Editing Plate tectonics (section)

== History of the theory ==
{{Further|Plate Tectonics Revolution}}

=== Summary ===
[[File:Tectonic plates boundaries physical World map Wt 180degE centered-en.svg|thumb|upright=1.35|right|Detailed map showing the tectonic plates with their movement vectors]]
The development of the theory of plate tectonics was the scientific and cultural change which occurred during a period of 50 years of scientific debate. The event of the acceptance itself was a [[paradigm shift]] and can therefore be classified as a scientific revolution,<ref>{{Cite journal |last1=Casadevall |first1=Arturo |last2=Fang |first2=Ferric C. |date=1 March 2016 |title=Revolutionary Science |journal=[[mBio]] |volume=7 |issue=2 |pages=e00158–16 |doi=10.1128/mBio.00158-16 |pmc=4810483 |pmid=26933052}}</ref> now described as the [[Plate Tectonics Revolution]].

Around the start of the twentieth century, various theorists unsuccessfully attempted to explain the many geographical, geological, and biological continuities between continents. In 1912, the meteorologist [[Alfred Wegener]] described what he called continental drift, an idea that culminated fifty years later in the modern theory of plate tectonics.<ref>{{Cite web |last=Hughes |first=Patrick |date=8 February 2001 |title=Alfred Wegener (1880–1930): A Geographic Jigsaw Puzzle |url=http://earthobservatory.nasa.gov/Features/Wegener/wegener_2.php |access-date=2007-12-26 |website=On the Shoulders of Giants |publisher=Earth Observatory, [[NASA]] |quote=... on January 6, 1912, Wegener... proposed instead a grand vision of drifting continents and widening seas to explain the evolution of Earth's geography.}}</ref>

Wegener expanded his theory in his 1915 book ''The Origin of Continents and Oceans''.{{sfn|Wegener|1929}} Starting from the idea (also expressed by his forerunners) that the present continents once formed a single land mass (later called [[Pangaea]]), Wegener suggested that these separated and drifted apart, likening them to "icebergs" of low density [[sial]] floating on a sea of denser [[Sima (geology)|sima]].<ref>{{Cite web |last=Hughes |first=Patrick |date=8 February 2001 |title=Alfred Wegener (1880–1930): The origin of continents and oceans |url=http://earthobservatory.nasa.gov/Features/Wegener/wegener_4.php |access-date=2007-12-26 |website=On the Shoulders of Giants |publisher=Earth Observatory, [[NASA]] |quote=By his third edition (1922), Wegener was citing geological evidence that some 300{{nbsp}}million years ago all the continents had been joined in a supercontinent stretching from pole to pole. He called it Pangaea (all lands),...}}</ref>{{sfn|Wegener|1966}} Supporting evidence for the idea came from the dove-tailing outlines of South America's east coast and Africa's west coast [[Antonio Snider-Pellegrini]] had drawn on his maps, and from the matching of the rock formations along these edges. Confirmation of their previous contiguous nature also came from the fossil plants ''[[Glossopteris]]'' and ''[[Gangamopteris]]'', and the [[therapsid]] or [[mammal-like reptile]] ''[[Lystrosaurus]]'', all widely distributed over South America, Africa, Antarctica, India, and Australia. The evidence for such an erstwhile joining of these continents was patent to field geologists working in the southern hemisphere. The South African [[Alex du Toit]] put together a mass of such information in his 1937 publication ''Our Wandering Continents'', and went further than Wegener in recognising the strong links between the [[Gondwana]] fragments.

Wegener's work was initially not widely accepted, in part due to a lack of detailed evidence but mostly because of the lack of a reasonable physically supported mechanism. Earth might have a solid crust and mantle and a liquid core, but there seemed to be no way that portions of the crust could move around. Many distinguished scientists of the time, such as [[Harold Jeffreys]] and [[Charles Schuchert]], were outspoken critics of continental drift.

Despite much opposition, the view of continental drift gained support and a lively debate started between "drifters" or "mobilists" (proponents of the theory) and "fixists" (opponents). During the 1920s, 1930s and 1940s, the former reached important milestones proposing that [[convection current]]s might have driven the plate movements, and that spreading may have occurred below the sea within the oceanic crust. Concepts close to the elements of plate tectonics were proposed by geophysicists and geologists (both fixists and mobilists) like Vening-Meinesz, Holmes, and Umbgrove. In 1941, [[Otto Ampferer]] described, in his publication "Thoughts on the motion picture of the Atlantic region",<ref>[[Otto Ampferer]]: ''[https://www.zobodat.at/pdf/SBAWW_150_0019-0035.pdf Thoughts on the motion picture of the Atlantic region].'' Sber. österr. Akad. Wiss., math.-naturwiss. KL, 150, 19–35, 6 figs., Vienna 1941.</ref> processes that anticipated [[seafloor spreading]] and [[subduction]].<ref>{{Cite journal |last1=Dullo |first1=Wolf-Christian |last2=Pfaffl |first2=Fritz A. |date=28 March 2019 |title=The theory of undercurrent from the Austrian alpine geologist Otto Ampferer (1875–1947): first conceptual ideas on the way to plate tectonics |url=https://cdnsciencepub.com/doi/full/10.1139/cjes-2018-0157 |journal=[[Canadian Journal of Earth Sciences]] |volume=56 |issue=11 |pages=1095–1100 |bibcode=2019CaJES..56.1095D |doi=10.1139/cjes-2018-0157 |s2cid=135079657}}</ref><ref>Karl Krainer, Christoph Hauser: ''[https://www2.uibk.ac.at/downloads/c715/geoalp_sbd1_07/krainer_hauser.pdf Otto Ampferer (1875-1947): pioneer in geology, mountaineer, collector and draughtsman]''. In: Geo. Alp Sonderband 1, 2007, pp. 94–95.</ref> One of the first pieces of geophysical evidence that was used to support the movement of lithospheric plates came from [[paleomagnetism]]. This is based on the fact that rocks of 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 relative position of the magnetic north pole varies through time. Initially, during the first half of the twentieth century, the latter phenomenon was explained by introducing what was called "polar wander" (see [[apparent polar wander]]) (i.e., it was assumed that the north pole location had been shifting through time). An alternative explanation, though, was that the continents had moved (shifted and rotated) relative to the north pole, and each continent, in fact, shows its own "polar wander path". During the late 1950s, it was successfully shown on two occasions that these data could show the validity of continental drift: by Keith Runcorn in a paper in 1956,{{sfn|Runcorn|1956}} and by Warren Carey in a symposium held in March 1956.{{sfn|Carey|1958}}

The second piece of evidence in support of continental drift came during the late 1950s and early 60s from data on the bathymetry of the deep [[ocean floor]]s and the nature of the oceanic crust such as magnetic properties and, more generally, with the development of [[marine geology]]<ref>see for example the milestone paper of {{Harvnb|Lyman|Fleming|1940}}.</ref> which gave evidence for the association of seafloor spreading along the [[mid-oceanic ridge]]s and [[Geomagnetic reversal|magnetic field reversals]], published between 1959 and 1963 by Heezen, Dietz, Hess, Mason, Vine & Matthews, and Morley.<ref>{{Harvnb|Korgen|1995}}, {{Harvnb|Spiess|Kuperman|2003}}.</ref>

Simultaneous advances in early [[seismic]] imaging techniques in and around [[Wadati–Benioff zone]]s along the trenches bounding many continental margins, together with many other geophysical (e.g., gravimetric) and geological observations, showed how the oceanic crust could disappear into the mantle, providing the mechanism to balance the extension of the ocean basins with shortening along its margins.

All this evidence, both from the ocean floor and from the continental margins, made it clear around 1965 that continental drift was feasible. The theory of plate tectonics was defined in a series of papers between 1965 and 1967. The theory revolutionized the Earth sciences, explaining a diverse range of geological phenomena and their implications in other studies such as [[paleogeography]] and [[paleobiology]].

=== Continental drift ===
{{Further|Continental drift}}
In the late 19th and early 20th centuries, geologists assumed that Earth's major features were fixed, and that most geologic features such as basin development and mountain ranges could be explained by vertical crustal movement, described in what is called the [[geosyncline|geosynclinal theory]]. Generally, this was placed in the context of a contracting planet Earth due to heat loss in the course of a relatively short geological time.
[[File:Wegener Expedition-1912 008.jpg|thumb|Alfred Wegener in Greenland in the winter of 1912–13]]
It was observed as early as 1596 that the opposite [[coasts]] of the Atlantic Ocean—or, more precisely, the edges of the [[continental shelves]]—have similar shapes and seem to have once fitted together.{{sfn|Kious|Tilling|1996}}

Since that time many theories were proposed to explain this apparent complementarity, but the assumption of a solid Earth made these various proposals difficult to accept.{{sfn|Frankel|1987}}

The discovery of [[radioactivity]] and its associated [[exothermic|heating]] properties in 1895 prompted a re-examination of the apparent [[age of Earth]].{{sfn|Joly|1909}} This had previously been estimated by its cooling rate under the assumption that Earth's surface radiated like a [[black body]].{{sfn|Thomson|1863}} Those calculations had implied that, even if it started at [[thermal radiation|red heat]], Earth would have dropped to its present temperature in a few tens of millions of years. Armed with the knowledge of a new heat source, scientists realized that Earth would be much older, and that [[Earth's core|its core]] was still sufficiently hot to be liquid.

By 1915, after having published a first article in 1912,{{sfn|Wegener|1912}} Alfred Wegener was making serious arguments for the idea of continental drift in the first edition of ''The Origin of Continents and Oceans''.{{sfn|Wegener|1929}} In that book (re-issued in four successive editions up to the final one in 1936), he noted how the east coast of [[South America]] and the west 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 Mantovani]] and [[Frank Bursley Taylor]] preceded him just to mention a few), but he was the first to marshal significant [[fossil]] and paleo-topographical and climatological evidence to support this simple observation (and was supported in this by researchers such as [[Alex du Toit]]). Furthermore, when the rock [[stratum|strata]] of the margins of separate continents are very similar it suggests that these rocks were formed in the same way, implying that they were joined initially. For instance, parts of [[Scotland]] and [[Ireland]] contain rocks very similar to those found in [[Newfoundland and Labrador|Newfoundland]] and [[New Brunswick]]. Furthermore, the [[Caledonian Mountains]] of Europe and parts of the [[Appalachian Mountains]] of North America are very similar in [[Structural geology|structure]] and [[lithology]].

However, his ideas were not taken seriously by many geologists, who pointed out that there was no apparent mechanism for continental drift. Specifically, they did not see how continental rock could plow through the much denser rock that makes up oceanic crust. Wegener could not explain the force that drove continental drift, and his vindication did not come until after his death in 1930.<ref>{{Cite web |title=Pioneers of Plate Tectonics |url=https://www.geolsoc.org.uk/Plate-Tectonics/Chap1-Pioneers-of-Plate-Tectonics/Alfred-Wegener |url-status=live |archive-url=https://web.archive.org/web/20180323155937/https://www.geolsoc.org.uk/Plate-Tectonics/Chap1-Pioneers-of-Plate-Tectonics/Alfred-Wegener |archive-date=23 March 2018 |access-date=23 March 2018 |website=[[The Geological Society]]}}</ref>

=== Floating continents, paleomagnetism, and seismicity zones ===
[[File:Quake epicenters 1963-98.png|thumb|upright=1.35|Global earthquake [[epicenter]]s, 1963–1998. Most earthquakes occur in narrow belts that correspond to the locations of lithospheric plate boundaries.]]
[[File:Map of earthquakes in 2016.svg|thumb|upright=1.35|right|Map of earthquakes in 2016]]

As it was observed early that although [[granite]] existed on continents, seafloor seemed to be composed of denser [[basalt]], the prevailing concept during the first half of the twentieth century was that there were two types of crust, named "sial" (continental type crust) and "sima" (oceanic type crust). Furthermore, it was supposed that a static shell of strata was present under the continents. It therefore looked apparent that a layer of basalt (sial) underlies the continental rocks.

However, based on abnormalities in [[plumb line deflection]] by the [[Andes]] in Peru, [[Pierre Bouguer]] had deduced that less-dense mountains must have a downward projection into the denser layer underneath. The concept that mountains had "roots" was confirmed by [[George B. Airy]] a hundred years later, during study of [[Himalaya]]n gravitation, and seismic studies detected corresponding density variations. Therefore, by the mid-1950s, the question remained unresolved as to whether mountain roots were clenched in surrounding basalt or were floating on it like an iceberg.

During the 20th century, improvements in and greater use of seismic instruments such as [[seismograph]]s enabled scientists to learn that earthquakes tend to be concentrated in specific areas, most notably along the [[oceanic trenches]] and spreading ridges. By the late 1920s, seismologists were beginning to identify several prominent earthquake zones parallel to the trenches that typically were inclined 40–60° from the horizontal and extended several hundred kilometers into Earth. These zones later became known as Wadati–Benioff zones, or simply Benioff zones, in honor of the seismologists who first recognized them, [[Kiyoo Wadati]] of Japan and [[Hugo Benioff]] of the United States. The study of global seismicity greatly advanced in the 1960s with the establishment of the Worldwide Standardized Seismograph Network (WWSSN){{sfn|Stein|Wysession|2009|p=26}} to monitor the compliance of the 1963 treaty banning above-ground testing of nuclear weapons. The much improved data from the WWSSN instruments allowed seismologists to map precisely the zones of earthquake concentration worldwide.

Meanwhile, debates developed around the phenomenon of polar wander. Since the early debates of continental drift, scientists had discussed and used evidence that polar drift had occurred because continents seemed to have moved through different climatic zones during the past. Furthermore, paleomagnetic data had shown that the magnetic pole had also shifted during time. Reasoning in an opposite way, the continents might have shifted and rotated, while the pole remained relatively fixed. The first time the evidence of magnetic polar wander was used to support the movements of continents was in a paper by [[Keith Runcorn]] in 1956,{{sfn|Runcorn|1956}} and successive papers by him and his students [[Ted Irving]] (who was actually the first to be convinced of the fact that paleomagnetism supported continental drift) and Ken Creer.

This was immediately followed by a symposium on continental drift in [[Tasmania]] in March 1956 organised by [[Samuel Warren Carey|S. Warren Carey]] who had been one of the supporters and promotors of Continental Drift since the thirties<ref>{{Harvnb|Carey|1958}}; see also {{Harvnb|Quilty|Banks|2003}}.</ref> During this symposium, some of the participants used the evidence in the theory of an [[expanding Earth|expansion of the global crust]], a theory which had been proposed by other workers decades earlier. In this hypothesis, the shifting of the continents is explained by a large increase in the size of Earth since its formation. However, although the theory still has supporters in science, this is generally regarded as unsatisfactory because there is no convincing mechanism to produce a significant expansion of Earth. Other work during the following years would soon show that the evidence was equally in support of continental drift on a globe with a stable radius.

During the 1930s up to the late 1950s, works by [[Felix Andries Vening Meinesz|Vening-Meinesz]], Holmes, [[Johannes Herman Frederik Umbgrove|Umbgrove]], and numerous others outlined concepts that were close or nearly identical to modern plate tectonics theory. In particular, the English geologist [[Arthur Holmes]] proposed in 1920 that plate junctions might lie beneath the [[sea]], and in 1928 that convection currents within the mantle might be the driving force.<ref>{{Harvnb|Holmes|1928}}; see also {{Harvnb|Holmes|1978}}, {{Harvnb|Frankel|1978}}.</ref> Often, these contributions are forgotten because:
* At the time, continental drift was not accepted.
* Some of these ideas were discussed in the context of abandoned fixist ideas of a deforming globe without continental drift or an expanding Earth.
* They were published during an episode of extreme political and economic instability that hampered scientific communication.
* Many were published by European scientists and at first not mentioned or given little credit in the papers on sea floor spreading published by the American researchers in the 1960s.

=== Mid-oceanic ridge spreading and convection ===
{{Further|topic=Mid-ocean ridge|Seafloor spreading}}

In 1947, a team of scientists led by [[Maurice Ewing]] utilizing the [[Woods Hole Oceanographic Institution]]'s research vessel ''Atlantis'' and an array of instruments, confirmed the existence of a rise in the central Atlantic Ocean, and found that the floor of the seabed beneath the layer of sediments consisted of basalt, not the granite which is the main constituent of continents. They also found that the oceanic crust was much thinner than continental crust. All these new findings raised important and intriguing questions.<ref>{{Harvnb|Lippsett|2001}}, {{Harvnb|Lippsett|2006}}.</ref>

The new data that had been collected on the ocean basins also showed particular characteristics regarding the bathymetry. One of the major outcomes of these datasets was that all along the globe, a system of mid-oceanic ridges was detected. An important conclusion was that along this system, new ocean floor was being created, which led to the concept of the "[[Great Global Rift]]". This was described in the crucial paper of [[Bruce C. Heezen|Bruce Heezen]] (1960) based on his work with [[Marie Tharp]],{{sfn|Heezen|1960}} which would trigger a real revolution in thinking. A profound consequence of seafloor spreading is that new crust was, and still is, being continually created along the oceanic ridges. For this reason, Heezen initially advocated the so-called "[[expanding Earth]]" hypothesis of S. Warren Carey (see above). Therefore, the question remained as to how new crust could continuously be added along the oceanic ridges without increasing the size of Earth. In reality, this question had been solved already by numerous scientists during the 1940s and the 1950s, like Arthur Holmes, Vening-Meinesz, Coates and many others: The crust in excess disappeared along what were called the oceanic trenches, where so-called "subduction" occurred. Therefore, when various scientists during the early 1960s started to reason on the data at their disposal regarding the ocean floor, the pieces of the theory quickly fell into place.

The question particularly intrigued [[Harry Hammond Hess]], a [[Princeton University]] geologist and a Naval Reserve Rear Admiral, and [[Robert S. Dietz]], a scientist with the [[United States Coast and Geodetic Survey]] who coined the term ''seafloor spreading''. Dietz and Hess (the former published the same idea one year earlier in ''[[Nature (journal)|Nature]]'',{{sfn|Dietz|1961}} but priority belongs to Hess who had already distributed an unpublished manuscript of his 1962 article by 1960){{sfn|Hess|1962}} were among the small number who really understood the broad implications of sea floor spreading and how it would eventually agree with the, at that time, unconventional and unaccepted ideas of continental drift and the elegant and mobilistic models proposed by previous workers like Holmes.

In the same year, [[Robert R. Coats]] of the U.S. Geological Survey described the main features of [[island arc]] subduction in the [[Aleutian Islands]].{{sfn|Coates|1962}} His paper, though little noted (and sometimes even ridiculed) at the time, has since been called "seminal" and "prescient". In reality, it shows that the work by the European scientists on island arcs and mountain belts performed and published during the 1930s up until the 1950s was applied and appreciated also in the United States.

If Earth's crust was expanding along the oceanic ridges, Hess and Dietz reasoned like Holmes and others before them, it must be shrinking elsewhere. Hess followed Heezen, suggesting that new oceanic crust continuously spreads away from the ridges in a conveyor belt–like motion. And, using the mobilistic concepts developed before, he correctly concluded that many millions of years later, the oceanic crust eventually descends along the continental margins where oceanic trenches—very deep, narrow canyons—are formed, e.g. along [[Pacific Ring of Fire|the rim of the Pacific Ocean basin]]. The important step Hess made was that convection currents would be the driving force in this process, arriving at the same conclusions as Holmes had decades before with the only difference that the thinning of the ocean crust was performed using Heezen's mechanism of spreading along the ridges. Hess therefore concluded that the Atlantic Ocean was expanding while the [[Pacific Ocean]] was shrinking. As old oceanic crust is "consumed" in the trenches (like Holmes and others, he thought this was done by thickening of the continental lithosphere, not, as later understood, by underthrusting at a larger scale of the oceanic crust itself into the mantle), new magma rises and erupts along the spreading ridges to form new crust. In effect, the ocean basins are perpetually being "recycled", with the forming of new crust and the destruction of old oceanic lithosphere occurring simultaneously. Thus, the new mobilistic concepts neatly explained why Earth does not get bigger with sea floor spreading, why there is so little sediment accumulation on the ocean floor, and why oceanic rocks are much younger than continental rocks.

=== Magnetic striping ===
[[File:Oceanic.Stripe.Magnetic.Anomalies.Scheme.svg|thumb|Seafloor magnetic striping]]
[[File:Polarityshift.gif|thumb|A demonstration of magnetic striping. The darker the color is, the closer it is to normal polarity.]]
{{Further|Vine–Matthews–Morley hypothesis}}

Beginning in the 1950s, scientists like [[Victor Vacquier]], using magnetic instruments ([[magnetometer]]s) adapted from airborne devices developed during [[World War II]] to detect [[submarine]]s, began recognizing odd magnetic variations across the ocean floor. This finding, though unexpected, was not entirely surprising because it was known that [[basalt]]—the iron-rich, volcanic rock making up the ocean floor—contains a strongly magnetic mineral ([[magnetite]]) and can locally distort compass readings. This distortion was recognized by Icelandic mariners as early as the late 18th century. More importantly, because the presence of magnetite gives the basalt measurable magnetic properties, these newly discovered magnetic variations provided another means to study the deep ocean floor. When newly formed rock cools, such magnetic materials recorded [[Earth's magnetic field]] at the time.

As more and more of the seafloor was mapped during the 1950s, the magnetic variations turned out not to be random or isolated occurrences, but instead revealed recognizable patterns. When these magnetic patterns were mapped over a wide region, the ocean floor showed a [[zebra]]-like pattern: one stripe with normal polarity and the adjoining stripe with reversed polarity. The overall pattern, defined by these alternating bands of normally and reversely polarized rock, became known as magnetic striping, and was published by [[Ron G. Mason]] and co-workers in 1961, who did not find, though, an explanation for these data in terms of sea floor spreading, like Vine, Matthews and Morley a few years later.<ref>{{Harvnb|Mason|Raff|1961}}, {{Harvnb|Raff|Mason|1961}}.</ref>

The discovery of magnetic striping called for an explanation. In the early 1960s scientists such as Heezen, Hess and Dietz had begun to theorise that mid-ocean ridges mark structurally weak zones where the ocean floor was being ripped in two lengthwise along the ridge crest (see the previous paragraph). New [[magma]] from deep within Earth rises easily through these weak zones and eventually erupts along the crest of the ridges to create new oceanic crust. This process, at first denominated the "conveyer belt hypothesis" and later called seafloor spreading, operating over many millions of years continues to form new ocean floor all across the 50,000&nbsp;km-long system of mid-ocean ridges.

Only four years after the maps with the "zebra pattern" of magnetic stripes were published, the link between sea floor spreading and these patterns was recognized independently by [[Lawrence Morley]], and by [[Fred Vine]] and [[Drummond Matthews]], in 1963,{{sfn|Vine|Matthews|1963}} (the [[Vine–Matthews–Morley hypothesis]]). This hypothesis linked these patterns to geomagnetic reversals and was supported by several lines of evidence:<ref>See summary in {{Harvnb|Heirtzler|Le Pichon|Baron|1966}}</ref>
# the stripes are symmetrical around the crests of the mid-ocean ridges; at or near the crest of the ridge, the rocks are very young, and they become progressively older away from the ridge crest;
# the youngest rocks at the ridge crest always have modern (normal) polarity;
# stripes of rock parallel to the ridge crest alternate in magnetic polarity (normal-reversed-normal, etc.), suggesting that they were formed during different epochs documenting the (already known from independent studies) normal and reversal episodes of Earth's magnetic field.

By explaining both the zebra-like magnetic striping and the construction of the mid-ocean ridge system, the seafloor spreading hypothesis (SFS) quickly gained converts and represented another major advance in the development of the plate-tectonics theory. Furthermore, the oceanic crust came to be appreciated as a natural "tape recording" of the history of the geomagnetic field reversals (GMFR) of Earth's magnetic field. Extensive studies were dedicated to the calibration of the normal-reversal patterns in the oceanic crust on one hand and known timescales derived from the dating of basalt layers in sedimentary sequences ([[magnetostratigraphy]]) on the other, to arrive at estimates of past spreading rates and plate reconstructions.

=== Definition and refining of the theory ===
After all these considerations, plate tectonics (or, as it was initially called "New Global Tectonics") became quickly accepted and numerous papers followed that defined the concepts:

* In 1965, [[Tuzo Wilson]] who had been a promoter of the sea floor spreading hypothesis and continental drift from the very beginning{{sfn|Wilson|1963}} added the concept of [[transform fault]]s to the model, completing the classes of fault types necessary to make the mobility of the plates on the globe work out.{{sfn|Wilson|1965}}
* A symposium on continental drift was held at the Royal Society of London in 1965 which must be regarded as the official start of the acceptance of plate tectonics by the scientific community, and which abstracts are issued as {{Harvtxt|Blackett|Bullard|Runcorn|1965}}. In this symposium, [[Edward Bullard]] and co-workers showed with a computer calculation how the continents along both sides of the Atlantic would best fit to close the ocean, which became known as the famous "Bullard's Fit".
* In 1966 Wilson published the paper that referred to previous plate tectonic reconstructions, introducing the concept of what became known as the "[[Wilson Cycle]]".{{sfn|Wilson|1966}}
* In 1967, at the [[American Geophysical Union]]'s meeting, [[W. Jason Morgan]] proposed that Earth's surface consists of 12 rigid plates that move relative to each other.{{sfn|Morgan|1968}}
* Two months later, [[Xavier Le Pichon]] published a complete model based on six major plates with their relative motions, which marked the final acceptance by the scientific community of plate tectonics.{{sfn|Le Pichon|1968}}
* In the same year, [[Dan McKenzie (geophysicist)|McKenzie]] and [[Robert Ladislav Parker|Parker]] independently presented a model similar to Morgan's using translations and rotations on a sphere to define the plate motions.{{sfn|McKenzie|Parker|1967}}
* From that moment onwards, discussions have been focusing on the relative role of the forces driving plate tectonics, in order to evolve from a kinematic concept into a dynamic theory.<ref>Tharp M (1982) Mapping the ocean floor—1947 to 1977. In: The ocean floor: Bruce Heezen commemorative volume, pp. 19–31. New York: Wiley.</ref> Initially these concepts were focused on mantle convection, in the footsteps of A. Holmes, and also introduced the importance of the gravitational pull of subducted slabs through the works of Elsasser, Solomon, Sleep, Uyeda and Turcotte. Other authors evoked external driving forces due to the tidal drag of the Moon and other celestial bodies, and, especially since 2000, with the emergence of computational models reproducing Earth's mantle behaviour to first order,<ref>{{Cite journal |last1=Coltice |first1=Nicolas |last2=Gérault |first2=Mélanie |last3=Ulvrová |first3=Martina |date=2017 |title=A mantle convection perspective on global tectonics |journal=Earth-Science Reviews |volume=165 |pages=120–150 |bibcode=2017ESRv..165..120C |doi=10.1016/j.earscirev.2016.11.006}}</ref><ref>{{Cite journal |last=Bercovici |first=David |date=2003 |title=The generation of plate tectonics from mantle convection |journal=Earth and Planetary Science Letters |volume=205 |issue=3–4 |pages=107–121 |bibcode=2003E&PSL.205..107B |doi=10.1016/S0012-821X(02)01009-9}}</ref> following upon the older unifying concepts of van Bemmelen, authors re-evaluated the important role of mantle dynamics.<ref>{{Cite journal |last1=Crameri |first1=Fabio |last2=Conrad |first2=Clinton P. |last3=Montési |first3=Laurent |last4=Lithgow-Bertelloni |first4=Carolina R. |date=2019 |title=The dynamic life of an oceanic plate |journal=Tectonophysics |volume=760 |pages=107–135 |bibcode=2019Tectp.760..107C |doi=10.1016/j.tecto.2018.03.016|hdl=10852/72186 |hdl-access=free }}</ref>