Plate tectonics

The tectonic plates of the world were mapped in the second halfof the 20th century.

Remnants of the Farallon Plate, deep in Earth’s mantle. It isthought that much of the plate initially went under North America(particularly the western United States and southwest Canada) ata very shallow angle, creating much of the mountainous terrainin the area (particularly the southern Rocky Mountains).

Plate tectonics (from the Late Latin tectonicus, fromthe Greek: τεκτονικός “pertaining to building”)[1] is ascientific theory that describes the large-scale motion ofEarth's lithosphere. This theoretical model builds onthe concept of continental drift which was developedduring the first few decades of the 20th century. Thegeoscientific community accepted the theory after theconcepts of seafloor spreading were later developed in thelate 1950s and early 1960s.The lithosphere, which is the rigid outermost shell of aplanet (on Earth, the crust and upper mantle), is bro-ken up into tectonic plates. On Earth, there are seven oreight major plates (depending on how they are defined)and many minor plates. Where plates meet, their rela-

tive motion determines the type of boundary; convergent,divergent, or transform. Earthquakes, volcanic activity,mountain-building, and oceanic trench formation occuralong these plate boundaries. The lateral relative move-ment of the plates typically varies from zero to 100 mmannually.[2]

Tectonic plates are composed of oceanic lithosphere andthicker continental lithosphere, each topped by its ownkind of crust. Along convergent boundaries, subductioncarries plates into the mantle; the material lost is roughlybalanced by the formation of new (oceanic) crust alongdivergent margins by seafloor spreading. In this way, thetotal surface of the globe remains the same. This predic-tion of plate tectonics is also referred to as the conveyorbelt principle. Earlier theories (that still have some sup-porters) propose gradual shrinking (contraction) or grad-ual expansion of the globe.[3]

Tectonic plates are able to move because the Earth’slithosphere has greater strength than the underlyingasthenosphere. Lateral density variations in the mantleresult in convection. Plate movement is thought to bedriven by a combination of the motion of the seaflooraway from the spreading ridge (due to variations in topog-raphy and density of the crust, which result in differencesin gravitational forces) and drag, with downward suction,at the subduction zones. Another explanation lies in thedifferent forces generated by the rotation of the globe andthe tidal forces of the Sun and Moon. The relative im-portance of each of these factors and their relationship toeach other is unclear, and still the subject of much debate.

1 Key principles

The outer layers of the Earth are divided into thelithosphere and asthenosphere. This is based on differ-ences in mechanical properties and in the method for thetransfer of heat. Mechanically, the lithosphere is coolerand more rigid, while the asthenosphere is hotter andflows more easily. In terms of heat transfer, the litho-sphere loses heat by conduction, whereas the astheno-sphere also transfers heat by convection and has a nearlyadiabatic temperature gradient. This division should notbe confused with the chemical subdivision of these samelayers into themantle (comprising both the asthenosphereand the mantle portion of the lithosphere) and the crust:a given piece of mantle may be part of the lithosphereor the asthenosphere at different times depending on itstemperature and pressure.

1

2 2 TYPES OF PLATE BOUNDARIES

The key principle of plate tectonics is that the litho-sphere exists as separate and distinct tectonic plates, whichride on the fluid-like (visco-elastic solid) asthenosphere.Plate motions range up to a typical 10–40 mm/year (Mid-Atlantic Ridge; about as fast as fingernails grow), to about160mm/year (Nazca Plate; about as fast as hair grows).[4]The driving mechanism behind this movement is de-scribed below.Tectonic lithosphere plates consist of lithospheric mantleoverlain by either or both of two types of crustal mate-rial: oceanic crust (in older texts called sima from siliconand magnesium) and continental crust (sial from siliconand aluminium). Average oceanic lithosphere is typically100 km (62 mi) thick;[5] its thickness is a function of itsage: as time passes, it conductively cools and subjacentcooling mantle is added to its base. Because it is formedat mid-ocean ridges and spreads outwards, its thicknessis therefore a function of its distance from the mid-oceanridge where it was formed. For a typical distance thatoceanic lithosphere must travel before being subducted,the thickness varies from about 6 km (4 mi) thick at mid-ocean ridges to greater than 100 km (62mi) at subductionzones; for shorter or longer distances, the subduction zone(and therefore also the mean) thickness becomes smalleror larger, respectively.[6] Continental lithosphere is typi-cally ~200 km thick, though this varies considerably be-tween basins, mountain ranges, and stable cratonic inte-riors of continents. The two types of crust also differin thickness, with continental crust being considerablythicker than oceanic (35 km vs. 6 km).[7]

The location where two plates meet is called a plateboundary. Plate boundaries are commonly associ-ated with geological events such as earthquakes andthe creation of topographic features such as mountains,volcanoes, mid-ocean ridges, and oceanic trenches. Themajority of the world’s active volcanoes occur along plateboundaries, with the Pacific Plate’s Ring of Fire being themost active and widely known today. These boundariesare discussed in further detail below. Some volcanoesoccur in the interiors of plates, and these have been var-iously attributed to internal plate deformation[8] and tomantle plumes.As explained above, tectonic plates may include conti-nental crust or oceanic crust, and most plates containboth. For example, the African Plate includes the con-tinent and parts of the floor of the Atlantic and IndianOceans. The distinction between oceanic crust and con-tinental crust is based on their modes of formation.Oceanic crust is formed at sea-floor spreading centers,and continental crust is formed through arc volcanism andaccretion of terranes through tectonic processes, thoughsome of these terranes may contain ophiolite sequences,which are pieces of oceanic crust considered to be part ofthe continent when they exit the standard cycle of forma-tion and spreading centers and subduction beneath conti-nents. Oceanic crust is also denser than continental crustowing to their different compositions. Oceanic crust is

denser because it has less silicon and more heavier ele-ments ("mafic") than continental crust ("felsic").[9] As aresult of this density stratification, oceanic crust gener-ally lies below sea level (for example most of the PacificPlate), while continental crust buoyantly projects abovesea level (see the page isostasy for explanation of thisprinciple).

2 Types of plate boundaries

Main article: List of tectonic plate interactions

Three types of plate boundaries exist,[10] with a fourth,mixed type, characterized by the way the plates move rel-ative to each other. They are associated with differenttypes of surface phenomena. The different types of plateboundaries are:[11][12]

1. Transform boundaries (Conservative) occur wheretwo lithospheric plates slide, or perhaps more accu-rately, grind past each other along transform faults,where plates are neither created nor destroyed. Therelative motion of the two plates is either sinistral(left side toward the observer) or dextral (right sidetoward the observer). Transform faults occur acrossa spreading center. Strong earthquakes can occuralong a fault. The San Andreas Fault in Californiais an example of a transform boundary exhibitingdextral motion.

2. Divergent boundaries (Constructive) occur wheretwo plates slide apart from each other. At zones ofocean-to-ocean rifting, divergent boundaries formby seafloor spreading, allowing for the formation ofnew ocean basin. As the continent splits, the ridgeforms at the spreading center, the ocean basin ex-pands, and finally, the plate area increases causingmany small volcanoes and/or shallow earthquakes.At zones of continent-to-continent rifting, divergentboundaries may cause new ocean basin to form asthe continent splits, spreads, the central rift col-lapses, and ocean fills the basin. Active zonesof Mid-ocean ridges (e.g., Mid-Atlantic Ridge andEast Pacific Rise), and continent-to-continent rifting(such as Africa’s East African Rift and Valley, RedSea) are examples of divergent boundaries.

3. Convergent boundaries (Destructive) (or active mar-gins) occur where two plates slide toward each otherto form either a subduction zone (one plate mov-ing underneath the other) or a continental colli-sion. At zones of ocean-to-continent subduction(e.g., Western South America, and Cascade Moun-tains in Western United States), the dense oceaniclithosphere plunges beneath the less dense continent.Earthquakes then trace the path of the downward-moving plate as it descends into asthenosphere, a

3.1 Driving forces related to mantle dynamics 3

trench forms, and as the subducted plate partiallymelts, magma rises to form continental volcanoes.At zones of ocean-to-ocean subduction (e.g., theAndes mountain range in South America, Aleutianislands, Mariana islands, and the Japanese islandarc), older, cooler, denser crust slips beneath lessdense crust. This causes earthquakes and a deeptrench to form in an arc shape. The upper mantleof the subducted plate then heats and magma risesto form curving chains of volcanic islands. Deepmarine trenches are typically associated with sub-duction zones, and the basins that develop along theactive boundary are often called “foreland basins”.The subducting slab contains many hydrous min-erals which release their water on heating. Thiswater then causes the mantle to melt, producingvolcanism. Closure of ocean basins can occur atcontinent-to-continent boundaries (e.g., Himalayasand Alps): collision between masses of granitic con-tinental lithosphere; neither mass is subducted; plateedges are compressed, folded, uplifted.

4. Plate boundary zones occur where the effects of theinteractions are unclear, and the boundaries, usuallyoccurring along a broad belt, are not well defined andmay show various types of movements in differentepisodes.

Three types of plate boundary.

3 Driving forces of plate motion

Plate tectonics is basically a kinematic phenomenon. Sci-entists agree on the observation and deduction that theplates have moved with respect to one another but con-tinue to debate as to how and when. A major questionremains as to what geodynamic mechanism motors platemovement. Here, science diverges in different theories.It is generally accepted that tectonic plates are able tomove because of the relative density of oceanic litho-sphere and the relative weakness of the asthenosphere.Dissipation of heat from the mantle is acknowledged tobe the original source of the energy required to drive platetectonics through convection or large scale upwelling anddoming. The current view, though still a matter of some

Plate motion based on Global Positioning System (GPS) satellitedata from NASA JPL. The vectors show direction and magnitudeof motion.

debate, asserts that as a consequence, a powerful sourceof plate motion is generated due to the excess densityof the oceanic lithosphere sinking in subduction zones.When the new crust forms at mid-ocean ridges, thisoceanic lithosphere is initially less dense than the under-lying asthenosphere, but it becomes denser with age as itconductively cools and thickens. The greater density ofold lithosphere relative to the underlying asthenosphereallows it to sink into the deep mantle at subduction zones,providing most of the driving force for plate movement.The weakness of the asthenosphere allows the tectonicplates to move easily towards a subduction zone.[13] Al-though subduction is believed to be the strongest forcedriving plate motions, it cannot be the only force sincethere are plates such as the North American Plate whichare moving, yet are nowhere being subducted. The sameis true for the enormous Eurasian Plate. The sources ofplate motion are a matter of intensive research and dis-cussion among scientists. One of the main points is thatthe kinematic pattern of the movement itself should beseparated clearly from the possible geodynamic mecha-nism that is invoked as the driving force of the observedmovement, as some patterns may be explained by morethan one mechanism.[14] In short, the driving forces advo-cated at the moment can be divided into three categoriesbased on the relationship to the movement: mantle dy-namics related, gravity related (mostly secondary forces),and Earth rotation related.

3.1 Driving forces related to mantle dy-namics

Main article: Mantle convection

Formuch of the last quarter century, the leading theory ofthe driving force behind tectonic plate motions envisagedlarge scale convection currents in the upper mantle whichare transmitted through the asthenosphere. This theorywas launched by Arthur Holmes and some forerunners

4 3 DRIVING FORCES OF PLATE MOTION

in the 1930s[15] and was immediately recognized as thesolution for the acceptance of the theory as originallydiscussed in the papers of Alfred Wegener in the earlyyears of the century. However, despite its acceptance, itwas long debated in the scientific community because theleading (“fixist”) theory still envisaged a static Earth with-out moving continents up until the major break–throughsof the early sixties.Two– and three–dimensional imaging of Earth’s inte-rior (seismic tomography) shows a varying lateral den-sity distribution throughout the mantle. Such densityvariations can be material (from rock chemistry), min-eral (from variations in mineral structures), or thermal(through thermal expansion and contraction from heat en-ergy). The manifestation of this varying lateral density ismantle convection from buoyancy forces.[16]

How mantle convection directly and indirectly relates toplate motion is a matter of ongoing study and discus-sion in geodynamics. Somehow, this energy must betransferred to the lithosphere for tectonic plates to move.There are essentially two types of forces that are thoughtto influence plate motion: friction and gravity.

• Basal drag (friction): Plate motion driven by fric-tion between the convection currents in the astheno-sphere and the more rigid overlying lithosphere.

• Slab suction (gravity): Plate motion driven by localconvection currents that exert a downward pull onplates in subduction zones at ocean trenches. Slabsuction may occur in a geodynamic setting wherebasal tractions continue to act on the plate as it divesinto the mantle (although perhaps to a greater extentacting on both the under and upper side of the slab).

Lately, the convection theory has been much debated asmodern techniques based on 3D seismic tomography stillfail to recognize these predicted large scale convectioncells. Therefore, alternative views have been proposed:In the theory of plume tectonics developed during the1990s, a modified concept of mantle convection currentsis used. It asserts that super plumes rise from the deepermantle and are the drivers or substitutes of the major con-vection cells. These ideas, which find their roots in theearly 1930s with the so-called “fixistic” ideas of the Euro-pean and Russian Earth Science Schools, find resonancein the modern theories which envisage hot spots/mantleplumes which remain fixed and are overridden by oceanicand continental lithosphere plates over time and leavetheir traces in the geological record (though these phe-nomena are not invoked as real driving mechanisms, butrather as modulators). Modern theories that continuebuilding on the older mantle doming concepts and seeplate movements as a secondary phenomena are beyondthe scope of this page and are discussed elsewhere (forexample on the plume tectonics page).Another theory is that the mantle flows neither in cells

nor large plumes but rather as a series of channels justbelow the Earth’s crust which then provide basal frictionto the lithosphere. This theory is called “surge tectonics”and became quite popular in geophysics and geodynamicsduring the 1980s and 1990s.[17]

3.2 Driving forces related to gravity

Forces related to gravity are usually invoked as secondaryphenomena within the framework of a more general driv-ing mechanism such as the various forms of mantle dy-namics described above.Gravitational sliding away from a spreading ridge: Ac-cording to many authors, plate motion is driven by thehigher elevation of plates at ocean ridges.[18] As oceaniclithosphere is formed at spreading ridges from hot man-tle material, it gradually cools and thickens with age (andthus adds distance from the ridge). Cool oceanic litho-sphere is significantly denser than the hot mantle materialfrom which it is derived and so with increasing thicknessit gradually subsides into the mantle to compensate thegreater load. The result is a slight lateral incline with in-creased distance from the ridge axis.This force is regarded as a secondary force and is oftenreferred to as "ridge push". This is a misnomer as noth-ing is “pushing” horizontally and tensional features aredominant along ridges. It is more accurate to refer tothis mechanism as gravitational sliding as variable topog-raphy across the totality of the plate can vary consider-ably and the topography of spreading ridges is only themost prominent feature. Other mechanisms generatingthis gravitational secondary force include flexural bulgingof the lithosphere before it dives underneath an adjacentplate which produces a clear topographical feature thatcan offset, or at least affect, the influence of topographi-cal ocean ridges, and mantle plumes and hot spots, whichare postulated to impinge on the underside of tectonicplates.Slab-pull: Current scientific opinion is that the astheno-sphere is insufficiently competent or rigid to directlycause motion by friction along the base of the lithosphere.Slab pull is therefore most widely thought to be the great-est force acting on the plates. In this current understand-ing, plate motion is mostly driven by the weight of cold,dense plates sinking into the mantle at trenches.[19] Re-cent models indicate that trench suction plays an impor-tant role as well. However, as the North American Plateis nowhere being subducted, yet it is in motion presents aproblem. The same holds for the African, Eurasian, andAntarctic plates.Gravitational sliding away from mantle doming: Accord-ing to older theories, one of the driving mechanismsof the plates is the existence of large scale astheno-sphere/mantle domes which cause the gravitational slid-ing of lithosphere plates away from them. This gravita-tional sliding represents a secondary phenomenon of this

3.4 Relative significance of each driving force mechanism 5

basically vertically oriented mechanism. This can act onvarious scales, from the small scale of one island arc upto the larger scale of an entire ocean basin.[20]

3.3 Driving forces related to Earth rota-tion

Alfred Wegener, being a meteorologist, had proposedtidal forces and pole flight force as themain drivingmech-anisms behind continental drift; however, these forceswere considered far too small to cause continental motionas the concept then was of continents plowing throughoceanic crust.[21] Therefore, Wegener later changed hisposition and asserted that convection currents are themain driving force of plate tectonics in the last editionof his book in 1929.However, in the plate tectonics context (accepted sincethe seafloor spreading proposals of Heezen, Hess, Dietz,Morley, Vine, and Matthews (see below) during the early1960s), oceanic crust is suggested to be inmotionwith thecontinents which caused the proposals related to Earth ro-tation to be reconsidered. In more recent literature, thesedriving forces are:

1. Tidal drag due to the gravitational force the Moon(and the Sun) exerts on the crust of the Earth[22]

2. Shear strain of the Earth globe due to N-S compres-sion related to its rotation and modulations;

3. Pole flight force: equatorial drift due to rotation andcentrifugal effects: tendency of the plates to movefrom the poles to the equator ("Polflucht");

4. The Coriolis effect acting on plates when they movearound the globe;

5. Global deformation of the geoid due to small dis-placements of rotational pole with respect to theEarth’s crust;

6. Other smaller deformation effects of the crust due towobbles and spin movements of the Earth rotationon a smaller time scale.

For these mechanisms to be overall valid, systematic re-lationships should exist all over the globe between theorientation and kinematics of deformation and the geo-graphical latitudinal and longitudinal grid of the Earth it-self. Ironically, these systematic relations studies in thesecond half of the nineteenth century and the first halfof the twentieth century underline exactly the opposite:that the plates had not moved in time, that the deforma-tion grid was fixed with respect to the Earth equator andaxis, and that gravitational driving forces were generallyacting vertically and caused only local horizontal move-ments (the so-called pre-plate tectonic, “fixist theories”).Later studies (discussed below on this page), therefore,

invoked many of the relationships recognized during thispre-plate tectonics period to support their theories (seethe anticipations and reviews in the work of van Dijk andcollaborators).[23]

Of the many forces discussed in this paragraph, tidalforce is still highly debated and defended as a possi-ble principle driving force of plate tectonics. The otherforces are only used in global geodynamic models not us-ing plate tectonics concepts (therefore beyond the discus-sions treated in this section) or proposed as minor modu-lations within the overall plate tectonics model.In 1973, George W. Moore[24] of the USGS and R. C.Bostrom[25] presented evidence for a general westwarddrift of the Earth’s lithosphere with respect to the man-tle. He concluded that tidal forces (the tidal lag or “fric-tion”) caused by the Earth’s rotation and the forces actingupon it by the Moon are a driving force for plate tecton-ics. As the Earth spins eastward beneath the moon, themoon’s gravity ever so slightly pulls the Earth’s surfacelayer back westward, just as proposed by AlfredWegener(see above). In a more recent 2006 study,[26] scientistsreviewed and advocated these earlier proposed ideas. Ithas also been suggested recently in Lovett (2006) thatthis observation may also explain why Venus and Marshave no plate tectonics, as Venus has no moon and Mars’moons are too small to have significant tidal effects onthe planet. In a recent paper,[27] it was suggested that, onthe other hand, it can easily be observed that many platesare moving north and eastward, and that the dominantlywestward motion of the Pacific ocean basins derives sim-ply from the eastward bias of the Pacific spreading cen-ter (which is not a predicted manifestation of such lunarforces). In the same paper the authors admit, however,that relative to the lower mantle, there is a slight westwardcomponent in the motions of all the plates. They demon-strated though that the westward drift, seen only for thepast 30 Ma, is attributed to the increased dominance ofthe steadily growing and accelerating Pacific plate. Thedebate is still open.

3.4 Relative significance of each drivingforce mechanism

The actual vector of a plate’s motion is a function of allthe forces acting on the plate; however, therein lies theproblem regarding what degree each process contributesto the overall motion of each tectonic plate.The diversity of geodynamic settings and the propertiesof each plate must clearly result from differences in thedegree to which multiple processes are actively drivingeach individual plate. One method of dealing with thisproblem is to consider the relative rate at which each plateis moving and to consider the available evidence of eachdriving force on the plate as far as possible.One of the most significant correlations found is thatlithospheric plates attached to downgoing (subducting)

6 4 DEVELOPMENT OF THE THEORY

plates move much faster than plates not attached to sub-ducting plates. The Pacific plate, for instance, is essen-tially surrounded by zones of subduction (the so-calledRing of Fire) and moves much faster than the plates ofthe Atlantic basin, which are attached (perhaps one couldsay 'welded') to adjacent continents instead of subduct-ing plates. It is thus thought that forces associated withthe downgoing plate (slab pull and slab suction) are thedriving forces which determine the motion of plates, ex-cept for those plates which are not being subducted.[19]The driving forces of plate motion continue to be ac-tive subjects of on-going research within geophysics andtectonophysics.

4 Development of the theory

Further information: Timeline of the development oftectonophysics

4.1 Summary

Alps

Persia - Tibet - Burma

Ninety East - Sumatra

Philippines

Laptev Sea

western Aleutians

Alaska - Yukon

Gorda-California-Nevada

Rivera-Cocos

west central Atlantic

Peru

Puna-Sierras

Pampeanas

New Hebrides - Fiji

Africa (AF)Arabia (AR)

Eurasia (EU)

India (IN)

Somalia (SO)

Antarctica (AN)

Australia (AU)

Sunda (SU)

Philippine Sea (PS)

Caroline (CL)

Pacific (PA)

Yangtze (YA)

Amur (AM)

Okhotsk (OK)

Eurasia (EU)

Pacific (PA)

Pacific (PA)

Pacific (PA)

Pacific (PA)

Antarctica (AN)

MS

BS

BH

MOWL SB

SSTI

ONOkinawa

Mariana

MA

CR

BR

NH

FT

NI

TO

Tonga

KermadecKE

Aegean Sea

AS

AT

Anatolia

BU

Burma

NB

Manus (MN)

Juan de Fuca

JF

North America (NA)

Caribbean (CA)

Cocos (CO)

RiveraRI

Galápagos (GP) North Andes

NDPA

Panama

Nazca (NZ)

EasterEA

JZJuan Fernandez

Antarctica (AN)Scotia (SC)

ShetlandSL

SW

Sandwich

South America (SA)

Altiplano

AP

Antarctica (AN)

Eurasia (EU)

Africa (AF)

14

15

37

21

7

11 13

29

20

26

13

13

12

59

36

14

14

10

15

48

54

71

69

84

51

39

87

14

92 70 96

58

70

6968

10

12

66

56

78

62

55

1008386

26

102

92

13

18

16

59

90

103

62119

44

82

1414

102

51

5183

95

69

25

26

19

22

10

67

40

19

51

53

14

13

25

3131

34

26

32

27

11

24

19

158

5

47

34

6

11

46

17

57

44

15

76

18

23

10

14

10

96

70

14

14

32

Equator

OCEAN

PACIFIC

OCEAN

ATLANTIC

INDIAN

OCEAN

AUSTRAL OCEAN AUSTRAL OCEAN

continental / oceanic convergent boundary

continental rift boundary / oceanic spreading ridge

continental / oceanic transform fault

subduction zone

velocity with respect to Africa (mm/y)

orogenyAlps

30

Detailed map showing the tectonic plates with their movementvectors.

In line with other previous and contemporaneous propos-als, in 1912 the meteorologist Alfred Wegener amply de-scribed what he called continental drift, expanded in his1915 book The Origin of Continents and Oceans[28] andthe scientific debate started that would end up fifty yearslater in the theory of plate tectonics.[29] Starting from theidea (also expressed by his forerunners) that the presentcontinents once formed a single land mass (which wascalled Pangea later on) that drifted apart, thus releas-ing the continents from the Earth’s mantle and likeningthem to “icebergs” of low density granite floating on asea of denser basalt.[30] Supporting evidence for the ideacame from the dove-tailing outlines of South America’seast coast and Africa’s west coast, and from the match-ing of the rock formations along these edges. Confirma-tion of their previous contiguous nature also came fromthe fossil plants Glossopteris and Gangamopteris, and thetherapsid or mammal-like reptile Lystrosaurus, all widelydistributed over South America, Africa, Antarctica, Indiaand Australia. The evidence for such an erstwhile joiningof these continents was patent to field geologists working

in the southern hemisphere. The South African Alex duToit put together a mass of such information in his 1937publication Our Wandering Continents, and went furtherthan Wegener in recognising the strong links between theGondwana fragments.But without detailed evidence and a force sufficient todrive the movement, the theory was not generally ac-cepted: the Earth might have a solid crust and mantle anda liquid core, but there seemed to be no way that portionsof the crust could move around. Distinguished scientists,such as Harold Jeffreys and Charles Schuchert, were out-spoken critics of continental drift.Despite much opposition, the view of continental driftgained support and a lively debate started between“drifters” or “mobilists” (proponents of the theory) and“fixists” (opponents). During the 1920s, 1930s and1940s, the former reached important milestones propos-ing that convection currents might have driven the platemovements, and that spreading may have occurred belowthe sea within the oceanic crust. Concepts close to theelements now incorporated in plate tectonics were pro-posed by geophysicists and geologists (both fixists andmobilists) like Vening-Meinesz, Holmes, and Umbgrove.One of the first pieces of geophysical evidence that wasused to support the movement of lithospheric plates camefrom paleomagnetism. This is based on the fact that rocksof different ages show a variable magnetic field direction,evidenced by studies since the mid–nineteenth century.The magnetic north and south poles reverse through time,and, especially important in paleotectonic studies, the rel-ative position of the magnetic north pole varies throughtime. Initially, during the first half of the twentieth cen-tury, the latter phenomenon was explained by introduc-ing what was called “polar wander” (see apparent polarwander), i.e., it was assumed that the north pole locationhad been shifting through time. An alternative explana-tion, though, was that the continents had moved (shiftedand rotated) relative to the north pole, and each conti-nent, in fact, shows its own “polar wander path”. Duringthe late 1950s it was successfully shown on two occasionsthat these data could show the validity of continental drift:by Keith Runcorn in a paper in 1956,[31] and by WarrenCarey in a symposium held in March 1956.[32]

The second piece of evidence in support of continentaldrift came during the late 1950s and early 60s from dataon the bathymetry of the deep ocean floors and the na-ture of the oceanic crust such as magnetic properties and,more generally, with the development of marine geol-ogy[33] which gave evidence for the association of seafloorspreading along themid-oceanic ridges andmagnetic fieldreversals, published between 1959 and 1963 by Heezen,Dietz, Hess, Mason, Vine & Matthews, and Morley.[34]

Simultaneous advances in early seismic imaging tech-niques in and around Wadati-Benioff zones along thetrenches bounding many continental margins, togetherwith many other geophysical (e.g. gravimetric) and geo-

4.3 Floating continents, paleomagnetism, and seismicity zones 7

logical observations, showed how the oceanic crust coulddisappear into the mantle, providing the mechanism tobalance the extension of the ocean basins with shorteningalong its margins.All this evidence, both from the ocean floor and from thecontinental margins, made it clear around 1965 that conti-nental drift was feasible and the theory of plate tectonics,which was defined in a series of papers between 1965and 1967, was born, with all its extraordinary explana-tory and predictive power. The theory revolutionized theEarth sciences, explaining a diverse range of geologicalphenomena and their implications in other studies such aspaleogeography and paleobiology.

4.2 Continental drift

For more details on this topic, see Continental drift.

In the late 19th and early 20th centuries, geologists as-sumed that the Earth’s major features were fixed, and thatmost geologic features such as basin development andmountain ranges could be explained by vertical crustalmovement, described in what is called the geosynclinaltheory. Generally, this was placed in the context of acontracting planet Earth due to heat loss in the course ofa relatively short geological time.

Alfred Wegener in Greenland in the winter of 1912-13.

It was observed as early as 1596 that the opposite coastsof the Atlantic Ocean—or, more precisely, the edges ofthe continental shelves—have similar shapes and seem tohave once fitted together.[35]

Since that time many theories were proposed to explainthis apparent complementarity, but the assumption ofa solid Earth made these various proposals difficult toaccept.[36]

The discovery of radioactivity and its associated heatingproperties in 1895 prompted a re-examination of the ap-parent age of the Earth.[37] This had previously been esti-mated by its cooling rate and assumption the Earth’s sur-face radiated like a black body.[38] Those calculations had

implied that, even if it started at red heat, the Earth wouldhave dropped to its present temperature in a few tens ofmillions of years. Armed with the knowledge of a newheat source, scientists realized that the Earth would bemuch older, and that its core was still sufficiently hot tobe liquid.By 1915, after having published a first article in 1912,[39]Alfred Wegener was making serious arguments for theidea of continental drift in the first edition of The Ori-gin of Continents and Oceans.[28] In that book (re-issuedin four successive editions up to the final one in 1936),he noted how the east coast of South America and thewest coast of Africa looked as if they were once attached.Wegener was not the first to note this (Abraham Ortelius,Antonio Snider-Pellegrini, Eduard Suess, Roberto Man-tovani and Frank Bursley Taylor preceded him just tomention a few), but he was the first to marshal signifi-cant fossil and paleo-topographical and climatological ev-idence to support this simple observation (and was sup-ported in this by researchers such as Alex du Toit). Fur-thermore, when the rock strata of the margins of sep-arate continents are very similar it suggests that theserocks were formed in the same way, implying that theywere joined initially. For instance, parts of Scotlandand Ireland contain rocks very similar to those foundin Newfoundland and New Brunswick. Furthermore,the Caledonian Mountains of Europe and parts of theAppalachian Mountains of North America are very sim-ilar in structure and lithology.However, his ideas were not taken seriously bymany geol-ogists, who pointed out that there was no apparent mech-anism for continental drift. Specifically, they did not seehow continental rock could plow through themuch denserrock that makes up oceanic crust. Wegener could not ex-plain the force that drove continental drift, and his vindi-cation did not come until after his death in 1930.

4.3 Floating continents, paleomagnetism,and seismicity zones

Global earthquake epicenters, 1963–1998

As it was observed early that although granite existed oncontinents, seafloor seemed to be composed of denser

8 4 DEVELOPMENT OF THE THEORY

basalt, the prevailing concept during the first half of thetwentieth century was that there were two types of crust,named “sial” (continental type crust) and “sima” (oceanictype crust). Furthermore, it was supposed that a staticshell of strata was present under the continents. It there-fore looked apparent that a layer of basalt (sial) underliesthe continental rocks.However, based on abnormalities in plumb line deflec-tion by the Andes in Peru, Pierre Bouguer had deducedthat less-dense mountains must have a downward projec-tion into the denser layer underneath. The concept thatmountains had “roots” was confirmed by George B. Airya hundred years later, during study of Himalayan grav-itation, and seismic studies detected corresponding den-sity variations. Therefore, by the mid-1950s, the questionremained unresolved as to whether mountain roots wereclenched in surrounding basalt or were floating on it likean iceberg.During the 20th century, improvements in and greater useof seismic instruments such as seismographs enabled sci-entists to learn that earthquakes tend to be concentratedin specific areas, most notably along the oceanic trenchesand spreading ridges. By the late 1920s, seismologistswere beginning to identify several prominent earthquakezones parallel to the trenches that typically were inclined40–60° from the horizontal and extended several hun-dred kilometers into the Earth. These zones later becameknown asWadati-Benioff zones, or simply Benioff zones,in honor of the seismologists who first recognized them,Kiyoo Wadati of Japan and Hugo Benioff of the UnitedStates. The study of global seismicity greatly advanced inthe 1960s with the establishment of the Worldwide Stan-dardized Seismograph Network (WWSSN)[40] to mon-itor the compliance of the 1963 treaty banning above-ground testing of nuclear weapons. The much improveddata from the WWSSN instruments allowed seismolo-gists to map precisely the zones of earthquake concen-tration world wide.Meanwhile, debates developed around the phenomena ofpolar wander. Since the early debates of continental drift,scientists had discussed and used evidence that polar drifthad occurred because continents seemed to have movedthrough different climatic zones during the past. Fur-thermore, paleomagnetic data had shown that the mag-netic pole had also shifted during time. Reasoning in anopposite way, the continents might have shifted and ro-tated, while the pole remained relatively fixed. The firsttime the evidence of magnetic polar wander was used tosupport the movements of continents was in a paper byKeith Runcorn in 1956,[31] and successive papers by himand his students Ted Irving (who was actually the first tobe convinced of the fact that paleomagnetism supportedcontinental drift) and Ken Creer.This was immediately followed by a symposium inTasmania in March 1956.[41] In this symposium, the evi-dence was used in the theory of an expansion of the global

crust. In this hypothesis the shifting of the continents canbe simply explained by a large increase in size of the Earthsince its formation. However, this was unsatisfactory be-cause its supporters could offer no convincing mechanismto produce a significant expansion of the Earth. Certainlythere is no evidence that the moon has expanded in thepast 3 billion years; other work would soon show that theevidence was equally in support of continental drift on aglobe with a stable radius.During the thirties up to the late fifties, works by Vening-Meinesz, Holmes, Umbgrove, and numerous others out-lined concepts that were close or nearly identical to mod-ern plate tectonics theory. In particular, the English ge-ologist Arthur Holmes proposed in 1920 that plate junc-tions might lie beneath the sea, and in 1928 that con-vection currents within the mantle might be the driv-ing force.[42] Often, these contributions are forgotten be-cause:

• At the time, continental drift was not accepted.

• Some of these ideas were discussed in the context ofabandoned fixistic ideas of a deforming globe with-out continental drift or an expanding Earth.

• They were published during an episode of extremepolitical and economic instability that hampered sci-entific communication.

• Many were published by European scientists and atfirst not mentioned or given little credit in the paperson sea floor spreading published by the Americanresearchers in the 1960s.

4.4 Mid-oceanic ridge spreading and con-vection

For more details on Mid-ocean ridge, see Seafloorspreading.

In 1947, a team of scientists led by Maurice Ewing utiliz-ing the Woods Hole Oceanographic Institution's researchvessel Atlantis and an array of instruments, confirmedthe existence of a rise in the central Atlantic Ocean, andfound that the floor of the seabed beneath the layer ofsediments consisted of basalt, not the granite which is themain constituent of continents. They also found that theoceanic crust was much thinner than continental crust.All these new findings raised important and intriguingquestions.[43]

The new data that had been collected on the oceanbasins also showed particular characteristics regardingthe bathymetry. One of the major outcomes of thesedatasets was that all along the globe, a system of mid-oceanic ridges was detected. An important conclusionwas that along this system, new ocean floor was being cre-ated, which led to the concept of the "Great Global Rift".

4.5 Magnetic striping 9

This was described in the crucial paper of Bruce Heezen(1960),[44] which would trigger a real revolution in think-ing. A profound consequence of seafloor spreading isthat new crust was, and still is, being continually createdalong the oceanic ridges. Therefore, Heezen advocatedthe so-called "expanding Earth" hypothesis of S. WarrenCarey (see above). So, still the question remained: howcan new crust be continuously added along the oceanicridges without increasing the size of the Earth? In real-ity, this question had been solved already by numerousscientists during the forties and the fifties, like ArthurHolmes, Vening-Meinesz, Coates and many others: Thecrust in excess disappeared along what were called theoceanic trenches, where so-called “subduction” occurred.Therefore, when various scientists during the early sixtiesstarted to reason on the data at their disposal regardingthe ocean floor, the pieces of the theory quickly fell intoplace.The question particularly intrigued Harry HammondHess, a Princeton University geologist and a Naval Re-serve Rear Admiral, and Robert S. Dietz, a scientist withthe U.S. Coast and Geodetic Survey who first coined theterm seafloor spreading. Dietz and Hess (the former pub-lished the same idea one year earlier in Nature,[45] butpriority belongs to Hess who had already distributed anunpublished manuscript of his 1962 article by 1960)[46]were among the small handful who really understoodthe broad implications of sea floor spreading and howit would eventually agree with the, at that time, uncon-ventional and unaccepted ideas of continental drift andthe elegant and mobilistic models proposed by previousworkers like Holmes.In the same year, Robert R. Coats of the U.S. GeologicalSurvey described the main features of island arc subduc-tion in the Aleutian Islands. His paper, though little noted(and even ridiculed) at the time, has since been called“seminal” and “prescient”. In reality, it actually showsthat the work by the European scientists on island arcsand mountain belts performed and published during the1930s up until the 1950s was applied and appreciated alsoin the United States.If the Earth’s crust was expanding along the oceanicridges, Hess and Dietz reasoned like Holmes and othersbefore them, it must be shrinking elsewhere. Hess fol-lowed Heezen, suggesting that new oceanic crust contin-uously spreads away from the ridges in a conveyor belt–like motion. And, using the mobilistic concepts devel-oped before, he correctly concluded that many millionsof years later, the oceanic crust eventually descends alongthe continental margins where oceanic trenches – verydeep, narrow canyons – are formed, e.g. along the rim ofthe Pacific Ocean basin. The important step Hess madewas that convection currents would be the driving force inthis process, arriving at the same conclusions as Holmeshad decades before with the only difference that the thin-ning of the ocean crust was performed using Heezen’smechanism of spreading along the ridges. Hess therefore

concluded that the Atlantic Ocean was expanding whilethe Pacific Ocean was shrinking. As old oceanic crustis “consumed” in the trenches (like Holmes and others,he thought this was done by thickening of the continentallithosphere, not, as now understood, by underthrusting ata larger scale of the oceanic crust itself into the mantle),new magma rises and erupts along the spreading ridgesto form new crust. In effect, the ocean basins are per-petually being “recycled,” with the creation of new crustand the destruction of old oceanic lithosphere occurringsimultaneously. Thus, the new mobilistic concepts neatlyexplained why the Earth does not get bigger with sea floorspreading, why there is so little sediment accumulation onthe ocean floor, and why oceanic rocks are much youngerthan continental rocks.

4.5 Magnetic striping

Normal magneticpolarity

Reversed magnetic polarity

MagmaLitosphere

a

b

c

.

Seafloor magnetic striping.

A demonstration of magnetic striping. (The darker the color is,the closer it is to normal polarity)

For more details on this topic, see Vine–Matthews–Morley hypothesis.

Beginning in the 1950s, scientists like Victor Vacquier,using magnetic instruments (magnetometers) adaptedfrom airborne devices developed during World War II

10 4 DEVELOPMENT OF THE THEORY

to detect submarines, began recognizing odd magneticvariations across the ocean floor. This finding, thoughunexpected, was not entirely surprising because it wasknown that basalt—the iron-rich, volcanic rock makingup the ocean floor—contains a strongly magnetic min-eral (magnetite) and can locally distort compass readings.This distortion was recognized by Icelandic mariners asearly as the late 18th century. More important, be-cause the presence of magnetite gives the basalt measur-able magnetic properties, these newly discovered mag-netic variations provided another means to study the deepocean floor. When newly formed rock cools, such mag-netic materials recorded the Earth’s magnetic field at thetime.As more and more of the seafloor was mapped duringthe 1950s, the magnetic variations turned out not to berandom or isolated occurrences, but instead revealed rec-ognizable patterns. When these magnetic patterns weremapped over a wide region, the ocean floor showed azebra-like pattern: one stripe with normal polarity andthe adjoining stripe with reversed polarity. The overallpattern, defined by these alternating bands of normallyand reversely polarized rock, became known as magneticstriping, and was published by Ron G. Mason and co-workers in 1961, who did not find, though, an explanationfor these data in terms of sea floor spreading, like Vine,Matthews and Morley a few years later.[47]

The discovery of magnetic striping called for an expla-nation. In the early 1960s scientists such as Heezen,Hess and Dietz had begun to theorise that mid-oceanridges mark structurally weak zones where the ocean floorwas being ripped in two lengthwise along the ridge crest(see the previous paragraph). New magma from deepwithin the Earth rises easily through these weak zonesand eventually erupts along the crest of the ridges to cre-ate new oceanic crust. This process, at first denominatedthe “conveyer belt hypothesis” and later called seafloorspreading, operating over many millions of years contin-ues to form new ocean floor all across the 50,000 km-longsystem of mid–ocean ridges.Only four years after the maps with the “zebra pat-tern” of magnetic stripes were published, the link be-tween sea floor spreading and these patterns was correctlyplaced, independently by Lawrence Morley, and by FredVine and Drummond Matthews, in 1963[48] now calledthe Vine-Matthews-Morley hypothesis. This hypothesislinked these patterns to geomagnetic reversals and wassupported by several lines of evidence:[49]

1. the stripes are symmetrical around the crests of themid-ocean ridges; at or near the crest of the ridge,the rocks are very young, and they become progres-sively older away from the ridge crest;

2. the youngest rocks at the ridge crest always havepresent-day (normal) polarity;

3. stripes of rock parallel to the ridge crest alternate

inmagnetic polarity (normal-reversed-normal, etc.),suggesting that they were formed during differentepochs documenting the (already known from inde-pendent studies) normal and reversal episodes of theEarth’s magnetic field.

By explaining both the zebra-like magnetic striping andthe construction of the mid-ocean ridge system, theseafloor spreading hypothesis (SFS) quickly gained con-verts and represented another major advance in the devel-opment of the plate-tectonics theory. Furthermore, theoceanic crust now came to be appreciated as a natural“tape recording” of the history of the geomagnetic fieldreversals (GMFR) of the Earth’s magnetic field. Today,extensive studies are dedicated to the calibration of thenormal-reversal patterns in the oceanic crust on one handand known timescales derived from the dating of basaltlayers in sedimentary sequences (magnetostratigraphy)on the other, to arrive at estimates of past spreading ratesand plate reconstructions.

4.6 Definition and refining of the theory

After all these considerations, Plate Tectonics (or, asit was initially called “New Global Tectonics”) becamequickly accepted in the scientific world, and numerouspapers followed that defined the concepts:

• In 1965, Tuzo Wilson who had been a promotorof the sea floor spreading hypothesis and continen-tal drift from the very beginning[50] added the con-cept of transform faults to themodel, completing theclasses of fault types necessary to make the mobilityof the plates on the globe work out.[51]

• A symposium on continental drift was held at theRoyal Society of London in 1965 which must be re-garded as the official start of the acceptance of platetectonics by the scientific community, and whichabstracts are issued as Blacket, Bullard & Runcorn(1965). In this symposium, Edward Bullard and co-workers showed with a computer calculation howthe continents along both sides of the Atlantic wouldbest fit to close the ocean, which became known asthe famous “Bullard’s Fit”.

• In 1966 Wilson published the paper that referred toprevious plate tectonic reconstructions, introducingthe concept of what is now known as the "WilsonCycle".[52]

• In 1967, at the AmericanGeophysical Union's meet-ing, W. Jason Morgan proposed that the Earth’s sur-face consists of 12 rigid plates that move relative toeach other.[53]

• Two months later, Xavier Le Pichon published acomplete model based on 6 major plates with their

6.3 Formation and break-up of continents 11

relative motions, which marked the final acceptanceby the scientific community of plate tectonics.[54]

• In the same year, McKenzie and Parker indepen-dently presented a model similar to Morgan’s usingtranslations and rotations on a sphere to define theplate motions.[55]

5 Implications for biogeography

Continental drift theory helps biogeographers to explainthe disjunct biogeographic distribution of present day lifefound on different continents but having similar ances-tors.[56] In particular, it explains the Gondwanan distri-bution of ratites and the Antarctic flora.

6 Plate reconstruction

Main article: Plate reconstruction

Reconstruction is used to establish past (and future) plateconfigurations, helping determine the shape and make-up of ancient supercontinents and providing a basis forpaleogeography.

6.1 Defining plate boundaries

Current plate boundaries are defined by theirseismicity.[57] Past plate boundaries within existingplates are identified from a variety of evidence, such asthe presence of ophiolites that are indicative of vanishedoceans.[58]

6.2 Past plate motions

Tectonic motion first began around three billion yearsago.[59]

Various types of quantitative and semi-quantitative infor-mation are available to constrain past plate motions. Thegeometric fit between continents, such as between westAfrica and South America is still an important part ofplate reconstruction. Magnetic stripe patterns provide areliable guide to relative plate motions going back intothe Jurassic period.[60] The tracks of hotspots give abso-lute reconstructions, but these are only available back tothe Cretaceous.[61] Older reconstructions rely mainly onpaleomagnetic pole data, although these only constrainthe latitude and rotation, but not the longitude. Combin-ing poles of different ages in a particular plate to produceapparent polar wander paths provides a method for com-paring the motions of different plates through time.[62]Additional evidence comes from the distribution of cer-tain sedimentary rock types,[63] faunal provinces shown

by particular fossil groups, and the position of orogenicbelts.[61]

6.3 Formation and break-up of continents

The movement of plates has caused the formation andbreak-up of continents over time, including occasionalformation of a supercontinent that contains most or allof the continents. The supercontinent Columbia or Nunaformed during a period of 2,000 to 1,800 million yearsago and broke up about 1,500 to 1,300 million yearsago.[64] The supercontinent Rodinia is thought to haveformed about 1 billion years ago and to have embod-ied most or all of Earth’s continents, and broken up intoeight continents around 600 million years ago. The eightcontinents later re-assembled into another supercontinentcalled Pangaea; Pangaea broke up into Laurasia (whichbecame North America and Eurasia) and Gondwana(which became the remaining continents).The Himalayas, the world’s tallest mountain range, areassumed to have been formed by the collision of two ma-jor plates. Before uplift, they were covered by the TethysOcean.

7 Current plates

Main article: List of tectonic platesDepending on how they are defined, there are usu-

Plate tectonics map

ally seven or eight “major” plates: African, Antarctic,Eurasian, North American, South American, Pacific, andIndo-Australian. The latter is sometimes subdivided intothe Indian and Australian plates.There are dozens of smaller plates, the seven largest ofwhich are the Arabian, Caribbean, Juan de Fuca, Cocos,Nazca, Philippine Sea and Scotia.The current motion of the tectonic plates is today de-termined by remote sensing satellite data sets, calibratedwith ground station measurements.

12 9 SEE ALSO

8 Other celestial bodies (planets,moons)

The appearance of plate tectonics on terrestrial planets isrelated to planetary mass, with more massive planets thanEarth expected to exhibit plate tectonics. Earth may bea borderline case, owing its tectonic activity to abundantwater [65] (silica and water form a deep eutectic.)

8.1 Venus

See also: Geology of Venus

Venus shows no evidence of active plate tectonics. Thereis debatable evidence of active tectonics in the planet’sdistant past; however, events taking place since then (suchas the plausible and generally accepted hypothesis thatthe Venusian lithosphere has thickened greatly over thecourse of several hundred million years) has made con-straining the course of its geologic record difficult. How-ever, the numerous well-preserved impact craters havebeen utilized as a dating method to approximately datethe Venusian surface (since there are thus far no knownsamples of Venusian rock to be dated by more reliablemethods). Dates derived are dominantly in the range 500to 750 million years ago, although ages of up to 1,200million years ago have been calculated. This research hasled to the fairly well accepted hypothesis that Venus hasundergone an essentially complete volcanic resurfacing atleast once in its distant past, with the last event takingplace approximately within the range of estimated sur-face ages. While the mechanism of such an impressivethermal event remains a debated issue in Venusian geo-sciences, some scientists are advocates of processes in-volving plate motion to some extent.One explanation for Venus’ lack of plate tectonics is thaton Venus temperatures are too high for significant wa-ter to be present.[66][67] The Earth’s crust is soaked withwater, and water plays an important role in the develop-ment of shear zones. Plate tectonics requires weak sur-faces in the crust along which crustal slices can move, andit may well be that such weakening never took place onVenus because of the absence of water. However, someresearchers remain convinced that plate tectonics is orwas once active on this planet.

8.2 Mars

See also: Geology of Mars

Mars is considerably smaller than Earth and Venus, andthere is evidence for ice on its surface and in its crust.In the 1990s, it was proposed that Martian Crustal Di-chotomy was created by plate tectonic processes.[68] Sci-

entists today disagree, and believe that it was created ei-ther by upwelling within the Martian mantle that thick-ened the crust of the Southern Highlands and formedTharsis[69] or by a giant impact that excavated theNorthern Lowlands.[70]

Valles Marineris may be a tectonic boundary.[71]

Observations made of the magnetic field of Mars by theMars Global Surveyor spacecraft in 1999 showed patternsof magnetic striping discovered on this planet. Some sci-entists interpreted these as requiring plate tectonic pro-cesses, such as seafloor spreading.[72] However, their datafail a “magnetic reversal test”, which is used to see if theywere formed by flipping polarities of a global magneticfield.[73]

8.3 Galilean satellites of Jupiter

Some of the satellites of Jupiter have features that maybe related to plate-tectonic style deformation, althoughthe materials and specific mechanisms may be differentfrom plate-tectonic activity on Earth. On 8 September2014, NASA reported finding evidence of plate tectonicson Europa, a satellite of Jupiter - the first sign of suchgeological activity on another world other than Earth.[74]

8.4 Titan, moon of Saturn

Titan, the largest moon of Saturn, was reported to showtectonic activity in images taken by the Huygens Probe,which landed on Titan on January 14, 2005.[75]

8.5 Exoplanets

On Earth-sized planets, plate tectonics is more likely ifthere are oceans of water; however, in 2007, two in-dependent teams of researchers came to opposing con-clusions about the likelihood of plate tectonics on largersuper-earths[76][77] with one team saying that plate tecton-ics would be episodic or stagnant[78] and the other teamsaying that plate tectonics is very likely on super-earthseven if the planet is dry.[65]

9 See also• Geological history of Earth• Geosyncline theory• List of plate tectonics topics• Supercontinent cycle• Conservation of angular momentum• List of submarine topographical features• Tectonics

10.1 Notes 13

10 References

10.1 Notes[1] Little, Fowler & Coulson 1990.

[2] Read & Watson 1975.

[3] Scalera & Lavecchia 2006.

[4] Zhen Shao 1997, Hancock, Skinner & Dineley 2000.

[5] Turcotte & Schubert 2002, p. 5.

[6] Turcotte & Schubert 2002.

[7] Turcotte & Schubert 2002, p. 3.

[8] Foulger 2010.

[9] Schmidt & Harbert 1998.

[10] Meissner 2002, p. 100.

[11] “Plate Tectonics: Plate Boundaries”. platetectonics.com.Retrieved 12 June 2010.

[12] “Understanding plate motions”. USGS. Retrieved 12 June2010.

[13] Mendia-Landa, Pedro. “Myths and Legends on NaturalDisasters: Making Sense of OurWorld”. Retrieved 2008-02-05.

[14] van Dijk 1992, van Dijk & Okkes 1991.

[15] Holmes, Arthur (1931). “Radioactivity and Earth Move-ments”. Trans. Geological Society of Glasgow: 559–606.

[16] Tanimoto & Lay 2000.

[17] Smoot et al. 1996.

[18] Spence 1987, White & McKenzie 1989.

[19] Conrad & Lithgow-Bertelloni 2002.

[20] Spence 1987, White & Mckenzie 1989, Segev 2002.

[21] “Alfred Wegener (1880-1930)". University of CaliforniaMuseum of Paleontology.

[22] Neith, Katie (April 15, 2011). “Caltech Researchers UseGPS Data to Model Effects of Tidal Loads on Earth’s Sur-face”. Caltech. Retrieved August 15, 2012.

[23] van Dijk 1992, van Dijk & Okkes 1990).

[24] Moore 1973.

[25] Bostrom 1971.

[26] Scoppola et al. 2006.

[27] Torsvik et al. 2010.

[28] Wegener 1929.

[29] Hughes 2001a.

[30] Wegener 1966, Hughes 2001b.

[31] Runcorn 1956.

[32] Carey 1956.

[33] see for example the milestone paper of Lyman & Fleming1940.

[34] Korgen 1995, Spiess & Kuperman 2003.

[35] Kious & Tilling 1996.

[36] Frankel 1987.

[37] Joly 1909.

[38] Thomson 1863.

[39] Wegener 1912.

[40] Stein & Wysession 2009, p. 26

[41] Carey 1956; see also Quilty 2003.

[42] Holmes 1928; see also Holmes 1978, Frankel 1978.

[43] Lippsett 2001, Lippsett 2006.

[44] Heezen 1960.

[45] Dietz 1961.

[46] Hess 1962.

[47] Mason & Raff 1961, Raff & Mason 1961.

[48] Vine & Matthews 1963.

[49] See summary in Heirzler, Le Pichon & Baron 1966

[50] Wilson 1963.

[51] Wilson 1965.

[52] Wilson 1966.

[53] Morgan 1968.

[54] Le Pichon 1967.

[55] McKenzie & Parker 1967.

[56] Moss & Wilson 1998.

[57] Condie 1997.

[58] Lliboutry 2000.

[59] Kranendonk, V.; Martin, J. (2011). “Onset ofPlate Tectonics”. Science 333 (6041): 413–414.doi:10.1126/science.1208766. PMID 21778389.

[60] Torsvik, Trond Helge. “Reconstruction Methods”. Re-trieved 18 June 2010.

[61] Torsvik 2008.

[62] Butler 1992.

[63] Scotese, C.R. (2002-04-20). “Climate History”. Pale-omap Project. Retrieved 18 June 2010.

[64] Zhao 2002, 2004

[65] Valencia, O'Connell & Sasselov 2007.

14 10 REFERENCES

[66] Kasting 1988.

[67] Bortman, Henry (2004-08-26). “Was Venus alive? “TheSigns are Probably There"". Astrobiology Magazine. Re-trieved 2008-01-08.

[68] Sleep 1994.

[69] Zhong & Zuber 2001.

[70] Andrews-Hanna, Zuber & Banerdt 2008.

[71] Wolpert, Stuart (August 9, 2012). “UCLA scientist dis-covers plate tectonics on Mars”. Yin, An. UCLA. Re-trieved August 13, 2012.

[72] Connerney et al. 1999, Connerney et al. 2005

[73] Harrison 2000.

[74] Dyches, Preston; Brown, Dwayne; Buckley, Michael (8September 2014). “Scientists Find Evidence of 'Diving'Tectonic Plates on Europa”. NASA. Retrieved 8 Septem-ber 2014.

[75] Soderblom et al. 2007.

[76] Convection scaling and subduction on Earth and super-Earths, Diana Valencia, Richard J. O'Connell, Earth andPlanetary Science Letters, Volume 286, Issues 3–4, 15September 2009, Pages 492–502, http://dx.doi.org/10.1016/j.epsl.2009.07.015,

[77] Plate tectonics on super-Earths: Equally or more likelythan on Earth, http://dx.doi.org/10.1016/j.epsl.2011.07.029, Earth and Planetary Science Letters, Volume 310,Issues 3–4, 15 October 2011, Pages 252–261, H.J. vanHeck, P.J. Tackley

[78] GEOPHYSICAL RESEARCH LETTERS, VOL. 34,L19204, 4 PP., 2007, doi:10.1029/2007GL030598,Geological consequences of super-sized Earths, C.O'Neill, A. Lenardic

10.2 Cited books

• Butler, Robert F. (1992). “Applications to paleo-geography”. Paleomagnetism: Magnetic domains togeologic terranes. Blackwell. ISBN 0-86542-070-X. Retrieved 18 June 2010.

• Carey, S.W. (1958). “The tectonic approach to con-tinental drift”. In Carey, S.W. Continental Drift—Asymposium, held in March 1956. Hobart: Univ. ofTasmania. pp. 177–363. Expanding Earth from p.311 to p. 349.

• Condie, K.C. (1997). Plate tectonics and crustal evo-lution (4th ed.). Butterworth-Heinemann. p. 282.ISBN 978-0-7506-3386-4. Retrieved 2010-06-18.

• Foulger, Gillian R. (2010). “Plates vs Plumes: AGeological Controversy.”. Wiley-Blackwell, 364 pp.ISBN 978-1-4051-6148-0.

• Frankel, H. (1987). “The Continental Drift De-bate”. In H.T. Engelhardt Jr and A.L. Caplan.Scientific Controversies: Case Solutions in the reso-lution and closure of disputes in science and tech-nology. Cambridge University Press. ISBN 978-0-521-27560-6.

• Hancock, Paul L.; Skinner, Brian J.; Dineley, DavidL. (2000). The Oxford Companion to The Earth.Oxford University Press. ISBN 0-19-854039-6.

• Hess, H. H. (November 1962). “History of OceanBasins”. In A. E. J. Engel, Harold L. James, and B.F. Leonard. Petrologic studies: a volume to honor ofA. F. Buddington. Boulder, CO: Geological Societyof America. pp. 599–620.

• Holmes, Arthur (1978). Principles of Physical Ge-ology (3 ed.). Wiley. pp. 640–641. ISBN 0-471-07251-6.

• Joly, John (1909). Radioactivity and Geology: AnAccount of the Influence of Radioactive Energy onTerrestrial History. London: Archibald Constable.p. 36. ISBN 1-4021-3577-7.

• Kious, W. Jacquelyne; Tilling, Robert I. (February2001) [1996]. “Historical perspective”. This Dy-namic Earth: the Story of Plate Tectonics (Onlineed.). U.S. Geological Survey. ISBN 0-16-048220-8. Retrieved 2008-01-29. Abraham Ortelius in hiswork Thesaurus Geographicus... suggested that theAmericas were 'torn away from Europe and Africa...by earthquakes and floods... The vestiges of the rup-ture reveal themselves, if someone brings forward amap of the world and considers carefully the coastsof the three [continents].'

• Lippsett, Laurence (2006). “Maurice Ewing and theLamont-Doherty Earth Observatory”. In WilliamTheodore De Bary, Jerry Kisslinger and TomMath-ewson. Living Legacies at Columbia. Columbia Uni-versity Press. pp. 277–297. ISBN 0-231-13884-9.Retrieved 2010-06-22.

• Little, W.; Fowler, H.W.; Coulson, J. (1990).Onions C.T., ed. The Shorter Oxford English Dictio-nary: on historical principles II (3 ed.). ClarendonPress. ISBN 978-0-19-861126-4.

• Lliboutry, L. (2000). Quantitative geophysics andgeology. Springer. p. 480. ISBN 978-1-85233-115-3. Retrieved 2010-06-18.

• McKnight, Tom (2004). Geographica: The com-plete illustrated Atlas of the world. New York:Barnes and Noble Books. ISBN 0-7607-5974-X.*Meissner, Rolf (2002). The Little Book of PlanetEarth. New York: Copernicus Books. p. 202.ISBN 978-0-387-95258-1.

10.3 Cited articles 15

• Moss, S.J.; Wilson, M.E.J. (1998). “Biogeographicimplications from the Tertiary palaeogeographicevolution of Sulawesi and Borneo”. In Hall R, Hol-loway JD (eds). Biogeography and Geological Evo-lution of SE Asia (PDF). Leiden, The Netherlands:Backhuys. pp. 133–163. ISBN 90-73348-97-8.

• Oreskes, Naomi, ed. (2003). Plate Tectonics: AnInsider’s History of the Modern Theory of the Earth.Westview. ISBN 0-8133-4132-9.

• Read, Herbert Harold; Watson, Janet (1975). Intro-duction to Geology. New York: Halsted. pp. 13–15.ISBN 978-0-470-71165-1. OCLC 317775677.

• Schmidt, Victor A.; Harbert, William (1998). “TheLiving Machine: Plate Tectonics”. Planet Earth andthe New Geosciences (3 ed.). p. 442. ISBN 0-7872-4296-9. Retrieved 2008-01-28.

• Schubert, Gerald; Turcotte, Donald L.; Olson, Peter(2001). Mantle Convection in the Earth and Planets.Cambridge: Cambridge University Press. ISBN 0-521-35367-X.

• Smoot, N. Christian; Choi, Dong R.; Meyerhoff,Arthur Augustus; Bhat, Mohammad I.; Morris, A.E. L.; Agocs, W. B.; Kamen-Kaye, M.; Taner, I.(1996). Surge tectonics: a new hypothesis of globalgeodynamics. Solid-State Science and TechnologyLibrary. Springer Netherlands. p. 348. ISBN 978-0-7923-4156-7. |first9= missing |last9= in Authorslist (help)

• Stanley, Steven M. (1999). Earth System History.W.H. Freeman. pp. 211–228. ISBN 0-7167-2882-6.

• Sverdrup, H. U., Johnson, M. W. and Fleming, R.H. (1942). TheOceans: Their physics, chemistry andgeneral biology. Englewood Cliffs: Prentice-Hall. p.1087.

• Thompson, Graham R. and Turk, Jonathan (1991).Modern Physical Geology. Saunders College Pub-lishing. ISBN 0-03-025398-5.

• Torsvik, Trond Helge; Steinberger, Bernhard (De-cember 2006). “Fra kontinentaldrift til manteldy-namikk” [From Continental Drift to Mantle Dy-namics]. Geo (in Norwegian) 8: 20–30. Retrieved22 June 2010., translation: Torsvik, Trond Helge;Steinberger, Bernhard (2008). “From ContinentalDrift to Mantle Dynamics”. In Trond Slagstad andRolv Dahl Gråsteinen. Geology for Society for 150years - The Legacy after Kjerulf 12. Trondheim:Norges Geologiske Undersokelse. pp. 24–38 [Nor-wegian Geological Survey, Popular Science].

• Turcotte, D.L.; Schubert, G. (2002). “Plate Tecton-ics”. Geodynamics (2 ed.). Cambridge UniversityPress. pp. 1–21. ISBN 0-521-66186-2.

• Wegener, Alfred (1929). Die Entstehung der Konti-nente und Ozeane (4 ed.). Braunschweig: FriedrichVieweg & Sohn Akt. Ges. ISBN 3-443-01056-3.

• Wegener, Alfred (1966). The origin of continentsand oceans. Biram John (translator). CourierDover. p. 246. ISBN 0-486-61708-4.

• Winchester, Simon (2003). Krakatoa: The Day theWorld Exploded: August 27, 1883. HarperCollins.ISBN 0-06-621285-5.

• Stein, Seth; Wysession, Michael (2009). An Intro-duction to Seismology, Earthquakes, and Earth Struc-ture. Chichester: John Wiley & Sons. ISBN 978-1-4443-1131-0.

10.3 Cited articles

• Andrews-Hanna, Jeffrey C.; Zuber, MariaT.; Banerdt, W. Bruce (2008). “The Bo-realis basin and the origin of the martiancrustal dichotomy”. Nature 453 (7199):1212–5. Bibcode:2008Natur.453.1212A.doi:10.1038/nature07011. PMID 18580944.

• Blacket, P.M.S.; Bullard, E.; Runcorn, S.K., eds.(1965). A Symposium on Continental Drift, held in28 October 1965. Philosophical Transactions of theRoyal Society A 258 (1088). The Royal Society ofLondon. p. 323.

• Bostrom, R.C. (31 December 1971). “Westwarddisplacement of the lithosphere”. Nature 234(5331): 536–538. Bibcode:1971Natur.234..536B.doi:10.1038/234536a0.

• Connerney, J.E.P.; Acuña, M.H.; Wasilewski,P.J.; Ness, N.F.; Rème H., Mazelle C., Vi-gnes D., Lin R.P., Mitchell D.L., CloutierP.A. (1999). “Magnetic Lineations in the An-cient Crust of Mars”. Science 284 (5415):794–798. Bibcode:1999Sci...284..794C.doi:10.1126/science.284.5415.794. PMID10221909.

• Connerney, J.E.P.; Acuña, M.H.; Ness, N.F.;Kletetschka, G.; Mitchell D.L., Lin R.P.,Rème H. (2005). “Tectonic implications ofMars crustal magnetism”. Proceedings ofthe National Academy of Sciences 102 (42):14970–14975. Bibcode:2005PNAS..10214970C.doi:10.1073/pnas.0507469102. PMC 1250232.PMID 16217034.

• Conrad, Clinton P.; Lithgow-Bertelloni, Car-olina (2002). “How Mantle Slabs DrivePlate Tectonics”. Science 298 (5591):207–9. Bibcode:2002Sci...298..207C.doi:10.1126/science.1074161. PMID 12364804.

16 10 REFERENCES

• Dietz, Robert S. (June 1961). “Continentand Ocean Basin Evolution by Spreadingof the Sea Floor”. Nature 190 (4779):854–857. Bibcode:1961Natur.190..854D.doi:10.1038/190854a0.

• van Dijk, Janpieter; Okkes, F.W. Mark (1990).“The analysis of shear zones in Calabria; implica-tions for the geodynamics of the Central Mediter-ranean”. Rivista Italiana di Paleontologia e Strati-grafia 96 (2–3): 241–270.

• van Dijk, J.P.; Okkes, F.W.M. (1991). “Neogenetectonostratigraphy and kinematics of CalabrianBasins: implications for the geodynamics ofthe Central Mediterranean”. Tectonophysics196: 23–60. Bibcode:1991Tectp.196...23V.doi:10.1016/0040-1951(91)90288-4.

• van Dijk, Janpieter (1992). “Late Neogene fore-arc basin evolution in the Calabrian Arc (CentralMediterranean). Tectonic sequence stratigraphyand dynamic geohistory. With special reference tothe geology of Central Calabria”. Geologica Ultra-jectina 92: 288.

• Frankel, Henry (July 1978). “Arthur Holmesand continental drift”. The British Journalfor the History of Science 11 (2): 130–150.doi:10.1017/S0007087400016551. JSTOR4025726.

• Harrison, C.G.A. (2000). “Questions AboutMagnetic Lineations in the Ancient Crustof Mars”. Science 287 (5453): 547a.doi:10.1126/science.287.5453.547a.

• Heezen, B. (1960). “The rift in the oceanfloor”. Scientific American 203 (4): 98–110.doi:10.1038/scientificamerican1060-98.

• Heirtzler, James R.; Le Pichon, Xavier; Baron,J. Gregory (1966). “Magnetic anomalies overthe Reykjanes Ridge”. Deep Sea Research 13(3): 427–432. Bibcode:1966DSROA..13..427H.doi:10.1016/0011-7471(66)91078-3.

• Holmes, Arthur (1928). “Radioactivity and Earthmovements”. Transactions of the Geological Societyof Glasgow 18: 559–606.

• Hughes, Patrick (8 February 2001). “Alfred We-gener (1880-1930): A Geographic Jigsaw Puzzle”.On the shoulders of giants. Earth Observatory,NASA. Retrieved 2007-12-26. ... on January 6,1912, Wegener... proposed instead a grand visionof drifting continents and widening seas to explainthe evolution of Earth’s geography.

• Hughes, Patrick (8 February 2001). “Alfred We-gener (1880-1930): The origin of continents and

oceans”. On the Shoulders of Giants. Earth Obser-vatory, NASA. Retrieved 2007-12-26. By his thirdedition (1922), Wegener was citing geological evi-dence that some 300 million years ago all the conti-nents had been joined in a supercontinent stretchingfrom pole to pole. He called it Pangaea (all lands),...

• Kasting, James F. (1988). “Runaway and moistgreenhouse atmospheres and the evolution ofEarth and Venus”. Icarus 74 (3): 472–494.Bibcode:1988Icar...74..472K. doi:10.1016/0019-1035(88)90116-9. PMID 11538226.

• Korgen, Ben J. (1995). “A voice from the past:John Lyman and the plate tectonics story” (PDF).Oceanography (The Oceanography Society) 8 (1):19–20. doi:10.5670/oceanog.1995.29.

• Lippsett, Laurence (2001). “Maurice Ewing and theLamont-Doherty Earth Observatory”. Living Lega-cies. Retrieved 2008-03-04.

• Lovett, Richard A (24 January 2006). “Moon IsDragging Continents West, Scientist Says”. Na-tional Geographic News.

• Lyman, J.; Fleming, R.H. (1940). “Composition ofSeawater”. Journal of Marine Research 3: 134–146.

• Mason, Ronald G.; Raff, Arthur D. (1961).“Magnetic survey off the west coast of the UnitedStates between 32°N latitude and 42°N latitude”.Bulletin of the Geological Society of America 72 (8):1259–1266. Bibcode:1961GSAB...72.1259M.doi:10.1130/0016-7606(1961)72[1259:MSOTWC]2.0.CO;2. ISSN0016-7606.

• Mc Kenzie, D.; Parker, R.L. (1967). “TheNorth Pacific: an example of tectonicson a sphere”. Nature 216 (5122): 1276–1280. Bibcode:1967Natur.216.1276M.doi:10.1038/2161276a0.

• Moore, George W. (1973). “WestwardTidal Lag as the Driving Force of PlateTectonics”. Geology 1 (3): 99–100.Bibcode:1973Geo.....1...99M. doi:10.1130/0091-7613(1973)1<99:WTLATD>2.0.CO;2. ISSN0091-7613.

• Morgan, W. Jason (1968). “Rises, Trenches,Great Faults, and Crustal Blocks”. Jour-nal of Geophysical Research 73 (6): 1959–1982. Bibcode:1968JGR....73.1959M.doi:10.1029/JB073i006p01959.

• Le Pichon, Xavier (15 June 1968). “Sea-floor spreading and continental drift”.Journal of Geophysical Research 73 (12):3661–3697. Bibcode:1968JGR....73.3661L.doi:10.1029/JB073i012p03661.

10.3 Cited articles 17

• Quilty, Patrick G.; Banks, Maxwell R. (2003).“Samuel Warren Carey, 1911-2002”. Biographi-cal memoirs. Australian Academy of Science. Re-trieved 2010-06-19. This memoir was originallypublished inHistorical Records of Australian Science(2003) 14 (3).

• Raff, Arthur D.; Mason, Roland G. (1961).“Magnetic survey off the west coast of the UnitedStates between 40°N latitude and 52°N latitude”.Bulletin of the Geological Society of America 72 (8):1267–1270. Bibcode:1961GSAB...72.1267R.doi:10.1130/0016-7606(1961)72[1267:MSOTWC]2.0.CO;2. ISSN0016-7606.

• Runcorn, S.K. (1956). “Paleomagnetic com-parisons between Europe and North America”.Proceedings, Geological Association of Canada 8(1088): 7785. Bibcode:1965RSPTA.258....1R.doi:10.1098/rsta.1965.0016.

• Scalera, G., and Lavecchia, G. (2006). “Frontiersin earth sciences: new ideas and interpretation”. An-nals of Geophysics 49 (1). doi:10.4401/ag-4406 (in-active 2015-01-09).

• Scoppola, B.; Boccaletti, D.; Bevis, M.; Carmi-nati, E.; Doglioni, C. (2006). “The westwarddrift of the lithosphere: A rotational drag?".Geological Society of America Bulletin 118:199–209. Bibcode:2006GSAB..118..199S.doi:10.1130/B25734.1.

• Segev, A (2002). “Flood basalts, continentalbreakup and the dispersal of Gondwana: evidencefor periodic migration of upwelling mantle flows(plumes)". EGU Stephan Mueller Special Publica-tion Series 2: 171–191. doi:10.5194/smsps-2-171-2002. Retrieved 5 August 2010.

• Sleep, Norman H. (1994). “Martian platetectonics”. Journal of Geophysical Research99: 5639. Bibcode:1994JGR....99.5639S.doi:10.1029/94JE00216.

• Soderblom, Laurence A.; Tomasko, Martin G.;Archinal, Brent A.; Becker, Tammy; L. Bushroe,Michael W.; Cook, Debbie A.; Doose, Lyn R.;Galuszka, Donna M.; Hare, Trent M.; Howington-Kraus, Elpitha; Karkoschka, Erich; Kirk, RandolphL.; Lunine, Jonathan I.; McFarlane, Elisabeth A.;Redding, Bonnie L.; Rizk, Bashar; Rosiek, MarkR.; See, Charles; Smith, Peter H. (2007). “To-pography and geomorphology of the Huygens land-ing site on Titan”. Planetary and Space Science 55(13): 2015–2024. Bibcode:2007P&SS...55.2015S.doi:10.1016/j.pss.2007.04.015.

• Spence, William (1987).ref=CITEREFSpence1987 “Slab pull and

the seismotectonics of subducting litho-sphere”. Reviews of Geophysics 25 (1):55–69. Bibcode:1987RvGeo..25...55S.doi:10.1029/RG025i001p00055.

• Spiess, Fred; Kuperman, William (2003). “TheMarine Physical Laboratory at Scripps” (PDF).Oceanography (The Oceanography Society) 16 (3):45–54. doi:10.5670/oceanog.2003.30.

• Tanimoto, Toshiro; Lay, Thorne (7 Novem-ber 2000). “Mantle dynamics and seis-mic tomography”. Proceedings of the Na-tional Academy of Sciences 97 (23): 12409–12410. Bibcode:2000PNAS...9712409T.doi:10.1073/pnas.210382197. PMC 34063.PMID 11035784.

• Thomson, W (1863). “On the secular cooling ofthe earth”. Philosophical Magazine 4 (25): 1–14.doi:10.1080/14786446308643410 (inactive 2015-01-09).

• Torsvik, Trond H.; Steinberger, Bernhard; Gur-nis, Michael; Gaina, Carmen (2010). “Plate tec-tonics and net lithosphere rotation over the past150 My”. Earth and Planetary Science Letters291: 106–112. Bibcode:2010E&PSL.291..106T.doi:10.1016/j.epsl.2009.12.055. Retrieved 18 June2010.

• Valencia, Diana; O'Connell, Richard J.; Sas-selov, Dimitar D (November 2007). “Inevitabil-ity of Plate Tectonics on Super-Earths”. As-trophysical Journal Letters 670 (1): L45–L48.arXiv:0710.0699. Bibcode:2007ApJ...670L..45V.doi:10.1086/524012.

• Vine, F.J.; Matthews, D.H. (1963). “Mag-netic anomalies over oceanic ridges”. Nature 199(4897): 947–949. Bibcode:1963Natur.199..947V.doi:10.1038/199947a0.

• Wegener, Alfred (6 January 1912). “Die Her-ausbildung der Grossformen der Erdrinde (Konti-nente und Ozeane), auf geophysikalischer Grund-lage”. Petermanns Geographische Mitteilungen 63:185–195, 253–256, 305–309.

• White, R.; McKenzie, D. (1989). “Magma-tism at rift zones: The generation of vol-canic continental margins and flood basalts”.Journal of Geophysical Research 94: 7685–7729. Bibcode:1989JGR....94.7685W.doi:10.1029/JB094iB06p07685.

• Wilson, J.T. (8 June 1963). “Hypothesis onthe Earth’s behaviour”. Nature 198 (4884):849–865. Bibcode:1963Natur.198..925T.doi:10.1038/198925a0.

18 11 EXTERNAL LINKS

• Wilson, J. Tuzo (July 1965). “A new class of faultsand their bearing on continental drift”. Nature 207(4995): 343–347. Bibcode:1965Natur.207..343W.doi:10.1038/207343a0.

• Wilson, J. Tuzo (13 August 1966). “Did theAtlantic close and then re-open?". Nature 211(5050): 676–681. Bibcode:1966Natur.211..676W.doi:10.1038/211676a0.

• Zhen Shao, Huang (1997). “Speed of the Continen-tal Plates”. The Physics Factbook.

• Zhao, Guochun, Cawood, Peter A., Wilde, SimonA., and Sun, M. (2002). “Review of global 2.1–1.8 Ga orogens: implications for a pre-Rodinia su-percontinent”. Earth-Science Reviews 59, pp. 125–162. 59: 125. Bibcode:2002ESRv...59..125Z.doi:10.1016/S0012-8252(02)00073-9.

• Zhao, Guochun, Sun, M., Wilde, Simon A., andLi, S.Z. (2004). “A Paleo-Mesoproterozoic su-percontinent: assembly, growth and breakup”.Earth-Science Reviews, 67, pp. 91–123.67: 91. Bibcode:2004ESRv...67...91Z.doi:10.1016/j.earscirev.2004.02.003.

• Zhong, Shijie; Zuber, Maria T. (2001). “Degree-1 mantle convection and the crustal dichotomyon Mars”. Earth and Planetary Science Let-ters 189: 75. Bibcode:2001E&PSL.189...75Z.doi:10.1016/S0012-821X(01)00345-4.

11 External links• This Dynamic Earth: The Story of Plate Tectonics.USGS.

• Understanding Plate Tectonics. USGS.

• The PLATES Project. Jackson School of Geo-sciences.

• An explanation of tectonic forces. Example of cal-culations to show that Earth Rotation could be adriving force.

• Bird, P. (2003); An updated digital model of plateboundaries.

• Map of tectonic plates.

• GPlates, desktop software for the interactive visual-ization of plate-tectonics.

• MORVEL plate velocity estimates and information.C. DeMets, D. Argus, & R. Gordon.

• Google Map of the Topography of Plate Tectonicsthat enables you to zoom in on submarine mid oceanridges, fracture zones, ocean trenches, thermal ventsand submarine volcanoes.

11.1 Videos

• Khan Academy Explanation of evidence

• 750 million years of global tectonic activity. Movie.

19

12 Text and image sources, contributors, and licenses

12.1 Text• Plate tectonics Source: http://en.wikipedia.org/wiki/Plate%20tectonics?oldid=642236177 Contributors: Mav, Bryan Derksen, Tarquin,

Malcolm Farmer, -- April, Youssefsan, William Avery, Roadrunner, Mintguy, Dwheeler, Hephaestos, Stevertigo, Edward, Lir, JohnOwens,Zocky, TMC, Booyabazooka, Dominus, GUllman, Tannin, Wapcaplet, Ixfd64, Cyde, Minesweeper, Ams80, Ahoerstemeier, Stan Shebs,Cferrero, Kingturtle, Julesd, Glenn, Susurrus, Evercat, Lancevortex, Mxn, Raven in Orbit, Pizza Puzzle, Mulad, HolIgor, Emperorbma,Charles Matthews, Vanished user 5zariu3jisj0j4irj, Timwi, Reddi, Dysprosia, Furrykef, Morwen, SEWilco, Samsara, Traroth, Geraki,Raul654, Wetman, Pakaran, David.Monniaux, Pollinator, Slawojarek, Cncs wikipedia, Robbot, Sander123, Moriori, Fredrik, Sappe, Chris73, R3m0t, Kristof vt, WormRunner, Nurg, Naddy, Lowellian, Academic Challenger, Hadal, JesseW, Lupo, Zaui, Dina, David Gerard,Wjbeaty, Stirling Newberry, Jpo, Giftlite, JamesMLane, DocWatson42, Inkling, Lupin, Ferkelparade, Obli, Everyking, Maha ts, Curps,Alison, Home Row Keysplurge, Leonard G., Duncharris, Gilgamesh, Yekrats, Nishka, Mackerm, Avala, Bobblewik, Jrdioko, Andycjp,Quadell, Antandrus, Beland, Phe, Lesgles, Jossi, Vina, OwenBlacker, RetiredUser2, Kevin B12, Mysidia, GeoGreg, Gscshoyru, Dan-Matan, Joyous!, Clemwang, Adashiel, Trevor MacInnis, Mike Rosoft, AliveFreeHappy, DanielCD, EugeneZelenko, Discospinster, Zaheen,Rich Farmbrough, Supercoop, Vsmith, Smyth, Ericamick, Mani1, Martpol, MarkS, Stbalbach, Bender235, Sc147, Zaslav, Neurophyre,Thnr, Kbh3rd, Rascalb, Eric Forste, RJHall, Sockatume, El C, Vanished user kjij32ro9j4tkse, RoyBoy, Bobo192, Circeus, Ersby, Asierra,Wegge, Atomique, Enric Naval, Shenme, Viriditas, Cohesion, Jag123, Vystrix Nexoth, Aquillion, TheProject, Toomuchdespair, Rje, SamKorn, Merope, Conny, Ranveig, Storm Rider, Danski14, Siim, Alansohn, Gary, Enirac Sum, Anthony Appleyard, Richard Harvey, Arthena,Uogl, DiegoMoya, Plumbago, Riana, AzaToth, Lightdarkness, Iris lorain, Mac Davis, Hu, Malo, Avenue, Snowolf, Burwellian, Olegalexan-drov, Rebroad, Knowledge Seeker, M3tainfo, Gpvos, RainbowOfLight, Sciurinæ, Mikeo, Bsadowski1, Computerjoe, SteinbDJ, LukeSurl,Blaxthos, HenryLi, Oleg Alexandrov, Bobrayner, Firsfron, Woohookitty, Miaow Miaow, Kurzon, Pol098, Before My Ken, Jeff3000, Dun-can.france, MONGO, Macaddct1984, Eras-mus, SDC, GalaazV, PeregrineAY, Ashmoo, Graham87, Magister Mathematicae, Porcher,Protargol, Mana Excalibur, Drbogdan, Rjwilmsi, Mayumashu, Jake Wartenberg, Vary, MarSch, Tangotango, Vegaswikian, HappyCam-per, Ligulem, Jasonking, Slac, SeanMack, Ems57fcva, Bubba73, Boccobrock, Brighterorange, Bhadani, Ian Dunster, Williamborg, THEKING, Sango123, Yamamoto Ichiro, Dracontes, Stepanovas, Titoxd, SchuminWeb, RobertG, Musical Linguist, Latka, Nihiltres, AJR,RexNL, Gurch, Simishag, Bks85, Chobot, Skraz, NSR, Gwernol, E Pluribus Anthony, Roboto de Ajvol, The Rambling Man, Wavelength,Borgx, RattusMaximus, NorCalHistory, Ansell, Manop, Gaius Cornelius, CambridgeBayWeather, Chaos, Wimt, NawlinWiki, Madcover-boy, Grafen, Cquan, Długosz, AeonicOmega, Irishguy, Ragesoss, Retired username, Aaron Brenneman, Bobbo, J chaloner, Matticus78,Raven4x4x, Breathstealer, Phaleux, BOT-Superzerocool, DeadEyeArrow, David Underdown, Zzuuzz, Sotakeit, Spondoolicks, Maristod-dard, Pb30, Abune, Xaxafrad, Reyk, Netrapt, Sairjohn, BorgQueen, Petri Krohn, MaNeMeBasat, Scoutersig, Kevin, Anclation, Willtron,Curpsbot-unicodify, Ilmari Karonen, Kungfuadam, Junglecat, Austinbirdman, DVD R W, Bibliomaniac15, Luk, Hughitt1, SmackBot,Kcumming, Lcarsdata, Zazaban, Malkinann, KnowledgeOfSelf, Royalguard11, Kimon, Gnangarra, Pgk, InvictaHOG, Wufpack jack,Bomac, Davewild, Anastrophe, Arny, Hardyplants, Cessator, Kintetsubuffalo, HalfShadow, Srnec, IstvanWolf, Gaff, Gilliam, Hmains,Ppntori, Carl.bunderson, Andy M. Wang, Valley2city, Saros136, Chris the speller, Master Jay, Rajeevmass, Quinsareth, Master of Pup-pets, Tabdulla, George Rodney Maruri Game, Neo-Jay, CSWarren, HubHikari, Whispering, Sbharris, Rlevse, Lightspeedchick, Royboy-crashfan, Suicidalhamster, Zsinj, Xchbla423, Can't sleep, clown will eat me, Ajaxkroon, Tamfang, Kaimiddleton, TheKMan, Rsm99833,Kittybrewster, Edivorce, Pepsidrinka, Aldaron, Krich, Smooth O, Ghiraddje, BesselDekker, Nibuod, Nakon, Rolinator, Zyzzy2, Snapping-Turtle, Professor Chaos, Richard001, ShaunES, Howard the Duck, Andrew c, Mwtoews, DavidJ710, Jitterro, Daniel.Cardenas, DDima,Ck lostsword, Pilotguy, FelisLeo, Kukini, The undertow, ArglebargleIV, Rory096, Harryboyles, Zahid Abdassabur, Sjock, J 1982, Kipala,Popgoes, Sir Nicholas de Mimsy-Porpington, Tktktk, This user has left wikipedia, Bjankuloski06en, RNCoats, PowerCS, IronGargoyle,Shattered, Ben Moore, Ex nihil, Smith609, Andypandy.UK, Korovioff, Muad, Jon186, Shinryuu, Geologyguy, Ryulong, Scottwiki, HogynLleol, Jggouvea, Zapvet, LaMenta3, Eastfrisian, Hgrobe, KJS77, Hu12, Dan Gluck, Iridescent, Michaelbusch, Blondie rox, Joseph Solis inAustralia, Tmangray, Skapur, Newone, Joao.caprivi, Wikiauthor, JSoules, Marysunshine, Civil Engineer III, Eassin, Courcelles, Anger22,Tawkerbot2, Ouishoebean, Chris55, Userdce, Eastlaw, CmdrObot, Ale jrb, Sir Vicious, Van helsing, Agathman, Makeemlighter, Woud-loper, SupaStarGirl, Vampirehelot, MiShogun, CWY2190, DanielRigal, Chmee2, Cindy Jones, Andkore, Basar, Mapletip, Sebastian789,Icek, Cydebot, Abeg92, A876, MC10, Michaelas10, Gogo Dodo, Luckyherb, Ashycool, Ignoramibus, Odie5533, Xndr, B, DumbBOT,Jay32183, Ward3001, SpK, Omicronpersei8, Casliber, FrancoGG, JamesAM, NewInn, Pajz, N5iln, Eco84, Mojo Hand, Young Pioneer,Headbomb, Marek69, West Brom 4ever, John254, E. Ripley, Dfrg.msc, J. W. Love, Grayshi, D.H, Pkeestra, Jman8088, Dawnseeker2000,Elert, Escarbot, Igorwindsor, Dantheman531, Mentifisto, Rickibal, AntiVandalBot, Luna Santin, Turlo Lomon, Masamage, Doc Trop-ics, Jayron32, Jbaranao, Pkm iet, A.M.962, Myanw, Mikenorton, Xigan, JAnDbot, SuperLuigi31, Dan D. Ric, Leuko, Husond, Thebee,MER-C, Hello32020, Awien, Hut 8.5, Howsthatfordamage25, Viriathus, Savant13, Beaumont, Suede, Stardotboy, Magioladitis, Wolf-manSF, EvilPizza, Zakahori, Bongwarrior, VoABot II, Dentren, Hasek is the best, Jespinos, Dedonite, Chris Grose, Phillip Raven, Spar-rowsWing, Avicennasis, KConWiki, §yzergy, David Eppstein, User A1, Cpl Syx, Vssun, TehBrandon, Chris G, DerHexer, Edward321,Esanchez7587, Khalid Mahmood, InvertRect, Migco, RevDan, Patstuart, Bramfab, NatureA16, Gfoulger, Stephenchou0722, Timmy12,MartinBot, Mmoneypenny, Writer777, Poeloq, Aleksander.adamowski, Rettetast, Pagross, R'n'B, CommonsDelinker, AlexiusHoratius,GEOL310, PrestonH, C.R.Selvakumar, J.delanoy, Fred.e, Bogey97, Interplanet Janet, Eliz81, Helon, GeoWriter, Андрей Романенко,SuperMarioGamer, Acalamari, Bot-Schafter, Shawn in Montreal, Smeira, Jameschristopher, SpigotMap, MikeEagling, Raptor24, Tarot-cards, DoubleD17, AntiSpamBot, (jarbarf), Nedhenry, Linuxmatt, BoredTerry, Vanished User 4517, Warut, Srpnor, JHeinonen, Jorfer,Mufka, Iyo8, Njdevilsplayermb, Jcchang05, Cmichael, 2help, Dhaluza, Vanished user 39948282, Treisijs, Redrocket, Num1dgen, Ronbo76,CardinalDan, Spellcast, Xenonice, Wikieditor06, Lights, Sage Connerson, Orphic, Rivazza, Seattle Skier, Chienlit, Irish Pearl, PhilipTrueman, RPlunk2853, Xihuzhaiyue, Charleca, GimmeBot, Cosmic Latte, AlexRampaul, Zamphuor, Katoa, Eve Hall, Tamás Kádár,Miranda, Ann Stouter, Aymatth2, IPSOS, Qxz, Someguy1221, Shindo9Hikaru, DennyColt, Karl07, CanOfWorms, Dlae, Wackowar-rior, Andrewrost3241981, Autodidactyl, Andrew the science guy, RandomXYZb, Caleabbott, Falcon8765, Enviroboy, Proof Pudding,Crazy dude17, GaVaLiTiOuS, Agüeybaná, Brianga, Ceranthor, SLFLdr.Matt, Bobo The Ninja, Gewywewy, AlleborgoBot, Ash2727,NHRHS2010, The Random Editor, Glst2, Kel Ra Met, Ivan Štambuk, PlanetStar, Caulde, Veryfaststuff, Miaowsayscow, Jauerback,Dawn Bard, Caltas, Stephen Marki123, Cwkmail, Triwbe, Lucasbfrbot, LeadSongDog, GrooveDog, Iamthecheekymonkey, Aillema, Tip-toety, Radon210, CombatCraig, Wilson44691, Allmightyduck, Oxymoron83, Geology man, BjörnEF, Robertcurrey, Flyindowndafreeway,Airhogs777, Lightmouse, Poindexter Propellerhead, Techman224, The-G-Unit-Boss, NameThatWorks, Spartan-James, Ward20, Chem-istry geek, Hamiltondaniel, Finetooth, Into The Fray, DaBomb619, Definator, Gubernatoria, Twinsday, ClueBot, Avenged Eightfold, Ar-tichoker, Fyyer, The Thing That Should Not Be, Frederick Miao, EoGuy, Sanja Simat, Shark96z, Mesquishyou101, Drmies, Der Golem,Marzmich, CounterVandalismBot, LizardJr8, TheSmuel, MoNi101, Dreadcenturion, Kansoku, DragonBot, Worthydaydream, Awickert,Excirial, Jusdafax, Designanddraft, Rudolf Pohl, Eeekster, GoRight, Gtstricky, Leonard^Bloom, W3lucario, Sun Creator, Jcdock, Brews

20 12 TEXT AND IMAGE SOURCES, CONTRIBUTORS, AND LICENSES

ohare, Mikaey, Muro Bot, Tseno Maximov, Slayerking94, Erodium, Fastily, Spitfire, Cuptow555, Jovianeye, Applefox, Dthomsen8, Ergo-Sum88, Avoided, NellieBly, JinJian, ZooFari, Dr.mclovin, The “Ninja” Creeper, Eklipse, Reet 3, Addbot, Grayfell, DOI bot, Ronhjones,Pelex, Fluffernutter, Cypkerth, Download, Debresser, Favonian, LinkFA-Bot, Numbo3-bot, Tide rolls, Knowitall4, ,سعی Legobot, Luckas-bot, Yobot, Marcus.aerlous, Maxí, KamikazeBot, Harsha850, Synchronism, AnomieBOT, Andrewrp, Rubinbot, AdjustShift, Goodtimber,Ckruschke, Citation bot, LovesMacs, Xqbot, The sock that should not be, Sellyme, Anna Frodesiak, Scbergman, GrouchoBot, ResidentMario, Mario777Zelda, Omnipaedista, Backpackadam, RibotBOT, Chris.urs-o, Back2reality07, Iceman444k, Doulos Christos, Small-man12q, Shadowjams, Nicholas Sund, Samwb123, Jack B108, BoomerAB, CES1596, GT5162, BSATwinTowers, Dogposter, Tobby72,Ninjaabiosis22, Oldlaptop321, Stvltvs, Togoy, Tranletuhan, Weetoddid, Craig Pemberton, Rost11, Oddfellowslocal151, Scaregenral3,Xhaoz, Stephrox56, DivineAlpha, Applexider, HamburgerRadio, Bigboi256, Decz1, Javert, Amplitude101, XL3000, Pinethicket, Boulaur,Vicenarian, Jonesey95, Jlbsem, Bigcheesy, SpaceFlight89, ShadeofTime09, Heloo guys, Ryswick, FoxBot, TobeBot, Krobin, Trappist themonk, RamblinWreck3, Fama Clamosa, Javierito92, January, Andrewharold, Reaper Eternal, Lauryn-joy, Crustyxspoon, Tbhotch, Min-imac, Kctimes, DARTH SIDIOUS 2, RjwilmsiBot, Powerkeys, Elium2, Androstachys, DASHBot, Aircough, EmausBot, Qurq, Going-Batty, Tommy2010, Wikipelli, ZéroBot, Kenvandellen, Jpvandijk, AManWithNoPlan, Wayne Slam, EricWesBrown, Δ, IGeMiNix, EgoWhite Tray, ChuispastonBot, RockMagnetist, Peter Karlsen, VictorianMutant, Мурад 97, DASHBotAV, Whoop whoop pull up, Kleopa-tra, LM2000, ClueBot NG, Gilderien, Baldy Bill, Foulger, Lanthanum-138, Pragmaticstatistic, Helpful Pixie Bot, Bibcode Bot, JoJaEpp,Wzrd1, Mar2194, Cadiomals, Glevum, Harizotoh9, AlbertBowes, TegetthoffstrasseNr43, Ammorgan2, Asfd666, SreejanAlapati, Dexbot,LightandDark2000, Sidelight12, Josophie, Jwratner1, Marikanessa, Anrnusna, Bkilli1, Monkbot, Trackteur, Jbitz743, I'm your Grandma.,Capacitor12 and Anonymous: 1389

12.2 Images• File:Commons-logo.svg Source: http://upload.wikimedia.org/wikipedia/en/4/4a/Commons-logo.svg License: ? Contributors: ? Originalartist: ?

• File:Earth_Western_Hemisphere.jpg Source: http://upload.wikimedia.org/wikipedia/commons/7/7b/Earth_Western_Hemisphere.jpgLicense: Public domain Contributors: http://visibleearth.nasa.gov/view.php?id=57723 Original artist:

• Reto Stöckli (land surface, shallow water, clouds)• Robert Simmon (enhancements: ocean color, compositing, 3D globes, animation)• Data and technical support: MODIS Land Group; MODIS Science Data Support Team; MODIS Atmosphere Group; MODIS Ocean

Group• Additional data: USGS EROS Data Center (topography); USGS Terrestrial Remote Sensing Flagstaff Field Center (Antarctica);

Defense Meteorological Satellite Program (city lights).• File:Farallon_Plate.jpg Source: http://upload.wikimedia.org/wikipedia/commons/a/a0/Farallon_Plate.jpg License: Public domain Con-tributors: http://svs.gsfc.nasa.gov/vis/a000000/a002400/a002410/ Original artist: NASA

• File:Folder_Hexagonal_Icon.svg Source: http://upload.wikimedia.org/wikipedia/en/4/48/Folder_Hexagonal_Icon.svg License: Cc-by-sa-3.0 Contributors: ? Original artist: ?

• File:Global_plate_motion_2008-04-17.jpg Source: http://upload.wikimedia.org/wikipedia/commons/7/7c/Global_plate_motion_2008-04-17.jpg License: Public domain Contributors: http://sideshow.jpl.nasa.gov/mbh/all/images/global.jpg Original artist: NASA

• File:Grand_Canyon_NP-Arizona-USA.jpg Source: http://upload.wikimedia.org/wikipedia/commons/0/03/Grand_Canyon_NP-Arizona-USA.jpg License: GFDL Contributors: Own work Original artist: Tobias Alt

• File:Oceanic.Stripe.Magnetic.Anomalies.Scheme.svg Source: http://upload.wikimedia.org/wikipedia/commons/7/7e/Oceanic.Stripe.Magnetic.Anomalies.Scheme.svg License: Public domain Contributors: derived from File:Oceanic.Stripe.Magnetic.Anomalies.Scheme.gifOriginal artist: Chmee2

• File:Padlock-silver.svg Source: http://upload.wikimedia.org/wikipedia/commons/f/fc/Padlock-silver.svg License: CC0 Contributors:http://openclipart.org/people/Anonymous/padlock_aj_ashton_01.svg Original artist: This image file was created by AJ Ashton. Uploadedfrom English WP by User:Eleassar. Converted by User:AzaToth to a silver color.

• File:Plate_tectonics_map.gif Source: http://upload.wikimedia.org/wikipedia/commons/b/b4/Plate_tectonics_map.gif License: Publicdomain Contributors: ? Original artist: ?

• File:Plates_tect2_en.svg Source: http://upload.wikimedia.org/wikipedia/commons/8/8a/Plates_tect2_en.svg License: Public domainContributors: http://pubs.usgs.gov/publications/text/slabs.html Original artist: USGS

• File:Polarityshift.gif Source: http://upload.wikimedia.org/wikipedia/commons/2/23/Polarityshift.gif License: Public domain Contribu-tors: Own work Original artist: Powerkeys

• File:Portal-puzzle.svg Source: http://upload.wikimedia.org/wikipedia/en/f/fd/Portal-puzzle.svg License: Public domain Contributors: ?Original artist: ?

• File:Quake_epicenters_1963-98.png Source: http://upload.wikimedia.org/wikipedia/commons/d/db/Quake_epicenters_1963-98.pngLicense: Public domain Contributors: http://denali.gsfc.nasa.gov/dtam/seismic/ Original artist: NASA, DTAM project team

• File:Tectonic_plate_boundaries.png Source: http://upload.wikimedia.org/wikipedia/commons/4/40/Tectonic_plate_boundaries.pngLicense: Public domain Contributors: [1] Original artist: Jose F. Vigil. USGS

• File:Tectonic_plates_boundaries_detailed-en.svg Source: http://upload.wikimedia.org/wikipedia/commons/b/bf/Tectonic_plates_boundaries_detailed-en.svg License: CC BY-SA 2.5 Contributors:

• Background map: Image:Tectonic plates (empty).svg (modified) created by Ævar Arnfjörð Bjarmason under PD and based on an USGSmap Original artist: Eric Gaba (Sting - fr:Sting)

• File:Wallula-Gap-the-sisters.JPG Source: http://upload.wikimedia.org/wikipedia/commons/6/62/Wallula-Gap-the-sisters.JPG Li-cense: CC-BY-SA-3.0 Contributors: ? Original artist: ?

• File:Wegener_Expedition-1930_008.jpg Source: http://upload.wikimedia.org/wikipedia/commons/1/16/Wegener_Expedition-1930_008.jpg License: Public domain Contributors: Archive of Alfred Wegener Institute Original artist: Loewe, Fritz; Georgi, Johannes; Sorge,Ernst; Wegener, Alfred Lothar

12.3 Content license 21

12.3 Content license• Creative Commons Attribution-Share Alike 3.0