the

PacificPacific

NorthwestNorthwestInvestigate How the Earth Was Formedwith15

PROJECTS


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Nomad Press

A division of Nomad Communications

10 9 8 7 6 5 4 3 2 1

Copyright 2011 by Nomad Press. All rights reserved.

No part of this book may be reproduced in any form without permission in writing from

the publisher, except by a reviewer who may quote brief passages in a review orfor limited educational use.

The trademark Nomad Press and the Nomad Press logo are trademarks of Nomad Communications, Inc.

This book was manufactured by Sheridan Books,Ann Arbor, MI USA.

May 2011, Job # 325132

ISBN: 978-1-936313-38-9

Illustrations by Eric Baker

Questions regarding the ordering of this book should be addressed toIndependent Publishers Group

814 N. Franklin St.Chicago, IL 60610www.ipgbook.com

Nomad Press2456 Christian St.

White River Junction, VT 05001www.nomadpress.net


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Nomad Press is committed to preserving ancient forests and natural

resources. We elected to print Geology of the Pacific Northwest: Investigate

How the Earth Was Formedon 4,507 lbs. of Williamsburg Recycled 30

percent offset.

Nomad Press made this paper choice because our printer, Sheridan

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~Titles in the Build It YourselfSeries~


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GLOSSARY RESOURCES INDEX

INTRODUCTIONGeology and Geography 1

CHAPTER 1Plate Tectonics Shape Our Land and Sea 5

CHAPTER 2Mountain Ranges 17

CHAPTER 3

Volcanoes and Earthquakes! 30

CHAPTER 4Basins and Plateaus 47

CHAPTER 5Climate 59

CHAPTER 6Rivers 72

CHAPTER 7Ecosystems 87

CHAPTER 8The Coast 100


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Geology & Geography

he Pacific Northwest is a land of exciting contrasts.

It has the largest annual snowfall in the world. Ithas rainforests, and it has deserts. Te Pacific Northwestalso has some of our nations greatest natural wonders,such as the mighty Columbia River, majestic DenaliPeak, and rugged Glacier National Park.

How did these amazing landscapes form? Why are they so differentfrom other parts of the country? Most of the Pacific Northwest wasnt

even part of the original North American continent, but was stitchedtogether like a patchwork quilt. Tat stitching is still going

on, which causes explosive volcanoes andrumbling earthquakes.

1

INTRODUCTION


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GEOLOGY OF THE PACIFIC NORTHWEST

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Geology and Geography

In this book, youll learn about thegeology and physical geography ofthe Pacific Northwest. Youll read about

the great forces that have shaped theregions mountains, rivers, weather, andecosystems. Youll also come acrosssome interesting trivia facts.

Did you know that the highestmountain in the United States is in thePacific Northwest? And that the regionholds the United States record for the

largest temperature change in one day? Asyou read through this book, youll get towork on a lot of exciting experiments andprojects. Tey will help you understandthe concepts better, like how fog formson the West Coast.

Geology: More Than Just Rocks

Most people think of geology as the study of rocks. It certainly includesthat, but its much more. When you look at a rock, you can describeits color and shape. But what is even more interesting is how that rockformed and how it got to its present location. Tat involves seeing thebig picturethe picture of the whole earth.

Geology is the scientic study of the history and physicalnature of the earth. It explains how the color and shape

of a rock gives clues to the history of that rock.

Geology involves the huge movements of the earths crust. It alsoinvolves the systems of the atmosphereand hydrosphere, becauseair and water affect the breakdown and formation of rocks. And thegeology of the Pacific Northwest tells an exciting part of that story.

Words to KnoW

geology:the scientific study of

the history and physical nature ofthe earth.

geography:the study of theearth and its features, especially theshape of the land, and the effect ofhuman activity on the earth.

ecosystem: a community ofplants and animals living in thesame area and relying on eachother to survive.

atmosphere:the airsurrounding the earth.

hydrosphere:the earths water,including oceans, rivers, lakes,glaciers, and water vapor in the air.

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Geography:

More Than Just States and Capitals

Just as geology is about more than just rocks, geography is about morethan just states and their capitals. Tese are important, but geographytells a bigger story.

Tere are two parts to geography. Physicalgeography includes things like mountains,rivers, climate, and the shape of the land.Te second part of geography is how peopleinteract with the land. Tis is called cultural

geography and it includes things like population, agriculture, andrecreation. An example of cultural geography would be how peopleaffect the flow of a river by building dams or cities on it.

Te geography of the Pacific Northwest includes a lot of sprawlingmountain ranges. Tis makes the borders of the region hard to define.For example, the northern Rocky Mountains cover Idaho, but they alsoextend into western Montana. Te Cascade Mountains run through thestates of Washington and Oregon, but also into the very northern partof California.

This book covers all of the states of Washington, Oregon,Idaho, and Alaska, as well as western Montana and thenorthern section of California. It focuses on the geology

and physical geography of the Pacic Northwest.

Are you ready to explore the thunderingwaterfalls, active volcanoes, and surging

glaciers of the Pacific Northwest? Tenlets go and visit this incredible land ofbeauty and adventure!

Words to KnoW

climate: the averageweather of an area over along period of time.

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Geology and Geography

Our Land and Sea

What is the driving force behind the formation ofthe different landscapes in the Pacific Northwest?

You need to understand plate tectonics.

Plate tectonics is a scientific theory developedin the 1960s. It says that the outer layer ofthe earth is made up of interconnected platesthat are constantly moving around. Volcanoes,mountains, valleys, and earthquakes all happenwhen and where they do because of themovement of the earths plates. o understandplate tectonics, first lets look inside the earth.

Plate Tectonics Shape

Words to KnoW

plate tectonics:thetheory that describes howplates move across the

earth and interact witheach other to produceearthquakes, volcanoes,and mountains.

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CHAPTER 1


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A Peek Inside

Te earth is made up of three main layers.Tey have different chemical compositionsand physical properties.

Te crustis the thin, outer layer of theearth. Tis is the layer that we walk on.Its solid but brittle, which means that itbreaks when under pressure.

Te mantleis the layer below the crust.It is hotter and denser here because the

temperature and pressure inside the earthincrease the deeper you go. Te uppermantle is brittle and solid. ogether, thecrust and the upper mantle form thelithosphere, or the hard outer layer ofthe earth. Te lithosphere is broken intoplates. Below the plates is a layer calledthe asthenosphere. It is partially molten

and can flow slowly without breakingabit like Silly Putty.

Te coreis the center of the earth. Itis extremely dense and made up of iron and nickel. Teres an innercore, which is solid because the pressure is so great, and anouter core, which is liquid. Tecore is almost as hot as thesunabout 9,000 degreesFahrenheit (5,000 degreesCelsius)!

Words to KnoW

crust:the thin, brittle, outer layer

of the earth. Together with the uppermantle, it forms the lithosphere.

brittle:describes a solid thatbreaks when put under pressure. Ablade of grass will bend, but a drytwig is brittle and will break.

mantle:the middle layer of theearth. The upper mantle, togetherwith the crust, forms the lithosphere.

lithosphere:the rigid outer layerof the earth that includes the crustand the upper mantle.

asthenosphere:the semi-molten middle layer of the earth thatincludes the lower mantle. Much ofthe asthenosphere flows slowly, likeSilly Putty.

core: the center of the earth,composed of the metals iron and

nickel. The core has two partsasolid inner core, and a liquid outercore.

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Plate Tectonics Shape Our Land and Sea

The Earths Puzzle

Te hard outer layer of the earth, the lithosphere, is broken up into about12 large sections, called plates. Tere are alsoseveral smaller plates. Te plates fit togetherlike a jigsaw puzzle. Most of the plates are partoceanicand part continental. For example,the North American Plateincludes nearly allof North America and the western half of theAtlantic Ocean.

Te plates are in constant slow motion! Tats because the layer just

under the platesthe asthenosphereis very hot. Te heat causes themolten rocks there to move around in huge

rotating currents called convection cells.Tese convection cells move the plates

above, which are floating like raftson the hot goo below. Te platesalso help themselves move along.

Te older part of a plate is colder and

denser. When it sinks into the mantleit pulls the rest of the plate with it

and keeps the cycle going. Plates movesomewhere between 1 to 6 inches per year

(2 to 15 centimeters).

On the Edge

Volcanoes and earthquakes dont just happen anywhere. Teyre arranged

in patterns. For example, there are lots of volcanoes around the rim ofthe Pacific Ocean, but there are none in Kansas. Tats because most ofthe action happens where one plate meets another. Tis is called a plateboundary. Tere are three different kinds of plate boundaries.

Words to KnoWoceanic:in or from theocean.

continental:relatingto the earths large landmasses.

You might haveheard of the earths

plates being sections ofthe earths crust. Thats partlycorrect. The tectonic plates are

made of the crust and the upper

mantle, which together are calledthe lithosphere. But mostpeople just call it the crust

because its easier toremember.

Did You Know?

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Divergent plate boundariesare wheretwo plates move apart from each other. Teydo this because the hot molten goo beneath,

called magma, is pushing upward. Tis causesrifting. Te hot goo pushes out and solidifiesto form new rocks. Nearly all of the earthsnew crust forms at divergent boundaries. Anexample of a divergent boundary is about 280miles off the coast of Oregon and Washington(450 kilometers). Rifting is occurring there atthe Juan de Fuca Ridge.

Convergent plate boundariesare wheretwo plates collide. What happens depends onwhether the plates are oceanic or continental.

One type of collision is when an oceanicplate collides with a continental plate. Because the oceanic plate isdenser and thinner than the continental plate, it slides underneath thecontinental plate. Tis is called subduction.

As the subducted oceanic plate sinks lower, its weight pulls the restof the plate along as well. Te sinking plate encounters a lot of heat andpressure. Tis causes the plate to release hot gas and steam, which risesand melts the rock above. Te melted rock, the magma, alsorises to the surface, creating volcanoes.In the Pacific Northwest, this ishappening right now to createthe Cascade Mountains

with explosive volcanoeslike Mount St. Helens.

Words to KnoW

divergent boundary:

where two plates are moving inopposite directions, sometimescalled a rift zone. New crust formsat rift zones from the magmapushing through the crust.

magma:partially melted rockbelow the surface of the earth.

rifting:when the lithospheresplits apart.

convergent boundary:

where two plates come together.

subduction:when onetectonic plate slides underneathanother tectonic plate.

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If a continental plate collides with anothercontinental plate, they both buckle upwards,forming mountains. Tats what is happening

now where the Indian Plate and the EurasianPlate are colliding. Te result is the HimalayaMountains, which include the highestmountain in the world, Mt. Everest. Longago, the Brooks Range in northern Alaskaformed when continental crust slammed intoNorth America.

Transform plate boundaries are where two plates grind againsteach other as they move side by side in opposite directions. As the platesmove past each other they sometimes suddenly slip. Tis creates a biglurch, or earthquake. Te famous San Andreas Fault in California ispart of a transform boundary between the North American and PacificPlates. Tis is why California has so many earthquakes. A transformboundary also runs through Denali National Park in Alaska.

Hotspotsare areas of strong geologicactivity, but they arent on the edge ofplates. Hotspots are small, extremelyhot regions that usually occur in themiddle of a plate. Tey exist becausehot material, probably from deep in themantle, makes its way to the surface.Te Hawaiian Islands formed when thePacific Plate slowly made its way overa hotspot. Teres also a hotspot thatis now beneath Yellowstone NationalPark, located where Wyoming, Idaho, and Montana meet.

Words to KnoW

transform boundary:

where two plates slideagainst each other.

hotspot:an area that canbe found in the middle of aplate, where hot magma risesto the surface.

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Tectonic History of the

Pacif ic Northwest

Te Pacific Northwest has had avery active tectonic history. Terocks often record this history,

but it can be hard to sort out whathappened when. And sometimesrocks have been completely removeddue to erosionor subduction. As youmight guess, the farther back in timeyou go, the harder it is to tell whathappened. Nevertheless, geologistshave pieced together a rough picture

of the tectonic past.

Words to KnoW

tectonic: relating to the forces

that produce movement andchanges in the earths crust.

erosion:when a surface isworn away by wind or water.

geologists:scientistswho study the earth and itsmovements.

algae:plants that live mainly inwater. They do not have leaves,roots, or stems.

sediments:loose rockparticles such as sand or clay.

Giant Conveyor BeltThe movement of the plates acts a bit like a giant, wide conveyor belt. This conveyorbelt is like a flat escalator, used to move people or things across a long space. Atdivergent boundaries, magma pushes through, cools, and forms new crust.

The lithosphere is like a rigid board, though, and as two plates move apart, theother end of each plate collides with another lithosphere. At the collision, one plateis subducted, or pushed under, and melts. So lithosphere is created on one end,and destroyed on another. Just like conveyor belts, or the stairs on an escalator,lithosphere appears on one end and disappears on the other end.


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A Big BasinWhen Rodinia started to break apart, a large basin started forming where thewestern border of Idaho is today. Huge piles of sedimentsbuilt up in the basin.

At places, these piles of sediment were 13 miles thick (21 kilometers)!

Today, rocks formed from these sediments are known as Belt rocks (named afterBelt, Montana). You can find them in western Montana and northeastern Idaho.Glacier National Park has Belt rocks exposed in its beautiful mountains.

About a billion years ago, all the continents on earth were assembledinto a single continent surrounded by one giant ocean. Tis hugesupercontinent has been named Rodinia. It was a bleak place. Te only

plants were single-celled algae. Tere were no animals. And there wereprobably huge storms.

About 750 million years ago, Rodinia brokeapart. Te rift was about where the western edgeof Idaho is today, and as the continent pulledapart, an ocean formed. Te east side of therift is now Idaho and western Montana. Someof the oldest rocks in the Pacific Northwest

region can be found here. Most of what we nowknow as Washington and Oregon didnt exist then!

Millions of years passed, and a new supercontinent slowly formed.Scientists called this new supercontinent Pangaea. About 200 millionyears ago, Pangaea also broke apart and the Atlantic Ocean began toform. Tat pushed the North American Plate westward, where it collidedwith an oceanic plate. Tis oceanic plate began subducting beneath the

North American Plate.

Rodinia is aRussian word that

means homeland.Pangaea is a Greekword that means

all lands.

Did

You

Know?

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But the oceanic plate had lots of accumulated sediments on top of it.So when the oceanic crust was pushed under the North American Plate,the sediments were scraped off and they stuck onto the continent. Tere

were also volcanoes forming from the subduction. Over many millionsof years, other rocks were jammed onto the continent. All of these rockseventually became Washington and Oregon.

Between 7 and 4 million years ago, the subduction became steeper.Tis means that the subducting plate pushed down at a steeper angle,and it caused the continental edge to fold. Te Olympic Mountains areon the crest of that fold.

AlaskaAlaska is even more complicated.Geologists think that only about 1percent of Alaska is originally fromthe North American continent.Te rest is a mixed-up crazy quiltof rock groups that have foundtheir way into this beautiful and

interesting land.

Some of these rock groups areold continental crust. Others areoceanic rocks. Some rocks formednearby and some are from greatdistances. Te movement of theplates has jammed one rock group

after another onto the continentto slowly form Alaska.

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Whats Happening Now?

Right now, about 280 miles (450 kilometers) off the coast ofWashington and Oregon, there is adivergent plate boundary where twooceanic plates are moving apart fromeach other. Te plate on the easternside of the boundary, the Juan deFuca Plate, is being pushed farthereast, where it is colliding with thecontinental North American Plate.And what happens when an oceanicplate meets a continental plate? Downit goes!

As it subducts, this oceanic platepartially melts, forming magma, andreleasing lots of gas and steam. Tisis where the Cascade Mountains haveformed. Because the subduction is still

going on, there are many active volcanoesin the Cascades. Te last major eruption from a Cascade mountainvolcano was Mount St. Helens in 1980.

Subduction also causes earthquakes as the two plateslock together, then nally release with a lurch.

Meanwhile, in Alaska, another oceanic plate is subducting beneaththe North American Plate. Tis is forming the volcanic mountains thatare the Aleutian Islands. Teres also a huge block of land that has beentransported 375 miles in the last 30 million years (603 kilometers). Asits being jammed against the continent, its creating Alaskas CoastalMountains about 10 miles from the coast (16 kilometers).

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1Cut one end from thelayered candy bar

just enough to seeinside. This is calledthe cross-section of thecandy bar. How are thelayers like the layers inthe earth?

2

Using the knife,make two or

three cracks in thechocolate across thetop middle part of thelayered candy bar.The chocolate on eachside of the cracksrepresents differentplates. Grab the candybar on each end andslowly pull apart,

about one inch or less.What does the gooeylayer underneath do?This represents theasthenosphere, whichis soft and stretches.The pulling apartrepresents a divergentplate boundary.

Sweet Plate Boundaries

SupplieS

candy bar with layerssuch as a Milky Way

table knife(one that isnt sharp)

solid chocolate candybar

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3 Push the layers backtogether, then pushone side away from you

and pull the other sidetowards you. Do youfeel resistance? Thisrepresents a transformplate boundary, whenplates grind together.

4 Take half the layeredcandy bar in one hand,and the solid chocolatebar in the other hand.Pretend the layered bar isa continental plate whilethe solid bar is an oceanicplate.

5 Push the two candybars together, lettingthe solid chocolate

bar go underneath thelayered candy bar. Thisrepresents a convergentboundary, where twoplates collide. The oceanicplate subducts beneaththe continental plate.

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GEOLOGY OF THE PACIFIC NORTHWESTGEOLOGY OF THE PACIFIC NORTHWEST

Plate Tectonics: The Original RecyclerThe earth has been recycling materials for over 4 billion years! Every rock that yousee has come from another kind of rock. And every rock that you see will eventuallybecome another one. All this recycling is because of the movement of the platespushing everything around. To understand this recycling, first you have to know abit about types of rocks.

There are three main types of rocks: igneous, sedimentary, and metamorphic.

Igneous Rockshave formed from the cooling of molten rock. As you go deeperbeneath the surface of the earth, it becomes hotter. At around 25 miles beneath thesurface, its hot enough to melt rocks (40 kilometers). When that molten rock, called

magma, comes to the surface, it cools into igneous rocks.Sedimentary Rocksform when small particles of rock, called sediments, arepressed tightly together into rock. Sediments come from other rocks being eroded,or broken into smaller pieces by wind, water, ice, and gravity. Sedimentary rockscan also form from the remains of plants or animals being pressed together. When

seawater evaporates, the minerals and salts in the water stay behind and canform into rock.

Metamorphic Rocksform when heat or pressure changes rocksinto new rocks. Pressure, like temperature, increases as you go fartherbeneath the surface of the earth.

If rocks are pushed under the surface, but not far enough to melt, theycan be changed into new rocks without first melting.

Igneous rocks can be eroded into sediments, which then formsedimentary rocks. Those sedimentary rocks can then be

buried and heated and squeezed to form metamorphic rocks.Metamorphic rocks can be pushed down into the mantle andmelted, to later form igneous rocks. Or it could happen in

reverse, because any type of rock can formfrom any other type of rock.

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he Pacific Northwest has some of the most stunningmountains in the world. Tese include the CoastMountains, the Cascade Range, and the northernRocky Mountains. Why did such beautiful mountainsform here?

Northern Rocky Mountains

Te Rocky Mountains, also called the Rockies, are a major mountainchain that runs from New Mexico to Canada. Te northern Rockies arelocated in Idaho and western Montana and form the eastern boundaryof the Pacific Northwest region.

Mountain Ranges

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Te Rockies were formed around 90 millionyears ago. ectonic plates slammed together,causing rocks to fold and push over each

other. In geology, this is called thrusting.In fact, the northern Rockies are called

a fold and thrustbelt because thatshow they formed.

Amazingly, the rocksthat were pushed on topof the Rockies are one

and a half billion years olderthan the rocks underneath! Tese older rocksare unusual because they havent changed much.hey still show original ripple marks, raindropimpressions, and mud cracks. Imagine seeing animpression of a raindrop that fell over one anda half billion years ago! Tese rocks can be seenthroughout western Montana and Idaho, but

are most spectacular in Glacier National Park inMontana.

Words to KnoW

thrusting:when rocksare pushed up and overanother set of rocks.

fold and thrust belt:a belt of mountains that hasformed by one tectonic platesubducting under anotherand causing rocks fartherinland to fold and be thrustover other rocks.

fossils:the remains ortraces of ancient plants and

animals.

glacier: a body of ice that

slowly moves downhill due togravity.

Try This!To get an idea of how the Rockies formed, try placing a book on one end of a

small rug. Then push the book and rug underneath toward the other end of therug along a smooth floor. Does the rug bunch up, creating small folds? Thesefolds are like the northern Rockies.

Some of therocks that have been

pushed on top in thenorthern Rockies have many

stromatolites. These are fossiof blue-green algae that used to in warm, shallow seas. Many of tfossils are very detailed, and all

very oldover 1 billion yearsold. For geologists, its like

looking back in time.

Did

You

Know?

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Mountain Ranges

The Coast Range

In the last chapter, we saw how Washington and Oregon were formedwhen an oceanic plate subducted under the North American Plate. Tatoceanic plate was carrying lots of sedimentary rocks that were scrapedoff and squeezed and mashed and shoved upward to form stunningmountains. Tese mountains are called the Coast Range. It includes theOlympic Mountains to the north in Washington, the Oregon CoastRange, and the Klamath Mountains in southernOregon and northern California.

Along the Coast Range, a peculiar

type of recycling is going on.It begins with a rock high on a

mountain. Over time, this rock is erodedby rain and streams. Te water carriesgrains of sand from the rock out into theocean. Te grains of sand settle onto the oceanfloor, where they very gradually form into rockagain. Meanwhile, the oceanic plate carries the

rock back towards the coast. As the plate pushesunder North America, the rock is scraped off and pushed higher andhigher, until its on top of the mountain again. Te whole process cantake 20 million years or more!

Cascade Mountains

Te Cascade Mountains are some of the most beautiful mountains inthe world. Tey are full of jagged peaks, glaciers, and waterfalls. Te

Cascades extend from southern Canada down through Washington,Oregon, and into northern California. Tey lie in a fairly straight linebecause they run parallel to the coast.

The Cascades

are steep and oftencovered with snow.They have been a barrier

to people throughout history.Native American tribes were so

separated by the mountainsthat different languages

were spoken on theeast and west sides.

DidYou

Know?

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Most of the Cascades are volcanoes, andmany of them are potentially still active.

Tese snow-covered high peaks are like

giants to the surrounding landscapeand have inspired legends. In manyNative American legends, themountain peaks are gods that throw

fire and stones at each other. Eventoday, the mountains are so rugged that

there are huge areas far from civilization.Many people tell stories of a large, ape-

like creature called Bigfoot living in the area.Another name for this creature is Sasquatch.

Mountains of Alaska

Alaska is a huge state, and it has huge mountains. In fact, 17 of the 20highest peaks in North America are in Alaska, including the highest,Denali. Tese mountains contain an incredible array of wildlife,including grizzly bears, caribou, wolves, loons, Arctic terns, moose, and

Dall sheep. Tere are three primary mountain ranges in Alaska.TeBrooks Rangestretches across the entire northern part of the state

from east to west. Tese mountains are wild and pristine. Few people livein them and theyre hard to reach. Te range is so far north that

its above the Arctic circle, which means that snow can fallin any month of the year. It also means that the sun doesnot rise on the shortest days of the year in December,and it does not set on the longest days of the year in June.

Te Brooks Range is home to theArctic National Wildlife Refugein the east and Gates of the Arctic

National Park in the central area.

In 1805, the Lewis

and Clark Expeditionfound the only way to cross

the Cascades was by using theColumbia River. When settlers came

later following the Oregon Trail, manygave up their wagons when they came to

the Cascades, and took boats downthe Columbia River to reach the

coast. Others took crooked,difficult trails over the

mountains.

Did You Kn

ow?

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Mountain Ranges

Te Alaska Rangestretches for about 400miles across the central part of the state (644kilometers). Tese mountains are

rugged and wild.Te range contains

several thousand glaciers that altogetheroccupy more area than the entire state ofConnecticut! Te Alaska Range contains thehighest mountain in North America, Denali.

The word Denali means High onein the Athabaskan Indian language.

Te Coast Mountainsfarther south extenddown along the coast of Alaska and Canada.Some of these huge mountains are only 10miles from the ocean (16 kilometers). Allmountains erode, which keeps them fromgetting too high, but moving tectonicplates are pushing the Coast Mountainshigher more quickly than theyre being eroded.As a result, they are the tallest coastal mountainsin the world.

Some Amazing Mountains

Denali:Also called Mt. McKinley, Denali is the highest mountainin North America at 20,320 feet (6,194 meters). It is located withinDenali National Park, which is larger than the entire state of NewHampshire. From its base to its peak, Denali rises over 18,000

feet (5,486 meters). It has more bulk and more of a rise thanMt. Everest, which starts from a much higher plateau. Andits still rising more than an inch each year!

The CoastalMountains in Alaskaare so rugged that

you often cannot travel byroad from one community toanother. You must go by boat

or airplane. Juneau, thecapital, is built on theside of a mountain!

Did

You

Know?

Words to KnoW

plateau:a relatively

level, or flat area.

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Denali is brutally cold, with temperaturesas low as -40 degrees Fahrenheit (-40 degreesCelsius). It has six glaciers that are over 25 miles

long (48 kilometers).Mt. Rainier:At 14,411 feet (4,392 meters),

Washingtons Mt. Rainier is the highestmountain in the Cascades. It is a volcanicmountain formed from explosive eruptionswith rock that cooled from lava, ash, mudflows, and pumice. Rainier is considered oneof the most dangerous volcanoes in the world

today. Its last eruption was 150 years ago, and itcould erupt explosively again. If it did erupt, the numerous glaciers onRainier would melt and form huge, destructive mud flows.

Mt. Rainier has 26 glaciers, the most of any single mountain inthe United States. Carbon Glacier on the north side has the lowestelevation(3,500 feet) of any glacier in the continental United States(1,067 meters). Mt. Rainiers large network of caves in its glaciers

formed due to hot volcanic gases and steam melting the glacial ice.Mt. Rainier is located within Mt. Rainier National Park, which is

about 50 miles southeast of Seattle (80 kilometers). With its old forests,glaciers, elk, and black bears, Mt. Rainier National Park attracts about2 million visitors each year.

Mt. Hood:At 11,249 feet (3,429 meters), Mt. Hood is the tallestmountain in Oregon and the fourth-highest mountain in the Cascademountain range. Tis explosive volcano last erupted about 170 years ago.

When Lewis and Clark traveled on the Columbia Riverin 1805, they noted a tributary that almost blocked theColumbia due to a large sand bank.

Words to KnoW

lava:magma that has risen

to the surface of the earth.pumice:a light rock fullof air spaces, formed fromsolidified lava.

elevation: a measurementof height above sea level.

continental United

States:all of the statesexcept for Alaska and Hawaii.

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Mountain Ranges

Te river, which they called theSandy River, had lots of sedimentbecause of eruptions of Mt. Hood.Geologists consider it the volcanoin Oregon most likely to erupt in thefuture. Mt. Hood has 12 glaciers that covermost of its upper slopes.

Borah Peak: Tis is the highest mountain in Idaho at12,668 feet (3,859 meters). It is located in a section of the northernRockies. Te mountains are rugged and dry, with little vegetation. Terewas a large earthquake on Borah Peak in 1983.

Glaciers

Glaciers are like rivers of ice. o form, glaciers need two things: lots ofsnow and cold enough temperatures that the snow doesnt all melt inthe summer. Glaciers can vary in size from a patch the size of a footballfield, to a river of ice that is a hundred miles long (161 kilometers). Allof the major mountains ranges in the Pacific Northwest have glaciers.

Mountain Ranges

Highest MountainsAlaska:Denali, also calledMt. McKinley, 20,320 feet(6,194 meters)

Washington:Mt. Rainier,14,411 feet (4,392 meters)

Oregon:Mt. Hood, 11,249 feet (3,429 meters)

Idaho:Borah Peak, 12,668 feet (3,859 meters)

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Snow may seem light and fluffy, but when theres a lot of it, it getsheavy. As snow piles up, it presses down on the snow below, whichbecomes ice. Because of pressure from above, the lower layers of ice

begin to flow slowly like a liquid. In addition, a thin layer of water formsunderneath the ice. Tese two things allow the glacier to move downhill.

Not very fastusually only a few inches eachdaybut over time, it adds up. And sometimes,

glaciers surge, or move fastup to 100 feetin a day (30 meters)!

As a glacier moves downhill, it meltsat the lower elevations where its warmer.

When more snow falls at the top of theglacier than melts at the bottom, the glacier

grows. When less snow falls at the top thanmelts at the bottom, the glacier shrinks.

Glaciers come and go in cycles,depending on the climate.

In the last 2 million years, for example, the glaciers in Glacier National

Park in Montana have formed and melted many times. Te ones theretoday formed many thousand of years ago as the climate became colder,but are shrinking now as the climate becomes warmer.

Even though they move slowly, glaciersare extremely powerful. Tey crush just aboutanything in their pathtrees, rocks, andeven large boulders. As they pick up rocksand other debris, glaciers become rough like

sandpaper. Tis roughness erodes and carvesthe land into U-shaped valleys and sharpmountain peaks.

The Taku Glacierin southern Alaska is

the deepest and thickestglacier in the world outside of

the polar regions. It is 4,845 feetthick (1,477 meters). Bering Glacier,also in southern Alaska, is 118

miles long (190 kilometers),which makes it the

longest glacier in NorthAmerica.

Did YouKnow?

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Mountain Ranges

Here are some things to look for that tell you a glacier has been around:

Grooves and Scratches: As the glacier drags smaller rocks overbedrock below, the smaller rocks scratch them and create grooves.

U-Shaped Valley:River valleys are V-shaped, from the river slowlycutting into the rock.Glaciers follow the pathof rivers because, likerivers, they are seeking thefastest way downhill. Butglaciers are wider, and therocks they carry carve out avalley with a U shape.

Hanging Valley:Whena smaller glacier in a sidecanyon feeds into a largerglacier, the smaller glacierdoesnt cut as deeply as thelarger glacier. After they

melt, the smaller glaciers leave behind smaller valleys high up on themountainsides that look like theyre hanging.

Horns:Tese steep-sided mountain peaks are formed by two or moreglaciers carving from different directions.

Cirques:Tese are large bowls that form at the top, or head, of aglacier. Often the bowl fills with water, forming a small lake.

Moraines:When a glacier melts, the rocks it picked up are dumped

out. Because the glacier acts like a conveyor belt made out of ice, moreand more rocks are dumped out, forming a pile at the bottom and sidesof the glacier. Recent moraines look like just thata pile of rocks. Oldermoraines are covered by soil and plants.

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Some glaciers block rivers and create temporary dams.When these dams eventually break, enormous amountsof water flood out. Tis is called a glacial flood.

In early June 1986, the Hubbard Glacier insoutheastern Alaska moved and blocked offRussell Fiord from the sea at DisenchantmentBay. On October 8, the dam broke. It is thelargest glacial flood in recorded history, withalmost 3,700,000 cubic feet per second rushinginto the sea (105,000 cubic meters per second). Tis flowwas nearly 40 times as powerful as Niagara Falls and more

than twice the largest recorded outflow on the Mississippi River.When was the second-largest recorded glacial lake flood? Same place,different timeAugust 2002. Its a busy glacier!

Boom! Iceberg!When a glacier ends at the ocean, large pieces of ice break off, or calve intoicebergs. They make loud creaking and booming sounds before breaking off. Theblocks of ice can be hugehundreds of feet high. Alaska has numerous calvingglaciers. In Glacier Bay National Park in Alaska, tourists often come to watch icebergsbeing calved. One glacier, John Hopkins Glacier, calves such large volumes of icethat its only safe for boats to come within about 2 miles (3 kilometers)!

Icebergs can be many different colors. White icebergs have lots of air bubbles.Blue icebergs are very dense. Greenish-black icebergs have usually calved from thebottom of the glacier. Icebergs can last for a week or more before they melt in the

ocean. They make a nice resting place for passing birds. And of course what you seeabove the surface of the water is, as the saying goes, only the tip of the iceberg.Most of an iceberg is below the surface of the ocean.

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Mountain Ranges

1Using the table knife,slather the peanut butter

to cover at least 2 inchesof one of the pieces ofcardboard (5 centimeters).The peanut butter shouldbe at least a half-inch thick(1 centimeter).

2

Grab the opposite edgeof the cardboard in one

hand, and the clean pieceof cardboard in the otherhand. Slide the cardboardwith peanut butterunderneath the cleancardboard so that some ofthe peanut butter glomsonto the clean cardboard.Keep pushing. What shapedoes the peanut butter

take?

Whats Happening?The clean cardboard is like

continental crust, and the

peanut butter cardboard is like

oceanic crust with sediments

(peanut butter) on top. As

the oceanic crust slides under,

or subducts, beneath thecontinental crust, the sediments

attach onto the continent. The

sediments often form wedges

of new crust that are folded

over so much that the rocks

are jumbled. The Coast Range

formed in this way.

Folded Mountains

SupplieS

table knife(one that isnt sharp)

peanut butter

two pieces of cardboardat least a few inchessquare

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1Rinse the milk cartonand open the top so it

has a square opening.

2 Fill the carton withlayers of snow orcrushed ice, sprinkling thedirt and small pebbles inbetween the layers. Letthe snow settle and addmore snow and dirt layers

until the carton is full.

3 Fill the lunch bag withabout 2 inches of coinsor other small, heavyobjects (5 centimeters).Close the bag and place iton top of the snow. Placethe carton in the freezerwith the open side up.

4Check the carton everyday or so. If theres

room at the top, take outthe bag, add more snowand dirt/pebbles, andreplacethe bag.

"Glacier"

SupplieS

half-gallon size

paperboard milk carton snow or finely crushed

ice

dirt and small pebbles

paper or plastic lunchbag

coins or other small,heavy objects

freezer

scissors

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5After about a week,take the carton out and

peel or cut the paperboardcontainer away. If youhave trouble releasing thepaperboard, run it underwarm water for a minute.What does the snow looklike? Does it look more likesnow or ice?

Whats Happening?Snow is made of ice crystals.

When it is under pressure

(like from the weight of

the coins), the feathery

snow crystals break down

and recrystallize into solid

ice. You may not have hadenough weight and time for

the snow to completely form

into ice. But in a glacier, the

immense weight of the snow

on top causes all of the snow

underneath to recrystallize

as solid ice.

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On the surface, the Pacific Northwest seems to be agentle land, with fog and mist and snow, and great,silent trees. But underneath, tectonic plates are pushingtogether. Tis causes volcanoesto erupt, earthquakes

to tremble, and tsunamisto crash into beaches.

Volcanoes and

Earthquakes!

CHAPTER 3

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Volcanoes and Earthquakes!

What Are Volcanoes?

Volcanoes are formed when magma comes to the surface. Sometimesthe liquid rock cools before it reaches the surface. When that happens,

it forms rocks such as granite. But whenthe magma comes all the way to the surfacebefore it cools, its called lava, and it comesout through an opening in the earth calleda volcano.

Lava can slowly bubble out of the earthor it can shoot out violently. Whats the

formula for an explosive volcano? Tick lavawith lots of water vapor.

Liquids that are very viscous, like honey,resist flow. Less viscous liquids, like water,flow easily. If youve ever heated up a thicksoup in the microwave, you may have noticedthat thick liquids cansometimes have a

mini-explosion,splattering soup all over the inside of themicrowave. Tick lava can explode inthe same way.

It also depends on how much gas,mainly water vapor, is still in the lavawhen it reaches the surface. Lots ofdissolved gas creates pressure in the lava.Tis makes it more explosive, like a soda canthats been shaken. Gas is more easily trappedin more viscous lava.

Words to KnoW

volcano:a vent in theearths surface through whichmagma, ash, and gases erupt.

earthquake: a suddenmovement in the outer layer ofthe earth that releases stress

built up from the motion of theearths plates.

tsunami: a series of giantwaves caused by earthquakes,explosions, meteors, orlandslides.

viscous:how thick and fluida substance is. Honey is veryviscous, while water is not.

An active volcanois a volcano that has

erupted in recorded history.Geologists think it will erupt

again, probably in the next 200years. A dormant volcano is a sleepvolcano that hasnt erupted in record

history, but could erupt again. Anextinct volcano is one that hasnt

erupted in many thousands ofyears and isnt expected

to erupt again.

Did

You

Know?

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Types of Volcanoes

Tere are four main types of volcanoes,and all of them are represented in thePacific Northwest.

Shield volcanoes are large butlow, resembling a warriors shield lying onthe ground. Tese volcanoes erupt quietly.Tey slowly eject a fluid lava that can flowa long way before it cools.

Stratovolcanoes are also called

composite volcanoes. Tey have a classicvolcanic cone shape and can eruptexplosively. Sometimes stratovolcanoesblow off their tops. Tey also producepyroclastic flows, which are deadlyavalanches of extremely hot gases, ash,and rocks.

Cinder cones are small, steep-sided hills that have a classic volcano shape.

Tey are built up by cinders that wereejected and cooled while flying

through the air. When theyreactually erupting, cinder coneslook like a lava fountain.

Volcanic domes happen

when lava that is too thick toflow oozes out of a volcano.

It slowly builds up into avolcanic dome.

Words to KnoW

shield volcano: a broadvolcano formed from the flowof runny, non-explosive lava.

stratovolcano:a classiccone-shaped volcano withalternating layers of runnylava flows and more explosive

volcanic deposits.

cinder cone: a small,

steep-sided volcano, built upby ash and small cinders.

volcanic dome:a volcanoformed by thick lava oozingout. The lava is too thick totravel far and builds up into adome.

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Its a bit like toothpaste where the capis left off and the toothpaste dries out.Tat might sound slow and boring, but

the pressure can build up and make thesevolcanoes very explosive.

Volcanoes can also form in rift zoneswhere tectonic plates are pulling or riftingapart. Te crust cracks, and magma pushesout. Rift zones often produce flat, thick

plateaus of cooled lava.

Pacific Northwest

Volcanoes

In the Pacific Northwest, manyvolcanoes have formed because of thePacific Plate pushing under the NorthAmerican continent. Te Cascadeshave over 2,300 volcanoes that haveerupted in the last 2 million years. TeUnited States Geological Survey closelymonitors 13 of these volcanoes because theyare considered a threat.

Alaska is also full of volcanoes. Morethan 40 volcanoes have erupted since themid-1700s, and up to 100 volcanoes have

erupted in the last 2 million years. AlaskasAleutian Islands are a chain of more than300 small volcanic islands.

In 1989 a jet airplanewas flying over an active

volcano called Mount Redoubtin western Alaska. The volcano

started erupting and spewed an ashplume 45,000 feet high (13,716 metersThe ash melted as it hit the hot engines

coating them with glass. The engines

stopped and the plane startedfalling. Luckily, the pilots were

able to restart the enginesjust before crashing.

Did

YouKnow?

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Here are some of the best-knownvolcanoes in the Pacific Northwest:

Mount St. Helens erupted on May 18,

1980, in the deadliest and most destructivevolcanic eruption in United Stateshistory. Tis large, stratovolcano locatedin Washington is part of the CascadeMountains. Its catastrophic eruption causedan enormous landslide and killed 57people. rees, bridges, railways, highways,

and homes were destroyed for hundreds of miles around.

As early as 1978, members of the U.S. Geological Survey began tosee signs that the volcano might erupt soon. Tey began closelymonitoring the volcano. In 1980, a 450-foot-high bulge developed onthe north side of the volcano. Tis told geologists that magma was

building up. On March 27, 1980, steam began eruptingfrom the volcano and people were

evacuated.

Tere was an earthquake onMay 18, 1980, at 8:32 a.m.Seconds after the earthquake,the bulge broke loose,

causing the largest landslide inrecorded history. An explosive

blast of steam, hot gas, rock,and bits of lava screamed

down the volcano at 680 milesper hour (1,100 kilometers).

Tats faster than a jet airplane!

Words to KnoW

landslide: rock and

earth sliding down a slopedue to gravity.

lahar:a mudflow thatforms from lava and ashmixing with melted snowand rain. It can wipe outeverything in its path.

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A cloud of ash rose 15 miles into the sky(24 kilometers) for nine hours. Te dayturned dark, and ash was carried across

the western United States.

Te hot lava and gas melted thesnow, and mixed together with rock.Tis lahar raced down the side ofthe volcano and destroyed 200 homes.So much mud flowed down the ColumbiaRiver that 31 ships were stranded in ports onthe river.

Mount St. Helens is still active, with much smaller eruptions occurring.Te last eruption started in 2004 and lasted about four years. In 1982,the Mount St. Helens National Volcanic Monument was established forresearch, recreation, and education.

Alaska Airlines

has lots of experienceflying around ash clouds in

Alaska and Washington. Theyhave developed computer modelsto tell where ash from volcanoes

will go. Airplanes fly at least35 miles away from

ash clouds.

DidYou

Know?

Try This!Ask an adult for permission to try this experiment. Get two cans of soda. Open oneand let it sit for a few hours. Then go outside, shake the second can of soda, andopen it. Make sure that you point the opening of the can away from you when youopen it. What happens? Now taste the soda thats been sitting out and the sodayou just opened. Can you feel the difference in the fizziness?

Soda has dissolved gas in it, just like lava. When the gas has lots of time to escapethe soda goes flat. The same thing happens to lava that loses its gas as it rises

to the surface. It goes flat and just pours out onto the surface without much fizz.But if theres plenty of gas still trapped in your soda, or in the lava, then look out!

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Mt. Rainier is considered one of themost dangerous volcanoes in the world.Mt. Rainier is a Decade Volcano, which

means that its one of the 16 volcanoesaround the world that could cause thegreatest destruction and loss of life. Tename Decade Volcano comes from the

program to identify these destructive volcanoes, which was part of theInternational Decade for Natural Disaster Reduction.

Mt. Rainier is so dangerous because it is an explosive volcano andit has huge amounts of glacial ice. Te hot steam and lava would melt

the ice and mix with it to form lahars. Tese mudflows can travel up to40 miles per hour (64 kilometers) and wipe out anything in their path.In the distant past, Mt. Rainiers mudflows reached as far away asSeattle, but few people lived there then. Now, there are largepopulations of people who live in the path of these mudflows. Eventhough Mt. Rainier last erupted about 150 years ago, its still an activevolcano and could erupt again. Geologists monitor volcanoes like Mt.Rainier so they can warn people before they erupt.

Words to KnoW

caldera: a bowl-like

depression at the top of avolcano. It forms when themagma chamber underneathis emptied and collapses.

Lava Tubes!When rivers of molten lava run underground, they make channels, or caves. Theseare called lava tubes. You can see lots of lava tubes in Lava Beds National Monumentin northeastern California. There are more than 700 lava tube caves, many withladders and trails. The longest lava tube in the continental United States is Ape Cavein Mount St. Helens National Monument. Its almost 2 miles long (4 kilometers)!

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Crater Lake isnt a volcano, but it sitson top of one. Mt. Mazama is a stratovolcanolocated in Oregons Cascade Range. It wasthe site of an enormous eruption 7,700years ago. Tis eruption was even bigger

than the 1980 eruption of Mount St.Helens, expelling as much as 50 to 100 timesmore material. Mt. Mazama erupted manytimes after that, and eventually the chamberthat held the magma underneath collapsed. Acaldera, or bowl-like depression, formed at thetop of the volcano. Te caldera later filled withrainwater and snowmelt to form Crater Lake.

If you think a lake at the top of a mountain must be small, thinkagain. Crater Lake is 5 miles across (8 kilometers) and up to 1,949 feetdeep (594 meters). It is the ninth-deepest lake in the world, and thedeepest lake that is entirely within the United States.

One way to tell ifa volcano is active or

not is by its shape. Older,inactive volcanoes are more

jagged, because glaciers have hplenty of time to erode the mount

Active volcanoes, which haveerupted and formed morerecently, tend to have a

smoother look.

Did

You

Know?

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Newberry Volcano is one of the most famous shield volcanoes in thePacific Northwest. all, explosive volcanoes like Mount St. Helens onlyaccount for about 25 percent of the lava that has flowed in the Pacific

Northwest from volcanoes (not including eruptionscalled flood basalts that you will learn about in

chapter 4). Most of the lava has come fromshield volcanoes. Tese quietly eject a runnylava that can spread far and wide.

Newberry Volcano is the biggest volcanoin Oregon, if youre measuring the amount oflava spewed. It is also one of the largest shield

volcanoes in the continental United States: 40miles long (64 kilometers) and 20 miles wide (32

kilometers), with a crater 4 miles wide (6 kilometers)!

Newberry Volcano last erupted 1,300 years ago. Tis eruption isknown as the Big Obsidian Flow. If you took the volume of rock in thisflow and made a paved road with it 6 inches thick (15 centimeters) and24 feet wide (7 meters), it would circle the earth three times! Geologists

think there is a chamber of magma about 2 or 3 miles beneath the surface(3 to 5 kilometers), and it could erupt again. Scientists are exploringhow the heat from this magma, known as geothermal energy, can beused to generate electricity.

Mt. Novarupta and Mt. Katmaiare two stratovolcanoes where thelargest volcanic eruption of the centuryhappened in Alaska in 1912. Tey

released 30 times the volume of magmaas Mount St. Helens eruption. Ashspread all over the world and causedroofs to collapse in Alaska.

Newberry Volcanohas lots of obsidian

in its center. This volcanicglass is used to make surgicalinstruments sharper than steel.

Obsidian was traded by

Native Americansthroughout the Pacific

Northwest.

Did You Know

?

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A valley near the volcanoes receivedhundreds of feet of ash. Tis ash was white-hot, up to 2,000 degrees Fahrenheit (1,093

degrees Celsius). Te valleys river turnedinto steam, which escaped through cracks,causing thousands of smokes. Tis areabecame known as the Valley of en TousandSmokes. It covers 40 square miles (104 squarekilometers) and is filled with ash up to 700feet deep (213 meters). Te Valley of enTousand Smokes is now part of the Katmai

National Park and Preserve.

Earthquakes!

When stress builds up in rocks, they can suddenly lurch into a newposition. Tat lurching is called an earthquake. Most earthquakes happenalong faults, which are cracks in the lithosphere, and especially at plateboundaries. You might expect there to be earthquakes in the PacificNorthwest because of the plate boundaries

located there. You would be right.In the Pacific Northwest, there are

four types of earthquakes. All ofthem are related to the oceanicJuan de Fuca Plate pushingunderneath the continental NorthAmerican Plate. Earthquakes canoccur within the Juan de Fuca

Plate, within the North AmericanPlate, between the two plates, or byrising magma as it cracks the colderrock above.

Earthquakes aremeasured mainly by their

magnitude. Magnitude is thestrength of the earthquake and

is recorded on the Richter scale. TheRichter scaleis a logarithmic scaleThis means that when the measuremenincreases by 1, the magnitude increase

by 10. So an earthquake thatmeasures 8.0 is 10 times aspowerful as an earthquake

that measures 7.0.

Did

You

Know?

Words to KnoW

obsidian:dark volcanic

glass formed when lavacools so fast it cant formcrystals.

fault:a crack in the outerlayer of the earth where therocks have moved past oneanother.

Richter scale:the scalefor measuring the strengthof an earthquake.

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Magnitude on theRichter Scale

What itFeels Like

How Often TheyOccur in the World

Below 3.0

3.0 to 3.9

4.0 to 4.9

5.0 to 6.9

7.0 to 7.9

8.0 to 8.9

9.0 to 9.9

10.0 and up

People usually cant feel it.

People can feel a slighttrembling, but there is nodamage.

Tables and chairsrattle.

Some damage to buildings,especially if theyre poorly

built.

Serious damage to buildings,with some destroyed.

Serious damage for severalhundred miles.

Devastating, affecting peoplefor thousands of miles.

Never recorded.

1,000 per day

Over 100 per day

About 20 per day

About 3 per day

18 per year

1 per year

1 per 20 years

?

Here are some typical effects that people might feel near the epicenter ofearthquakes of various magnitudes. The epicenter is the point on the earthssurface that is directly above the location of an earthquake.

What Does an Earthquake Feel like?

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Earthquakes can occur as deep as 30 miles beneath the surface of theearth (48 kilometers), or they can happen much nearer to the surface.Te biggest earthquakes occur where the two plates have been locked

together for hundreds of years, then finally release in an extra-large snap.Nearly 17,000 earthquakes of magnitude 1.0 to 6.0 have been recordedin Oregon and Washington since 1970. About 15 to 20 earthquakes peryear are felt in the Pacific Northwest.

Alaskan Earthquakes

Te 1964 Great Alaskan Earthquake occurred on March 27, 1964, inPrince William Sound near Anchorage, Alaska. It measured 9.2 on the

Richter scale. Tere was much damage to buildings and roads and 131people died. Te land moved vertically by as much as 49 feet (15 meters).It generated a huge tsunami wave 230 feet high (70 meters), one of thelargest tsunamis ever recorded.

Te Great Alaskan Earthquake is the most powerful earthquakeever recorded in North America, and the second-most powerful everrecorded in the world. Te largest was a 9.5 earthquake in Chile in 1960.

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Mima Mounds MysterySome of the most mysterious natural formations in the Pacific Northwest are calledmima mounds. These are mounds of earth up to 6 feet high and about 30 feetacross (2 meters high and 9 meters across). They are found in eastern Washington,but no one knows for sure how they got there.

But whenever theres a mystery, scientists have theories:

They were built by prairie dogs.

They arose from cracking in the soil due to drying or frost.

They grew as sediment blown by the wind clumped around vegetation.

They were formed by glaciers.

They were formed by earthquakes.

The last theory came to a man named Andrew Berg while he was building adoghouse. He was using plywood that was coated with fine volcanic ash. As hepounded away, he noticed that the ash formed into small bumps of ash, remarkablylike the mima mounds. He figured that vibrations on a much larger scale, like froman earthquake, could create the mima mounds.

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Another enormous earthquake in Alaska occurredon November 3, 2002. Te Denali earthquake inDenali National Park, measured 7.9 on the Richter

scale. Te earths surface was ruptured for 209miles (336 kilometers)! Te earthquake

created waves in Lake Union in Seattle,Washington, that damaged boats. Terewere thousands of landslides in and aroundDenali, but no one died because few people

live in the area.

Te trans-Alaskan oil pipeline, which carries

oil from the Arctic Ocean to the southern edgeof Alaska, crosses the Denali fault. Te pipelinecarries huge amounts of oil, and if it had brokenthere could have been terrible environmental

effects. But the pipeline had been designed so that it could slide onbeams during an earthquake. As a result, the pipeline wasnt damaged.

Tsunami!

When an earthquake occurs beneath an ocean,and the ocean floor moves up or down, it pushesthe water up or down quickly. Tis createsa series of giant waves called a tsunami.sunamis can also be caused by underwaterexplosions, meteorites, or landslides.

Way out at sea, tsunamis are only afoot highnot even enough for a ship tonotice. Te wavelength can be very longthough, sometimes up to 120 miles from onecrest of the wave to the next (193 kilometers).

The largest wave everrecorded in the world

occurred on July 9, 1958 inLituya Bay, Alaska. An earthquacaused a large amount of rock

plunge into the bay, generating the The tsunami wiped out trees as

as 1,720 feet above sea leve(524 meters). Thats higher

than the Empire StateBuilding!

Did

You

Know?

Words to KnoW

wavelength:thedistance from crest to crestin a series of waves.

ThinkAbout It!

Earthquakes and volcanoestend to occur in similar

locations. Why do you thinkthis is the case?

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sunamis travel as fast as a jet airplane. But when they approachthe coast, the waves slow down, bunch up, and become very high. Onewarning sign that a tsunami is coming is

that the water often dramatically recedes,or draws back, before the waves arrive.

sunamis can travel across entireoceans with devastating effects.In 1960, the earthquake in Chilegenerated a tsunami that traveledover 10,000 miles in 22 hours (16,093kilometers). When it hit Japan, 150

people were killed from the huge amountof water.

In 2004, ten-year-old Tilly Smith was with

her parents at the beach inThailand. She had learned about

tsunamis in her school geographyclass. She saw that the water waspulling back, and told her parents

that a tsunami was coming.

They warned others andsaved many lives.

Did

You

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1Set the foam coreboard outside, on

top of the bricks, withone brick on each end.Spread the flour outevenly on the board untilyou cant see the boardunderneath.

2

From underneath,gently tap the board

with the spoon over andover. Do you see the flourforming into mounds?Try tapping the boardin different places. Doesit change the mounds?Smooth the flour out andtry different thicknessesof flour. Does it affect theshape or spacing of the

mounds?

Mima Mounds

SupplieS

sheet of foam core board atleast 2 by 2 feet (by meter)

2 bricks

2 cups or more of flour orcornstarch ( liter)

large spoon

Whats Happening?Your tapping is like an

earthquake vibrating the

earth. The mima mounds

could have formed from

loose soil, like your flour,

vibrating over a hard surface

like rock underneath.

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Tsunami

SupplieS

bathtub

thin, stiff board about8 by 10 inches (20 by25 centimeters)

Whats Happening?When you quickly snap the board up, it acts like the earth under

the ocean during an earthquake. An earthquake that occurs

under the ocean causes waves that arent very high, but are

very broad. As the waves approach the land, they bunch up and

the waves become much higher. Your bathtub isnt nearly big

enough to cause such giant waves, but did you notice the waves

bunching up a bit as they came to the end of the bathtub?

1

Fill the bathtub withwater 1 or 2 inches deep

at the shallow end(2 to 5 centimeters).

2 Place the board flatunder the water atthe faucet end of thebathtub. With one hand,hold down the side ofboard away from thefaucet. With your other

hand, quickly lift theside of the boardclosest to the faucet.

3 Observe the waveyou created as it goestoward the other end of thebathtub. Does it change as itreaches the end? If you addmore water to the bathtub,does the wave change?

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Basins and Plateaus

If you had x-ray vision like Superman, you could standon the Cascade Mountains and see a vast, relativelyflat area of black rock stretching east all the way to theRocky Mountains. Some of it would be covered by soil

and some of it would be exposed to the air. But to yourx-ray eyes, it would look a bit like a black ocean.

CHAPTER 4

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Tis black rock is called basalt, and thisstretch of it is located in the ColumbiaIntermontane. An intermontane is

the area between mountain ranges.Te Columbia Intermontane covers ahuge area in the center of the PacificNorthwestover 100,000 square milesacross Washington, Oregon, Idaho, and asmall area of northern Nevada (259,000square kilometers).

Columbia

Intermontane

Te Columbia Intermontane really didused to be a kind of oceanan ocean ofhot lava flows. Tese flows werent justdribbles of lava. Tey were HUGE flows

of lava pouring out of volcanoes over and over. Tere was so much lavathat it didnt cool very quickly and could flow for months and even

years, covering great distances. Some of the lavaflowed into the ocean, even though it washundreds of miles away from the vents.

Because of how it was formed, thebasalt in this area is called floodbasalt. Te entire area is now referredto as the Columbia River Basalts. TeColumbia Intermontane has one of the

worlds largest areas of continental floodbasalts. Tese huge floods of lava buried olderrocks, creating vast lava plains.

Words to KnoW

basalt: a black, shiny volcanicrock.

Columbia Intermontane:the relatively flat area inWashington, Oregon, and Idahobetween the Cascade and RockyMountains.

vent:an opening in the earthscrust where molten lava andvolcanic gases escape. Alsocalled a fissure.

flood basalt: a giant flow ora series of very large flows of lavathat form basalt rocks.

fine-grained:rock that hasmineral grains that are too smallto see.

The ColumbiaIntermontane is

sometimes called theColumbia Plateau. Comparedto the large mountains to the

east and west of it, the ColumbiaPlateau is relatively flat. But

it still has ridges andvalleys, hills and

terraces.

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You

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Basins and Plateaus

BasaltBasalt is an igneous rock that forms when certain types of lava flows onto thesurface of the earth. Its dark gray to black and very fine-grained. Basalt is quitedense, or heavy, because its minerals are dense. It is the most common type of rockon earth, but most basalt is located on the oceans floors. The Columbia Plateau hasone of the largest areas of basalt on a continent.

When basalt lava erupts and cools, it shrinks and cracks. Often, the cracks are

very regular and the basalt forms into vertical columns that have5, 6, or 7 sides.

Sometimes basalt lava flows from a centralvent or opening, and forms aconewhat we call a volcano.But basalt lava can also flowquietly out from long openingsin the earth, called fissuresor vents. This lava is not veryviscous, which means that it

flows easily. The flood basaltsflowed out of long vents.

Te first flooding filled in valleys, thenlater floods deposited thinner, flat sheetsof basalts. Tere are many wonderful

places to view the basalt of theColumbia Intermontane. One of themis Multnomah Falls, a waterfall on theOregon side of the Columbia River Gorge.You can see five different flows of basalt onthe cliff face of the waterfall.

Alaska also hasan intermontane

plateau located betweenthe Brooks Range and theAlaska Range. Its called theCentral Plateau and its thelargest geographic region in

Alaska. Its even largerthan the state of

Texas!

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The Columbia River Basalts

Tere are many interesting facts about the Columbia River Basalts.

Te lava that formed the basalts flowed out of fissures 15 to 30 feetwide (5 to 10 meters). Tere were perhaps as many as 20,000 fissures,some as long as 150 miles (240 kilometers). Te lava flowed out as fastas 3 miles per hour (5 kilometers), faster than most animals can run forlong periods.

A total of about 63,000 square miles (163,799 square kilometers)were covered by flood basalts. Tats an arealarger than most states in the United States.

Te basalt rock has a volume of about41,820 cubic miles (179,000 cubic kilometers)and perhaps even more. If you cut the basaltinto 1-foot cubes and stacked those cubes fromthe earth to the sun, you would have 12,816towers!

In some places, the basalt is more than a

mile thick (1 kilometers).

Words to KnoW

livestock: animals raisedfor food or other products.

plume of magma: alarge area of magma that risesto the surface from deep in themantle. It has an upside-downteardrop shape.

delaminate:when thelower part splits off.

The Largest Lava FlowsIn 1783 there was an eruption from a fissure in Iceland that lasted eight months and produced3 cubic miles of lava (12 cubic kilometers). It was the largest lava flow in recorded history. Italso produced poisonous clouds that killed more than half of the countrys livestock. Over10,000 people died in Iceland, mostly from starvation, and there was famine around the

world. But as huge as the Iceland eruption was, the eruptions that spewed out the ColumbiaRiver Basalts were much greater. The Columbia basalt flows were over 100 times greater involume, and they happened over and over!

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Basins and Plateaus

Te Columbia River Basalts are the youngest flood basalts on earth.Tis means they have experienced less erosion than other flood basalts.As a result, these basalts have been studied more than any other flood

basalts in the world. Te lava erupted between 17 million and 6 million years ago. Most

of the eruptions occurred in the first 1 million years of that period.

What Causes Flood Basalts?

Flood basalts are unusual. Tey only occur aboutonce every 50 million years or so, and they dontusually happen near plate boundaries. Geologists

have different theories for how and why floodbasalts are produced, and over such a large area.

Te Plume Teorythe Big Balloonproposes that a giant, abnormally hot plumeof magmarises from deep in the earth. It meltsrock as it rises. Tese plumes are so big that whenthey break through the crust, spilling lava, they can be 500 miles across(800 kilometers).

Te Delamination Teorythe Super Sandwichproposesthat flood basalts occur when the lithosphere delaminates, and sinksdown into the mantle. Tink of the lithosphere as a sandwich. If youpeel away the bottom piece of bread, or lithosphere, it allows lots of thehotter, gooier asthenosphere below to push up and melt the rock above.It pours out as flood basalts.

Te Plume and Delamination TeoryBig Balloon Meets

Super Sandwichcombines the two. A plume of magma rises fromthe mantle and melts the lower lithosphere to start the flood basalts.While the plume moves up, the lower lithosphere begins delaminating,producing even more basalt eruptions.

Think

About It!

Which theory do youthink makes the most

sense?

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Mega flood!

Around 16,000 years ago, near the end ofthe last Ice Age, the area between Idahoand the Cascade Mountains experiencedthe largest known flood of freshwater.Te floods gouged huge channels fromthe earth, and left the basalt rocks broken,jagged, and jumbled. Tis area is now

called the Channeled Scablands, because it is like a scab on the earth.What happened to cause such massive flooding?

Glacial Lake Missoula was a massive lake in western Montana formedby a glacier that dammed the Clark Fork River. Te lake was about 2,000feet deep (610 meters) and more than 200 miles long (322 kilometers).It held more water than Lake Erie and Lake Ontario combined. Whenenough water had built up behind the ice dam, the pressure from thewater broke through the ice all at once, causing the flooding.

Te floods that followed were unlike anything seen in modern history.If you took the flow of all the rivers in the world right now, the amount

of water per hour shooting out from Glacial Lake Missoula would be 10times as much as all of them combined.

Flood water raced across the landscape at 65 miles per hour (105kilometers). It swept away hundreds of feet of soil and cut

deep canyons in the earth.Te lake was drained inabout two days. Amazingly,the glacier continued toform again and again. Atleast 13 and perhaps 70floods occurred.

Words to KnoW

Ice Age:a period of time

when glaciers covered a largepart of the earths surface.

scablands:an area withdeep, dry channels and rough,gouged rocks.

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Basins and Plateaus

Snake River Plain

Te Snake River Plain is a flat, 400-mile-long depression containingbasalt rocks. It stretches across southern Idaho and covers about aquarter of the state. Te Snake River Plain is home to most of Idahosmajor cities and agricultural land.

Many geologists think that the Snake River Plain was formed fromthe same plume of magma that caused the Columbia River Basalts.Tat plume has moved and is now under YellowstoneNational Park at the very eastern end of the SnakeRiver Plain.

Te Snake River Plain contains manyfascinating geological features, includingthe Great Rift Zone. Tis large area offractures, or breaks in the earths crust, isabout 50 miles long (80 kilometers). Its thelargest rift zone in the United States. Here,the crust is literally pulling apart, or rifting.

The lava owing in this area is sonew that theres very little vegetation.

One of the main features of the Great Rift Zone is the Kings BowlRift. Its main fissure is about 6 to 8 feet wide (2 to 2 meters) andin some areas you can actually descend into the rift several hundredfeet. Te deepest rift crack in the world is located here and its 800 feetdeep (244 meters)! Te Great Rift Zone also contains Craters of theMoon National Monument and Preserve. It has spectacular and strange

volcanoes, ropy basalt, and lava tubes. President Calvin Coolidge, whodeclared it a National Monument in 1924, called it a weird and sceniclandscape peculiar to itself.

The NationalPark Service has

proposed an Ice AgeFloods National GeologicTrail. To read more, go to

www.iafi.org/trail.html. Thistrail system would bring the

dramatic story of the IceAge Floods to the

public.

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Basins and Plateaus

By the 1950s, Bretzs ideas were finallyaccepted by other geologists. In 1979,

at the age of 96, Bretz received thePenrose Medal, the highest award ingeology.

In science, as in much else, there isno substitute for seeing somethingwith your own eyes, and coming toyour own conclusions. Thats whatJ Harlen Bretz did. And he changedthe way we think about a huge areain the Pacific Northwest, and even

geology itself.

Basins and Plateaus

ThinkAbout It!

Do you know of any other instanceswhere everyone thought they

KNEW the truth, but were actuallymistaken? What does it take to

discover the truth?

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Magma and Basalt ColumnsScientists use cornstarch and water to study how basalt forms into columns. You can

try the same thing. The only difference between what you do and what scientists dois that they have powerful microscopes to examine what is happening.

1 Ask your parents if you canuse a bright light for aboutone week. Or you can use asunny windowsill where yourproject wont be disturbed.

2

Put newspaper on the floor,

or start the project outside.Put the cornstarch in the piepan. Slowly add water, mixingwith your fingers or a spoonuntil all the cornstarch is wet.Mix enough so the pan is abouthalf full. Add food coloring ifyou like.

3 Your mixture is calledoobleck. Its fun to playwithtry slapping it hard, thenslowly sinking your fingers intoit. Make a ball of the oobleck,pressing your hands firmlytogether so that the ball feelshard. Then open your hands.What happens? You can adjustyour oobleck by adding a littlemore cornstarch if it feels toowet, or more water if it feels too

powdery.

SupplieS

bright light (100 wattsor brighter) or sunnywindowsill

newspaper

1 cup cornstarch ( liter)

pie pan, ideally clear glass

1 cup warm tap water( liter)

spoon (optional)

food coloring (optional)

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4 When youre doneplaying with the oobleck,place it back in the pan andwash your hands. Set the

pie pan at least severalinches under a brightlight, or on a sunnywindowsill. Wait atleast one week, oruntil it is completelydry. You will begin tosee cracks that breakthe cornstarch intodisconnected shapes.

Keep the cornstarchunder the light untilyou see much finercracks at the top.The longer youwait, the better.

5 If your pie pan is clear,hold it up and look atthe bottom. Do you seeany shapes? Carefully pry

up pieces ofcornstarch. Didthe cornstarch

form columns?Do they havea particularshape? Ifyou dont seecolumns, waitlonger for the

cornstarch todry out more.If youd like totry the wholeprocess again,

just add water!

Whats Happening?

When you roll oobleck around, you put a lot of pressure on themixture and it acts like a solid. But when you open your hand,

the pressure is gone and oobleck acts like a liquid. This is what

happens to a plume of magma. When its deep in the earth, it is

under a LOT of pressure and it acts like a solid, moving upward

maybe a few inches a year. But as it gets close to the surface of

the earth, the pressure is much less, and the magma partially

melts. When oobleck dries out, it acts like lava when it cools.

Most liquids (except water) shrink when they cool and becomesolid. Lava does too. Have you ever seen mud when it dries?

Does it have cracks?

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Whats Happening?Oil is less dense than water, so it weighs less. That means it floats.

But salt is denser than either oil or water, so it sinks. When you

shake salt onto the oil, at first it carries the oil with it. But soon

the salt dissolves in the water. Without the salt to weigh it down,

the oil rises againuntil you shake more salt on it!

Hot materials, like magma, are also less dense than rock. They are

like the oil in this experiment. Plumes of magma rise because theyare hotter, and weigh less, than the surrounding rock.

Magma Plumes

What makes plumes of magma rise?

Try this experiment to find out.

1 Pour the water into thejar until it is a little morethan half full.

2 Pour the oil into the jarand let the water andoil separate and settle. Youcan add food coloring if you

like.

3 Shake the salt onto theoil for several seconds, oruntil some of the oil beginsto sink. When the oil beginsto rise again, you can shakesalt onto it again. Keepgoing as long as you like!

SupplieS

clear glass or plastic jar tap water, about 1 cup ( liter)

cooking oil, about cup (8 liter)

food coloring (optional)

salt in a shaker

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he weather in the Pacific Northwest can be calmand mild. It is often the most gentle weather in theUnited States. But in the blink of an eye it can changedramatically to severe blizzards and winds that can tearthe roofs off houses. Not only that, the weather can betotally different just a few miles away. Te more you

look at the weather in the Pacific Northwest, the moreit changes!

Climate

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What makes the weather?

Te sun is the energy source that powers nearly everything in our world.Without the sun, the earth would not have light, heat, food, or life.Pretty bleak. It also wouldnt have weather.

Te suns energy heats our world and affectsthe temperature of an area. It also keeps theatmosphere in constant motion by heatingup some parts more than others. Tis createswind and affects clouds and precipitation.

Te biggest factor in how much energy

the earth receives from the sun is the angleat which the suns rays hit the ground. Whenthe sun is high in the sky, then the rays hitdirectly. But when the sun is low in the sky,

the rays hit at an angle. Te same energy is spread out over a larger area.Tats why you feel more heat from the sun at noon, when it is overhead,than just before the sun sets.

Places that are near the equator are at a lowlatitude

. Tese areas getvery direct sunlight and are hot. But as you go farther north or southfrom the equator, to higher latitudes, the sun gives off less energy. Tis isbecause its rays hit at more of an angle, so its colder.

Words to KnoW

precipitation: rain, snow,or any other form of water thatfalls to Earth.

latitude:the angle of alocation from the equator. The

latitude is 0 degrees at theequator and 90 degrees at theNorth and South Poles.

Weather and Climate: Whats the Difference?People often get weather and climate confused. Weather is what happens in theatmosphere related to temperature, precipitation, wind, and clouds. Climate isthe average weather of a place over a long period of time.


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Climate

Factors That Affect Climate

Tere are four major factors that determine an areas climate. Te latitudeof the Pacific Northwest is about halfway between the equator and theNorth Pole. Tis is called a temperate zone. Te weather varies quitea bit from season to season in a temperate zone, but is generally nottoo hot or too cold. Alaska is much farther from the equator, and so itsclimate is much colder.

Nearness to oceans is another factor affecting weather and climate.Te temperature of the Pacific Ocean doesnt change too much with theseasons. Tis is because water, especially a large body of water like the

ocean, heats up and cools down much more slowly than air or land. So ifyou live near the ocean youll probably experience temperatures that are

less extreme than land farther inland.

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Te higher you go, the colder itbecomes. Tis is because the atmosphereacts like a blanket to keep heat in. At

higher elevations, there arent as ma

geology of the pacific northwest (gnv64)

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