Published by Orpheus Books Ltd., 6 Church Green, Witney,Oxfordshire OX28 4AW England

Copyright © 2008 Orpheus Books Ltd.

All rights reserved. No part of this book may be reproduced or utilized in anyform or by any means, electronic or mechanical, including photocopying,recording or by any information storage and retrieval system, without permissionin writing from the publisher except by a reviewer who may quote brief passagesin a review.

A CIP catalogue record for this book is available from the British Library

Created and produced by Nicholas Harris,Sarah Hartley and Erica Simms, Orpheus Books Ltd.

Text by Nicholas Harris

Illustrated by Gary Hincks, with other illustrations byJulian Baker, Steve Noon and Claudia Saraceni

Printed and bound in Malaysia

ISBN xxxxxxxxx

P A N O R A M A S

Orpheus

Oil comes fromthe remains oftiny prehistoriccreatures thatlived in theoceans millions ofyears ago. Theremains sank to the

sea bed where theywere buried underlayers of sand and silt.These layers graduallyturned into sedimentary

rock. Bacteria changed the creatures’ remains into oiland gas. As movements in the Earth’s crust folded andcracked the layers of rock above, oil forced its way up,finally becoming trapped under a layer of hard rock.When oil is found, a drill from a well built on the seabed sends it gushing to the surface (above).

Waterfalls (left) formwhen a river cascadesdown a cliff, or where itsbed changes from hardto soft rock. The riverwears away the softerrock more quickly, so a“lip” of hard rock formson the river bed.

When rainwater trickles intocracks in limestone, itdissolves the rock, eventuallyhollowing out caves (right).As water drips from a caveceiling, the limestonedissolved in it hardens toform icicle-like stalactites.Stalagmites grow up fromthe floor where the drips fall.

There are three kinds of rock. Igneousrocks, such as granite, are formed whenmagma cools and solidifies. Sedimentaryrocks, such as sandstone and limestone,are made from fragments of rock or livingthings. Metamorphic rocks, such asmarble (right), are formed when any kindof rock is changed by great heat orpressure underground. EARTH

Fossils are the remains of once-living things preserved in rock.The soft parts rot away, but hardbody parts, such as bone, teethand shell (as in this ammonite,right) may remain.

4 Inside the Earth

6 Volcanoes

7 Moving Plates

12 Earthquakes

14 Water Cycle

15 Landscapes

20 Future Earth

22 Glossary and Index

CONTENTS

THE EARTH IN SPACEThe Earth is one of eight major planets that goaround the Sun, our nearest star. It speeds alongat about 30 km per second, taking 365.26 daysto complete one orbit. As it goes, it spins like atop once every 24 hours. It is itself orbited bythe Moon, which takes 27.3 days to go round.

54

MANTLE

CONVECTIONCURRENT

CRUST

CRUST

CORE

OUTERCORE

INNERCORE

THE MANTLEThe upper mantle is made ofpartly melted rock—crystals ofsolid rock with molten or liquidrock in between. Called magma,its temperature is about2000˚C. It flows like hot tar on anewly surfaced road.Sometimes, magma bursts outof holes or cracks in the crustas the red-hot lava in volcaniceruptions (see page 6).Below the upper mantle, the

enormous weight of the layersabove ensures that the lowermantle rocks are solid—but notcompletely rigid: they can move.Inside the mantle, the rock

actually flows, very slowly ingiant circles called convectioncurrents (above). These currentscause the tectonic plates at thesurface (see page 8) to moveabout, colliding into, pullingapart from, or sliding past oneanother.

THE COREThe core is made of iron, with small amounts of nickel. In the outer core,the temperature rises to more than 3000˚C, hot enough for the metal tobe liquid. It flows in giant, swirling currents as the Earth spins round. Nearer

the centre of the Earth the pressure from theweight of the layers above is millions of

times greater than at thesurface. This is enough to

turn the liquid ironsolid, even attemperaturesof up to

THE SURFACE of the Earth, its crust, is hardand rocky. But the crust is really just a thin

shell: you would not have to travel downtoo far down inside the Earth beforethe rocks become so hot theyare partially melted. Thislayer of the Earth iscalled the mantle. Thedeeper you go, thehotter it gets.Eventually, youreach the core,which is notmade of rockat all, butmetal.

INSIDE THE EARTH

MANTLE

2900 km

5150 km

6400 km

10-30 km

THE EARTH’S outer layer, the crustcoupled together with the top of the

upper mantle, is divided into enormouspieces, called tectonic plates. Theplates are continually on the move,driven by currrents in the mantle below(see page 5). As they move, their edgesrub and grind against each other.Over hundreds of millions of years,

moving plates have resulted in entirecontinents wandering about the globe,sometimes joining together, sometimesdrifting apart.

MOVING PLATES VOLCANOESMany volcanoes are found closeto subduction zones (see below).Forced down to great depths, therocks eventually melt. Somemagma finds its way to theEarth’s surface through cracks inthe rocks above. There it erupts aslava. Volcanoes rising from theocean floor may eventually growlarge enough to form islands.

OCEAN TRENCHSome plates are made mostly of oceanfloor, while others consist mainly of landmass or continent. At the boundarybetween an oceanic plate and a continentalplate, the denser oceanic plate slides downbeneath the continental one. This is knownas subduction. At the surface, a deepocean trench is formed.

OCEAN FLOORThe ocean floor is made fromlava that has erupted, rapidlycooled under the water andsolidified. As more and morelava erupts, cools andsolidifies, a new ocean floor isgradually formed

RIFT VALLEYWhere two plate edges pull away from one another onland, a block of land slips down between them. Thiscreates a large, wide valley, called a rift valley. The GreatRift Valley in East Africa was formed in this way.

In some places along the mid-oceanic ridge, hot waterjets up through tall “chimneys”, called black smokers.Although there is no sunlight at these depths, strangeanimals are able to exist down here, including redworms that live in white tube shells. They live off thebacteria that thrives on the nutrients in the hot water.

PUSH, PULL OR SLIDESome plates are moving apart, others arepushing together. In some places, oneplate slides down below another. Inothers, two plates slide past each other,moving in opposite directions. When twoplates push together, the land slowlycrumples up, forming mountains.

MID-OCEANIC RIDGESnaking its way across thefloor of all the world’s oceansis the mid-oceanic ridge. Thismarks the boundary betweenplates. Here the plates arepulling away from one another.As they do so, magma rises up

FAULTSA fault is a crack in theEarth’s crust, either side ofwhich rocks may shift indifferent directions. Someplate boundaries are majorfaults. One famousexample is the SanAndreas Fault in California,USA. Here, the NorthAmerican plate and thePacific plate are slidingpast one another inopposite directions. Thearea close to the SanAndreas Fault is vulnerableto earthquakes (see pages12-13). These occur whenthe two plates locktogether for a time.Eventually the pressurebecomes too great and therocks suddenly snap apart.

between them fromthe mantle below. Theerupted lava spreads out toeither side forming a new oceanfloor. The plates move apart byup to several centimetres ayear—similar to the rate atwhich fingernails grow.

AA JJ II GG SS AA WW PP UU ZZ ZZ LL EE

BB LL AA CC KK SS MM OO KK EE RR SS

THE EARTH’s surface is like a jigsaw puzzlewrapped around a giant ball. It is divided intojagged-edge pieces, called tectonic plates.There are eight largeplates and 12-15smaller ones.They slideabout on asurface ofpartly moltenrock in theupper mantle.

TWO PLATE EDGESPULL AWAY FROMEACH OTHER

TWO PLATE EDGESPULL AWAY FROMEACH OTHER

TWO PLATEEDGES SLIDEPAST EACHOTHER

VOLCANO

ONE PLATEEDGE SLIDESDOWN BENEATHANOTHER

UPPER MANTLE

CRUST

MOUNTAINS

RIFT VALLEY

OCEANFLOOR

OCEANTRENCH

7 8 9 10

MID-OCEANIC RIDGEFAULT

MAGMA RISESFROM BELOWTHE CRUST

MAGMA

OCEANFLOOR

SOLIDIFIEDLAVA

CONVECTIONCURRENT

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AN EARTHQUAKE is a shaking of the groundcaused by the sudden movement of rocks in

the Earth’s crust. Thousands of earthquakeshappen around the world each year, butare too small to be noticed, or affectonly remote areas. Butoccasionally a massiveearthquake may collapsebuildings andbridges in cities,causing

EARTHQUAKES12 13

SHOCK WAVESThe precise point where therocks slip is called the focus.The epicentre is the point onthe Earth’s surface directlyabove the focus. Judderingshock waves travel out in alldirections from the focus. Fromthe epicentre, they spread outlike ripples on a pond.

A SUDDEN SLIPMany earthquakes occur alongsubduction zones, those placeswhere one tectonic plate edge issliding beneath another (see page 8).When these sliding plates locktogether for a while, the pressurebuilds up in the rocks underground.Eventually the pressure is too much:the rock suddenly slips, causing amajor earthquake. Places most atrisk are the shores of the PacificOcean, and the region extendingfrom Northern India to Europe.

VOLCANO

OCEANTRENCH

RISINGMAGMA

PLATEMOVEMENT

PLATEMOVEMENT

SHOCKWAVE

EPICENTRE

FOCUS

TSUNAMIWhen a powerful earthquake occurs under the sea bed, thesudden movement triggers a massive wave, called a

tsunami. This travels out from the epicentre in alldirections. In the open sea it is barely

noticeable, although it travels at highspeed. On reaching shallow coastal

waters, the tsunami rears upinto a colossal wave up to

30 m high. A wall ofwater surges

ashore with

The Chinese invented this clever earthquake detector inthe second century AD. Each of eight dragons fixedaround a bowl holds a ball in its jaws. If the device isshaken by an earthquake tremor, a rod inside the bowl

swings and opens oneof the dragon’s jaws.This drops a ball intothe toad’s mouth belowwith a loud clang. Inthis way, the direction ofthe quake is recorded.Modern earthquakedetectors are known asseismographs.

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WAVES TRAVELOUT IN ALLDIRECTIONS

WAVE HEIGHTINCREASES IN

SHALLOW WATER

TSUNAMISURGESASHORE

OCEAN FLOOR

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OVER MILLIONS of years, vastmountain ranges are pushed up

by the movement of tectonic plates(see page 7). Millions of years later,they may have disappeared, worndown by the slow processes ofweathering and erosion. Extremetemperature change and the freezingof water collected in cracks gnawaway at the rocks. The action ofrunning water, glaciers and windcarries away rock fragments.

LANDSCAPES

COASTLINESSome coastlines are shaped bythe action of the waves crashingashore. Over time, they wearaway the rocks. Cliffs are shapedby rockfalls and landslides aswell as by waves. Sometimeswaves may carve a hole rightthrough a rocky headland to form

an arch. If the roof of the archlater collapses, a tall, thin islandcalled a stack, is left standing.As rocks break down intofragments, sea currents pile upthe resulting sand or shingle onthe shore to form beaches. Widebeaches may protect cliffs fromfurther battering by the sea.

UPPER WATERSA river may start out as a springgushing from the ground, asmeltwater from a glacier, orwhen rainwater collects on the

LOWLAND RIVERSLower in its course, the river’s slope is gentlerand its waters flow more slowly. It widens asother smaller rivers, called tributaries, join it.The river starts to shed its load of mud andshingle. Over flatter ground, it flows in hugecurves called meanders.

ground. Its upper waters flowswiftly and steeply. They carvedeep valleys in the rocks byerosion, and carry away mudand shingle downstream.

SPITS AND BARSStrong sea currents may scouraway sand or shingle from onepart of the shore and dropthem further along where thecurrents are slower. Wheresand or shingle is laid downacross an estuary or bay, a spit

GLACIERSA glacier is a mass of ice that movesslowly downhill. Snow piles up at thehead of a high valley until it turns toice. Thick and heavy, it may start tomove under its own weight. As the icegrinds its way down a valley, it gougesout loose rocks. These collect in theice as bands called moraines. Furtherdown the valley, where the ice melts,the rocks are dumped in piles calledend moraines.

DESERTSApproximately one eighth of theEarth’s land surface is desert:arid land with very low rainfall.Some deserts, such as theSahara, are hot all year round,

while others, such as the Gobi,are hot in summer and cold inwinter. Only about one fifth ofthe world’s hot deserts aresandy. Most are vast areas ofgravel or bare rock.

following rainstorms erode awaysteep-sided valleys called wadis.In some deserts, hard rock

resists erosion. Flat-toppedmountains called mesas andchimney-like buttes are the result.

Desert winds blowing in thesame direction may pile upcrescent-shaped dunes calledbarchans. Windblown sand maycarve amazing shapes in therocks. Fast-flowing floods

may form. The spit mayeventually become a bar, withboth ends attached to land.Coastal marshes may start togrow in lagoons, the shelteredwaters behind spits or bars.

DD EE LL TT AA

Where a river meets the sea it may sometimesdivide into many smaller channels, interspersedwith islands of mud and shingle. This is calleda delta, after the Greek letter in the shape of atriangle. Deltas can push out to sea in to formdifferent shapes, as well as triangular ones.

MELTWATERLAKE

15 16 17 18

GLACIER

MORAINE

BAYARCH

CLIFFSSTACK

GLACIER

LAKE

ESTUARY

BEACH

LAGOON

RIVER

RIVER

TRIBUTARY RIVER

LAKE

MESA

COASTAL MARSHES

RIVERMEANDERS

DELTA

SPIT

SALT LAKE

DESERT BARCHANDUNES

BUTTES

MOUNTAINS

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WHAT WILL the future hold for ourplanet? Already, people are very

concerned about the damage being doneto our environment. Emissions from ourfactories, vehicles, planes and powerstations pollute the air and sea—and addgreenhouse gases to the atmosphere.Clearing forests removes the naturalhabitats of many animals. Some speciesare already threatened with extinction.

FUTURE EARTH 2120

NORTHAMERICA

SOUTHAMERICA

ATMOSPHERE

EARTH’S SURFACE

GREENHOUSEGASES IN

ATMOSPHERETRAP HEAT

SUN’SRAYS

HEAT REFLECTEDBACK INTO SPACE

EUROPE

AFRICA

ASIA

AUSTRALIA

ANTARCTICA

THE GREENHOUSE EFFECT The Sun’s rays warm the surface of the Earth. Thesurface then reflects this heat back into space. Somegases in the atmosphere, such as carbon dioxide andmethane, trap part of this outgoing heat, keeping thesurface warm—just like a greenhouse. But too muchof these greenhouse gases from burning fossil fuelslike coal and oil will warm up the Earth too much ...

GG LL OO BB AA LL WW AA RR MM II NN GG

The Earth is becoming warmer. The averagetemperature is predicted to rise by 2˚C by 2050,although this figure is very uncertain. Theeffects may be felt by more frequent droughtsand shifting climate patterns. The ice caps atboth poles will start to melt, resulting in risingsea levels and the flooding of coastal regionswhere most of the world’s cities are located. Why is this happening? Most scientists areconvinced that human activities has resulted ina large increase of greenhouse gases, causingthe Earth to warm up (see opposite).

A MAP OF THE FUTUREThis (left) is how a map the world mightlook 50 million years from now. As thetectonic plates have shifted about (seepage 7), whole continents and oceanshave gradually changed shape. Northand South America have separated, EastAfrica has started to split apart from therest of Africa, while Australia has movednorth to collide with Indonesia.

ASTEROID COLLISIONBillions of rocks, known as asteroids, orbit the Sun. Manyare tiny—only a few metres across—but probably about abillion have diameters of more than 1 km. Most asteroidsorbit the Sun in a band between Mars and Jupiter, butsome follow orbits that bring them close to Earth’s orbit. What if one of these near-Earth asteroids were ever to

collide with our planet? The explosion would causeimmense devastation and fill the atmosphere with dust.This would blot out the Sun and lower temperatures foryears on end. The consequences for people would becatastrophic. No wonder astronomers are keeping a closeeye on asteroids that may get too close for comfort ...

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GLOSSARY INDEXASH, VOLCANIC Lava that has been blown topowder by the force of the explosion when avolcano erupts.

CONVECTION CURRENTS The continualmovement of a substance as it heats up andrises, cools and sinks, then heats up etc.

CORE The innermost portion of the Earth.

CRUST The thin, rocky outer layer of the Earth.

CRYSTALS A solid substance with a regulargeometric shape.

EARTHQUAKE A shaking or trembling of theground, caused by the sudden movement ofpart of the Earth’s crust.

EROSION The wearing away of the Earth’ssurface by water, ice or wind.

FAULT A crack in the Earth’s crust, alongwhich there is movement of one side relativeto the other.

FOSSIL The ancient remains of a once-livingthing, usually found preserved in rock.

GLACIER A mass of ice, produced by theaccumulation of snow, that moves downhill.

IGNEOUS ROCK A type of rock formed frommagma that has cooled and hardened.

LAVA Magma that has erupted on to the Earth’s surface through volcanoes.

MAGMA Hot, melted (molten) rock that comes from beneath the solid rock of the crust.

MANTLE The layer of the Earth that lies between the crust and the core.

METAMORPHIC ROCK A rock that haschanged due to intense pressure or heat.

MID-OCEANIC RIDGE A long mountain range under the ocean, where magma rises tothe Earth’s surface.

PLATES, TECTONIC The large slabs into whichthe Earth’s surface is divided.

SEDIMENTARY ROCK A type of rock that isformed by the pressing together of rockfragments or the remains of living things.

SUBDUCTION The process by which the edgeof one plate slides beneath another.

VOLCANO An opening in the Earth’s crustthrough which magma erupts.

WATER CYCLE The process by which watercirculates between ocean, atmosphere and land.

WEATHERING The fragmentation of rockscaused by temperature change, rain or frost.

22 23

Aaltocumulus 19altostratus 19ammonite 2arch 15, 16ash, volcanic 6, 11, 22asteroids 21collisions 21

atmosphere 14, 20, 21

Bbacteria 2, 9barchans 18bars 17bay 15, 17beach 15black smokers 9buttes 18

Ccarbon dioxide 21caves 2cirrocumulus 19cirrostratus 19cirrus 19cliffs 15, 16climate change 20clouds 14, 19, 21coal 21coastlines 16condensation 14, 19continent 8continental drift 7, 21convection currents 5, 7, 22

core 4, 5, 22crater 6, 11crust 4, 5, 6, 7, 9, 10, 22crystals 5, 14, 19, 22cumulonimbus 19cumulus 19

DEdelta 18deserts 17, 18

droughts 20Earth,future of 20, 21interior of 4, 5landscapes of 15movements in 2, 7, 8, 10, 12, 13, 15

orbit of 4, 21earthquakes 10, 12, 13, 22environment 20epicentre 13erosion 15, 17, 22estuary 16, 17evaporation 14extinction 20

Ffault 10, 22floods 18, 20focus (of earthquake) 12forest clearance 20fossils 2, 22fossil fuels 21

GIgas 6, 21glaciers 15, 16, 17, 22global warming 20Gobi 18Great Rift Valley 7greenhouse effect 21greenhouse gases 20, 21ice 14, 15, 19ice caps 20igneous rocks 2, 22iron 5islands 8

Llagoons 17, 18lake 15, 16, 17landslides 16lava 5, 6, 8, 9, 11, 22bombs 6

limestone 2

Mmagma 2, 5, 6, 8, 9, 10, 11, 13, 22

mantle 2, 4, 5, 7, 8, 9, 10, 22

marble 2marshes 17meanders 17meltwater 15, 17mesas 17, 18metals 4, 5metamorphic rocks 2, 22methane 21mid-oceanic ridge 9, 22Moon 4moraines 15mountains 6, 7, 10, 15mud 17, 18

NOPnimbostratus 19ocean floor 8, 9, 12ocean trench 8, 12oceans 2, 14oil 2, 21planets 4plates, tectonic 5, 7, 8, 9, 10, 12, 15, 21, 22

poles 20pollution 20Pompeii 11pyroclastic flow 6, 11

Rrain 14, 17rift valley 7rivers 2, 14, 17, 19rockfalls 16rocks 2, 5, 6, 8, 10, 11, 12,15, 16, 17, 18, 19, 21volcanic 6, 11

SSahara 17salt lake 18

San Andreas Fault 10sand 16, 17, 18dunes 18

sandstone 2sea 2, 13, 14, 16, 17, 18bed 2, 13currents 17rising levels of 20

sedimentary rocks 2, 22seismograph 13shingle 16, 17, 18shock waves 13snow 14, 15spits 17, 18spring 17stack 15, 16stalactites 2stalagmites 2stratocumulus 19stratus 19subduction zones 8, 12, 22Sun 4, 14, 21

TVtributary 17tsunami 13valleys 7, 15, 17, 18vent (of a volcano) 11Vesuvius, Mount 11volcanic eruptions 5volcanic plug 6volcanoes 6, 7, 8, 13, 22active 6dormant 6extinct 6, 11

Wwadis 18water 14, 15, 17, 19water cycle 14, 17, 22water vapour 14, 19waterfalls 2waves 13, 16weathering 15, 22wind 15, 18

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