1. *Earth Sci Prelims (1-7).qxd 12/12/08 11:02 AM Page 1
SCIENCE VISUAL RESOURCESEARTH SCIENCEAn Illustrated Guide to
Science The Diagram Group
2. *Earth Sci Prelims (1-7).qxd 12/12/08 11:02 AM Page 2Earth
Science: An Illustrated Guide to ScienceCopyright 2006 The Diagram
GroupAuthors: Simon Adams, David LambertEditors: Gordon Lee, Jamie
StokesDesign:Anthony Atherton, bounford.com, Christopher Branfield,
Richard Hummerstone, Lee Lawrence, Tim Noel-Johnson, Phil
RichardsonIllustration:Peter WilkinsonPicture research:Neil
McKennaIndexer: Martin HargreavesAll rights reserved. No part of
this book may be reproduced or utilized in any formor by any means,
electronic or mechanical, including photocopying, recording, orby
any information storage or retrieval systems, without permission in
writing fromthe publisher. For information contact:Chelsea HouseAn
imprint of Infobase Publishing132 West 31st StreetNew York NY
10001For Library of Congress Cataloging-in-Publication data,please
contact the publisher.ISBN 0-8160-6164-5Chelsea House books are
available at special discounts when purchased in bulkquantities for
businesses, associations, institutions, or sales promotions. Please
callour Special Sales Department in New York at 212/967-8800 or
800/322-8755.You can find Chelsea House on the World Wide Web
athttp://www.chelseahouse.comPrinted in ChinaCP Diagram 10 9 8 7 6
5 4 3 2This book is printed on acid-free paper.
3. *Earth Sci Prelims (1-7).qxd 12/12/08 11:02 AM Page
4ContentsMalestrom1 EARTH AND SPACE 8 Earths orbit18 The Moon:
structure 9 Earths shape and size 19 Solar and lunar eclipses10 Day
and night time zones 20 Structure of Earth11 The seasons21 Earths
magnetic field12 Latitude and longitude 22 Earths magnetosphere13
The solar system 23 Meteors14 Structure of the Sun 24 Meteorites15
The Suns energy 25 Elements: universal16 The Moonabundance17 The
Moon: surface2 EARTHS HISTORY26 Superposition41 Ordovician period27
Unconformities 42 Silurian period28 Complex rock sequences 43
Devonian period29 Paleomagnetic dating 44 Mississippian period30
How fossils form 45 Pennsylvanian period31 Fossil use in rock 46
Permian period correlation47 Triassic period32 Correlating rocks48
Jurassic period33 Tree of life 49 Cretaceous period34 Evolutionary
clocks50 Paleocene epoch35 Mass extinctions 51 Eocene epoch36
Geologic time52 Oligocene epoch37 Archean eon53 Miocene epoch38
Proterozoic eon54 Pliocene epoch39 Phanerozoic eon55 Pleistocene
epoch40 Cambrian period56 Holocene (recent) epoch
4. *Earth Sci Prelims (1-7).qxd 12/12/08 11:02 AM Page 53
EARTHS ROCKS57Origins83 Metamorphism58Elements 84
Progressive59Internal heat metamorphism60Periodic table 85 The rock
cycle61Atoms86 Continental drift: fit62Compounds87 Continental
drift: geology63Isotopes and ions88 Continental drift:
biology64Crystals and minerals89 Continental drift: polar65Crystal
systems paths66Rock forming minerals90 Wegeners theory67Hardness 91
Continents: 250 million68Igneous rocks years ago69Intrusive igneous
rocks92 Continents: 180 million70Magma productionyears
ago71Volcanoes: active93 Continents: 60 million72Volcanic
typesyears ago73Volcanoes: caldera 94 Lithospheric
plates74Volcanoes: lava forms95 Plate tectonics75Volcanoes: central
96 Crust and lithosphere76Volcanoes: fissure 97 Oceanic
crust77Volcanoes: shield98 Hawaiian Islands78Geysers and hot
springs99 Dating the seafloor79Sedimentary rocks:100 Spreading
ridgesformation 101 Continental crust80Sedimentary rocks:
clastic102 Continent growth81Sedimentary rocks:103 Isostasyorganic
and chemical104 Ore82Sedimentary rocks:105 Coalbedding 106 Oil and
gas
5. *Earth Sci Prelims (1-7).qxd 12/12/08 11:02 AM Page 64 AIR
AND OCEANS107Atmosphere: structure 128 Hurricanes108Atmosphere:
layers129 Tornadoes109Radio waves 130 Pressure systems110The
nitrogen cycle131 Air masses111The carbon and oxygen 132 Water
cycles133 Oceans112Heat transfer processes 134 Ocean
temperatures113Sunshine135 The ocean floor114Temperature belts 136
Seafloor profiling115Pressure belts137 Tides116The Coriolis effect
138 Ocean currents117Wind circulation139 Wave features118Jet
streams 140 Wave types119Coastal breezes 141 Bays and
headlands120The Beaufort scale of 142 Sea cliffs wind speeds 143
Waves and beaches121Humidity144 Longshore drift122Fog 145 Spits and
bars123Cloud types 146 Raised coastlines124Rain, snow, and sleet
147 Submerged coastlines125Rain types148 Coral
reefs126Thunderstorm149 Atolls and guyots127Cyclones5 SHAPING THE
SURFACE150Mechanical weathering 157 Soils of the USA151Mechanical
and organic158 Mass movement weathering159 Slopes152Chemical
weathering 160 Water cycle153Chemical weathering:161 Groundwater
hydration 162 Chalk and limestone154From granite to sand163
Rivers155Soil formation164 Rapids and waterfalls156Soil textures
165 River transport
7. *Earth Sci Prelims (1-7).qxd 12/12/08 11:02 AM Page
3IntroductionEarth Science is one of eight volumes in the Science
VisualResources set. It contains six sections, a comprehensive
glossary,a Web site guide, and an index.Earth Science is a learning
tool for students and teachers. Full-color diagrams, graphs,
charts, and maps on every page illustratethe essential elements of
the subject, while parallel text provideskey definitions and
step-by-step explanations.Earth and space provides an introduction
to the study of ourplanet in the context of the solar system.
Issues such as Earthsdependence on the Sun, and reciprocal
influence with the Moon,are illustrated and discussed, as the
elementary concerns of theearth sciences are introduced.The concept
of geologic timea timescale staggering by thestandards of human
historyis expanded in Earths history.Reference is made to the
fossil traces of past life that enablemodern paleontology to make
deductions about the developmentof life-forms, while the land of
the present-day USA is presented asa familiar point of reference in
a story of unceasing change.Earths rocks introduces the elementary
chemistry and physicsunderlying the geology of the planet, and
discusses how mineralsform rocks. The three major classifications
of igneous,metamorphic, and sedimentary rock are examined in detail
beforethe chapter returns to the origins of Earths current
surfacealignment and mineral resources.Air and oceans examines in
detail Earths unique and life-sustaining atmosphere and surface
water.Shaping the surface looks at the physical geography of the
landand how it is naturally shaped by weather and water
movement.Finally, familiar and significant geographical features of
the worldare statistically compared in Comparisons.
8. *01 Earth-space (8-25).qxd 12/12/0811:04 AM Page 8 8EARTH
AND SPACEEarths orbit Key wordsGravity and inertia
aphelionperihelion asteroidplanet comet gravitytendency orbitto
moveactual orbitEarth, speedGravity and inertia 18.2 miles per
second Theplanet Earth tries to speed(29.8 kmps)through space in a
straight line. The force ofSuns gravitational force tries to pull
gravitationEarth into the Sun. Inertiathetendency of an object to
resist a forcechanging its speed or directionprevents this from
happening. Instead,the captured Earth continually orbitsthe Sun.
Earth orbits the Sun at a meandistance of 92,960,000
miles(149,600,000 km). Sun Earths orbital velocity is 18.5 milesper
second (29.8 kmps).Earths path Earthrevolves around the Sun in
acounterclockwise direction if viewedfrom space. Each years
complete revolution tracesan elliptical orbit bringing Earthclosest
to the Sun in January andEarths pathfurthest away in July. The
point atannual circuitwhich a planet, comet, or asteroidmost
closely approaches its sun istermed perihelion, while the
pointfurthest away is aphelion. Earth At perihelion, about January
3rd,Earth comes within 91,400,000 miles(147,100,000 km) of the Sun.
At aphelion, about July 4th, it is94,510,000 miles (152,100,000
km)from the Sun. Sunperihelion aphelion (about July 4)(aboutJanuary
3) Diagram Visual Information Ltd.
9. *01 Earth-space (8-25).qxd 12/12/0811:05 AMPage 9 9Earths
shape and size EARTH AND SPACEKey wordsEarths sizeellipsoidNorth
PoleAlexandria, equatorSouth Pole AlexandriaSyene Egypt:
pillarcasts shadow geoid of 7.5 Suns raysat noon, axislongest
dayEarths sizeEarths Around200 BCEcenter Eratosthenes calculated
Earths circumference bymeasuring angles equator made by the Suns
rays at noon at two places a known distanceSyene, Egypt:Sun
verticallyapart, one south of theover wellother. Parallel sunrays
cast ashadow at midsummer noon, which atAlexandria, Egypt, was at
7.5 to theEarth: nearly an ellipsoidvertical. At the same time, in
the southperfect sphereat Syene (present-day Aswan), theSuns rays
fell vertically down a well. polar diameter Earth: nearly an
ellipsoid Thedistance from the North Pole to the South Pole of
7,900 miles (12,714 km) is 26 miles (42 km) equatorial diameter
shorter than the distance across the equator, which is 7,926 miles
(12,756 km). The shape of Earth can be represented ellipsoid as a
near-ellipsoid by visuallyThe diagram shows anellipsoid against a
perfectexaggerating the differences betweensphere. Earth is almost
an its polar and equatorial diameters.ellipsoid. The geoid: Earths
actual shapeThe geoid Thegeoid is Earths actual shape North
Polecalculated to take account of its mass, elasticity, and rate of
spin. It follows +18.9 mean sea level in the oceans and is miles
perfect ellipsoid slightly pear-shaped, with the NorthgeoidPole
18.9 miles (30 km) further from Earths center than other places and
the South Pole 25.8 miles (42 km) nearer. Diagram Visual
Information Ltd. The diagram stresses Earths pearlikeThe diagram
shows ashape by visually exaggerating smallgeoidan approximation
differences in distance from surfaceof Earths actual shapeagainst
an ellipsoid. Theto center.geoid is visuallyexaggerated to
illustrate-25.8its difference from an ideal miles South
Poleellipsoid.
10. *01 Earth-space (8-25).qxd12/12/0811:05 AMPage 10 10EARTH
AND SPACEDay and night time zones Key words Day and night longitude
meridian prime meridian Sun time zonemidnight noon Suns raysDay and
night Earthspins like a spinning top, andcompletes one revolution
every24 hours. As it spins, each place on itssurface moves into
sunlight anddaytime, and then into the Sunsshadow and night. When
North America faces away fromthe Sun it is night there. When North
America faces the Sunit is day there.Time zonesmidnight noon Suns
rays The world is divided into standardtime zones based on the
prime (orGreenwich) meridian at 0 longitude. With local
adjustments, each standardtime zone is a 15 degree band east orwest
of the prime meridian andrepresents a difference in time ofone
hour. sunriseInternational date line prime meridian World time
zones 0 3 12 Diagram Visual Information Ltd.3 12 4 12 5 12 6 12 9
12 0 +1 +2+3+4 +5+6 +7 +8 +9+10 +11 +12 11109 8 7 6 5 43 2 10
11. *01 Earth-space (8-25).qxd12/12/08 11:05 AMPage 11 11The
seasonsEARTH AND SPACEKey wordsSummer solsticeequinoxJune
21rotationsolsticeof Earth North Pole rays ofArctic Circle the
SunSun (6630 N)equator Seasons Earth Seasons are periods of the
year with rays of the Sun orbitNightcharacteristic weather. Many
tropicalDayand subtropical regions have only wet Earth orbit and
dry seasons. Temperate regions such as North America and Europe
have fourAutumnal (fall) equinoxseasons: spring, summer,
fallSeptember 23 (autumn), and winter. North Pole Seasons result
from the fact that Earths axis of rotation is not perpendicular to
the plane of its rays of Sunthe Sun orbit around the Sun, but
tilted by rays of 23.5 degrees. Earththe Sun This tilt means that
Northern andorbitSouthern hemispheres receive moreEarthor less
sunlight depending on whetherorbitthey are tilted toward or away
fromequator the Sun. Seasons depend on the intensity of solar
radiation, so the northern summer coincides with the southernWinter
solstice winter and vice versa. The diagramsDecember 22 show
seasons for the NorthernEarth orbitEarth North PoleHemisphere.
orbitrotationof EarthArctic Circlerays of Summer (6630 N)Sunthe Sun
Atthe summer solstice the NorthernHemisphere is tilted toward the
Sun.Summer is the hottest time of year.rays ofthe Sun equatorFall
(autumn) Atthe autumnal equinox, the Sun isdirectly overhead above
the equator.In the fall daytime grows shorter,crops ripen, and
deciduous treesVernal (spring) equinox shed leaves.March 21
rotation North Poleof EarthWinter Earth Atthe winter solstice, the
NorthernArctic CircleorbitHemisphere is tilted away from the
Diagram Visual Information Ltd. (6630 N) rays ofSun. Winter is the
coldest time of year. the SunDaytime hours are shortest.
Plantgrowth slows or stops.rays Sunof theSunequator Spring Atthe
vernal equinox, the Sun isoverhead at the equator. In spring
dayslengthen and plants grow.
12. *01 Earth-space (8-25).qxd12/12/08 11:05 AM Page 12 12
EARTH AND SPACE Latitude and longitude Key wordsLatitudeLongitude
Earth poleObtaining an angle of latitudeObtaining an angle of
longitude equator latitude longitudeNorth prime meridian prime
meridian Pole resulting (longitude 0)resultingparallel of
meridianlatitudeLatitude Latitudeis a position on Earths
Earthssurface north (N) or south (S) of thecenterEarths
axisequator, the imaginary line around themiddle of Earth. angle of
equator longitude Degrees of latitude are measured as (latitude
0)angles from the center of Earth. Aresultingdegree () of latitude
is divided into 60 meridianSouth measured angleprime
meridianminutes (). A minute is divided into 60 (longitude 0) Pole
of latitudeseconds ("). A line joining locations with the
samelatitude is called a parallel. Parallelsare so called because
they run parallelto the equator and to one another. The equator is
at latitude 0. TheDegrees of latitude Degrees of longitudeNorth and
South poles lie at latitudes907590 N and S.6045Longitude 30north
latitude Longitude is a position east (E) or15 (N)west (W) of the
prime meridian, animaginary line on Earths surface,0 90 60 30 030
60 90passing through Greenwich, England,south 15and joining the
North and Southlatitude30(S)poles. The prime meridian is at
longitude 0.Meridians are measured up to 180 Eor W of
it.westeastlongitude (W)longitude (E) Degrees of longitude are
measured asangles from the center of Earth anddivided into minutes
and seconds. Lines of longitude are 69 miles(111 km) apart at the
equator, butKey latitudes Key longitudebecome closer together as
their Arctic Circle66 30 Ndistance from it increases.tropic
ofCancer23 27 Nequator 0tropic of Diagram Visual Information
Ltd.Capricorn23 27 SAntarctic Circle66 30 S Greenwich (prime)
meridian 0World time is calculated from the primemeridian (0).
13. *01 Earth-space (8-25).qxd12/12/08 11:05 AM Page 13 13The
solar system EARTH AND SPACEKey wordsPlanetary orbitsasteroidmoon
PlutoUranus Saturn Jupiter Marscomet outer planetgas giant
terrestrial NeptuneEarth Venus Mercuryinner planet Types of planets
Theinner planets Mercury, Venus, Earth, and Mars have rocky
surfaces. They are known as terrestrial or Earthlike planets. The
outer planets Jupiter, Saturn, Uranus, and Neptune are gas giants.
Pluto is a dwarf planet made of rock and ice. The distance of the
planets from the Sun varies from 28.6 million miles (45.9 million
km) for Mercury at its closest to 4,609 million miles (7,375
million km) for Pluto at its farthest. MercuryVenus Earth
MarsJupiterSaturn Uranus Neptune Pluto Los NewAngelesYorkThis map
of part of the United States demonstratesthe relative distances of
the planets from the Sun ifit were located in Los Angeles,
Californiaand Pluto at New York City.Planets mean distance from the
Sun MilesKilometers Mercury 36,000,00057,900,000 Venus 67,200,000
108,100,000 Diagram Visual Information Ltd. Earth 93,000,000
149,700,000 Mars 141,600,000 227,900,000 Jupiter
483,800,000778,600,000 Saturn890,800,0001,436,600,000
Uranus1,784,800,0002,872,600,000 Neptune 2,793,100,0004,494,900,000
Pluto 3,647,200,0005,869,600,000
14. *01 Earth-space (8-25).qxd12/12/0811:05 AMPage 14 14 EARTH
AND SPACEStructure of the Sun Key words Structural view of the Sun
chromospherephotosphere convectionSun core corona nuclear
fusionsolar flareCore convective zone At the heart of the
Sunnuclear fusionreactions convert radiative zonehydrogen
intohelium.
Temperaturesreach27,000,000F(15,000,000C).coreRadiativezone
Energyproduced inthe core radiatestoward the surface ofthe Sun
through thisregion. This energy prevents thephotosphereSun from
collapsing underthe force of gravity. chromosphereConvective
zonecorona Energy waves, weakened by their passage through the
radiative zone, pass through this area via constantly churning
convection currents.Photosphere Thephotoshere surface of the Sun is
highly irregular. Temperatures vary from 7,80016,000F
(4,3009,000C).Nuclear fusion at the Suns coreChromosphere loose
hydrogen nuclei The chromosphere is a highly agitated zone of thin
gases rising to about 6,000 miles (9,700 km) above the photosphere.
This region is constantly disrupted by solar flares, prominences,
hydrogen nuclei combined into helium atom and spiricules. Diagram
Visual Information Ltd.Corona Extendingmillions of miles into
spaceenergy released by fusion reactionthe corona is a very thinly
dispersedball of gas. Atoms and molecules in this regionhave very
high velocities andtemperatures up to 7,000,000F(4,000,000C).
15. *01 Earth-space (8-25).qxd 12/12/08 11:05 AMPage 15 15The
Suns energyEARTH AND SPACE Key wordsNuclear fusionRadiant energy
nuclear 5Wavelengths fusion10(meters)1Nuclear fusion During nuclear
fusion,2 hydrogen atoms fuse toproduce helium. The mass of
heliumproduced is less than themass of the hydrogen3 radio
wavesthat produced it. The mass that is lost isconverted to
energy,given off by the Sun aslight, heat, and invisibleforms of
radiation.4 Radiant energy The Sun radiates energythrough space
atwavelengths in the5 more than electromagnetic90% ofspectrum from
(veryinfraredthe Suns short wavelength) gammaradiantrays to the
longestenergyvisible light longwave radio waves. Gamma rays,
X-rays, andultraviolet rays areshortwave
penetrativeultravioletforms of radiation that6 are potentially
damagingENERGYto living tissue. Visible light comprisesalmost
proton 10% ofwavelengths perceived asthe Suns colors ranging from
violet X-rays radiant neutronthrough red.energygamma Infrared
radiation israysperceived as radiant heat. positron Microwaves
resembleneutrinothose used in microwaveovens. Radio waves from the
Sun 1 Hydrogen nuclei (protons) collide. include waves shorter10-15
2 Collisions throw off two positrons and neutrinos,than those used
for radio Diagram Visual Information Ltd. and form two deuterons
(heavy hydrogen nuclei).broadcasts. 3 Each deuteron collides with a
proton.Most of the Suns visible light can penetratethe whole of the
atmosphere right down to 4 Collisions form light helium nuclei.
Earths surface, except where cloud intervenes. 5 Fusion of light
helium nuclei forms one stable However only some of the infrared
radiationgets through: the rest is cut off, along with helium
nucleus and frees two protons.the most harmful ultraviolet
radiation, by 6 Fusion releases energy.atmospheric gases.
16. *01 Earth-space (8-25).qxd 12/12/0811:05 AMPage 1616EARTH
AND SPACEThe Moon Key wordsThe MoonEarth barycenter axisSunEarth
barycenter Earth Moon orbitCommon center of mass Moon balance point
(barycenter) Both the Moon and Earth travelaround a common center
of massknown as a barycenter. As Earths mass is much greater
thanthe Moons, their barycenter liesThe Moons path around Earth The
Moons path aroundwithin Earths diameter.the SunThe Moons path
TheMoon revolves aroundEarth every 27 days. Italso revolves on
itsown axis once every27 days, so thesame side alwaysfaces Earth.
As Earthrevolvesaround theSun, and theEarths orbitMoonaround Moons
orbitEarth, theMoons patharound theSun resemblesa cogwheel.The
Moons phases Diagram Visual Information Ltd. New Moon Waxing
crescent Half Moon,Waxing gibbous Full MoonWaning gibbous Half
Moon, Waning crescent Moon first quarter MoonMoon last
quarterMoon
17. *01 Earth-space (8-25).qxd 12/12/0811:05 AM Page 1717The
Moon: surfaceEARTH AND SPACELunar seasMare Frigoris Sea of Cold
Mare Imbrium Sea of Showers Mare Serenitatis Sea of SerenityMare
Crisium Mare Vaporum Sea of CrisesOceanus ProcellarumSea of
VaporsOcean of Storms Mare TranquillitatisSea of TranquilityMare
Fecunditatis Sea of FertilityMare NubiumSea of Clouds Mare Nectaris
Sea of Nectar Mare Humorum Sea of MoistureMajor lunar
cratersPlatoCopernicus Comparative sizes of the Moon and
EarthKeplerPtolemaeusGrimaldiLangrenus Diagram Visual Information
Ltd.TychoTheophilusClavius
18. *01 Earth-space (8-25).qxd12/12/08 11:05 AM Page 1818 EARTH
AND SPACE The Moon: structure Key words asteroid mantle basalt
regolith boulder core crust partially-moltenmetal zone 220
miles(350 km) thickThe Moons structure Like Earth, the Moon has a
core,iron-rich coremantle, and crust.with a radius of Unlike Earths
mantle and crust,190 miles (300 km)those of the Moon are
rigid.Structure of a plainrigid mantle This block diagram shows
features600 miles (1,000 km)typical of a basalt lunar plain. Much
of it is covered by regolith: loosedebris from dust to boulders
produced thick crustby old asteroid impacts.45 miles (70 km) thick
fault scarp crater chain volcanoes impact crater Diagram Visual
Information Ltd. regolith (surface debris) impact crater wrinkle
ridge linear rille (shallow rift valley)
19. *01 Earth-space (8-25).qxd 12/12/08 11:05 AM Page 1919Solar
and lunar eclipsesEARTH AND SPACE Key words EarthSun
eclipseumbraSolar eclipsesarea of partial eclipse: sunlight is
partially blocked by the Moon MoonTotal eclipsearea of totality:
sunlight is completely blocked by the Moonpenumbra planetEclipse
Aneclipse occurs when oneSunEarthheavenly body blocks the
lightshining from a second onto athird.Moon at perigee of
orbitSolar eclipseAsolar eclipse happens whenPartial eclipse the
Moon comes between theSun and Earth. This kind ofeclipse occurs on
Earth at area of partial eclipseplaces crossed by the
Moonsshadow.total eclipse shadow misses Earth Where the Moon
completelySunEarthblots out the Sun, the umbra,the darkest part of
the Moonsshadow, produces a totaleclipse. Here the sky becomesdark
as if it were night. Moon Where the Moon concealsonly part of the
Sun, its partialshadow or penumbraproduces a partial eclipse.Lunar
eclipsesTotal eclipseMoon enters Earths total shadow Lunar eclipseA
lunar eclipse happens when total shadow cast by EarthEarth passes
between the Sunand the Moon. If Earth completely blots outthe Sun,
Earths umbraSunEarthproduces a total eclipse ofthe Moon. If only
Earths penumbra fallson the Moon, the latter ispartially eclipsed
from theposition of an observer onEarth.Partial eclipse partial
shadow cast by Earth During most lunar eclipses,the Moon remains
visible fromtotal shadow cast by EarthEarth as it receives
somesunlight bent by Earths Diagram Visual Information
Ltd.atmosphere.SunEarth Moon enters Earths partial shadow
20. *01 Earth-space (8-25).qxd 12/12/08 11:05 AM Page 2020EARTH
AND SPACE Structure of Earth Key words Structure of Earth core rock
During Earths formation, heavy elementsEarths outer core may be
mainly iron crust moved toward the center, while lightand nickel
with some silicon. Earth ones gathered at the surface. Part of the
mantle is semimolten and element The hot, high-pressure core is
mainly flows in sluggish currents. mantle solid iron and nickel. A
crust of relatively light rocks rests on the
mantle.Compositionsolid metal inner core with a radius of1,000
miles (1,600 km) molten outer core 1,140 miles (1,820 km)
thicksemimolten rocky lower mantle1,430 miles (2,290 km) thick
upper mantle 390 miles (640 km) thick crust 6.2525 miles (1040 km)
thickEarth facts Earthis the only planet in thesolar system known
to support life.Earths crust Earth takes 365.25 days to orbit the
Earths crust is a shell of solid rock that floats on a sea of
molten magma.Sun (that is, one year).continental crust Diagram
Visual Information Ltd. It spins on its own axis every 23 hours56
minutes (one day).lithosphere The average temperature on the
magmasurface is about 59F (15C). Earth is the only planet to have
liquidwater on its surface. Earth has one natural satellite,
oceanic crustthe Moon.
21. *01 Earth-space (8-25).qxd12/12/0811:05 AM Page 21 21Earths
magnetic field EARTH AND SPACEKey wordsEarths magnetic
fieldcoremagnetic North Pole geographic North Pole
EarthgeomagnetismEarths mantle Earths corelines of force Earth as a
magnet Earthscrust and mantle rotate rather faster than its
metallic core. This difference in speed produces a dynamo effect
creating an immense magnetic field. This geomagnetic field consists
of imaginary flux lines (lines of magneticlines of force force)
that curve around Earth between its north and south magnetic poles.
Compass needles point to thegeographic South Polemagnetic poles.
magnetic South Pole The magnetic poles do not coincide with the
geographic poles, and theirInside Earth inner core rotation
positions shift through time.eddies in theouter core Regional
variations Earths magnetic field varies in intensity from place to
place across the planets surface. Its intensity is greatestrotation
of mantle near the magnetic poles.The planet sectioned Local
variations indicate differences inat the equator showsinternal
differences subsurface rocks.of rotation producingthe magnetic
field.Regional variationsVariations in strength of Earths magnetic
field from 1 (high) to 11 (low) 34 3 4 5 6 7 8 9 89 10 6 Diagram
Visual Information Ltd.11 5 4 3 2 1