document_title: Plate tectonics

question_text: a region of earth’s crust where tectonic plates meet is called a

question_tokens: a region of earth 's crust where tectonic plates meet is called a

text: Plate tectonics

text: Key principles

text: The outer layers of the Earth are divided into the lithosphere and asthenosphere. The division is based on differences in mechanical properties and in the method for the transfer of heat. The lithosphere is cooler and more rigid, while the asthenosphere is hotter and flows more easily. In terms of heat transfer, the lithosphere loses heat by conduction, whereas the asthenosphere also transfers heat by convection and has a nearly adiabatic temperature gradient. This division should not be confused with the chemical subdivision of these same layers into the mantle (comprising both the asthenosphere and the mantle portion of the lithosphere) and the crust: a given piece of mantle may be part of the lithosphere or the asthenosphere at different times depending on its temperature and pressure.

text: The key principle of plate tectonics is that the lithosphere exists as separate and distinct tectonic plates, which ride 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 about 160 mm/year (Nazca Plate; about as fast as hair grows).[4] The driving mechanism behind this movement is described below.

text: Tectonic lithosphere plates consist of lithospheric mantle overlain by one or two types of crustal material: oceanic crust (in older texts called sima from silicon and magnesium) and continental crust (sial from silicon and aluminium). Average oceanic lithosphere is typically 100 km (62 mi) thick;[5] its thickness is a function of its age: as time passes, it conductively cools and subjacent cooling mantle is added to its base. Because it is formed at mid-ocean ridges and spreads outwards, its thickness is therefore a function of its distance from the mid-ocean ridge where it was formed. For a typical distance that oceanic 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 (62 mi) at subduction zones; for shorter or longer distances, the subduction zone (and therefore also the mean) thickness becomes smaller or larger, respectively.[6] Continental lithosphere is typically about 200 km thick, though this varies considerably between basins, mountain ranges, and stable cratonic interiors of continents.

text: The location where two plates meet is called a plate boundary. Plate boundaries are commonly associated with geological events such as earthquakes and the creation of topographic features such as mountains, volcanoes, mid-ocean ridges, and oceanic trenches. The majority of the world's active volcanoes occur along plate boundaries, with the Pacific Plate's Ring of Fire being the most active and widely known today. These boundaries are discussed in further detail below. Some volcanoes occur in the interiors of plates, and these have been variously attributed to internal plate deformation[7] and to mantle plumes.

text: As explained above, tectonic plates may include continental crust or oceanic crust, and most plates contain both. For example, the African Plate includes the continent and parts of the floor of the Atlantic and Indian Oceans. The distinction between oceanic crust and continental 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 and accretion of terranes through tectonic processes, though some of these terranes may contain ophiolite sequences, which are pieces of oceanic crust considered to be part of the continent when they exit the standard cycle of formation and spreading centers and subduction beneath continents. Oceanic crust is also denser than continental crust owing to their different compositions. Oceanic crust is denser because it has less silicon and more heavier elements ("mafic") than continental crust ("felsic").[8] As a result of this density stratification, oceanic crust generally lies below sea level (for example most of the Pacific Plate), while continental crust buoyantly projects above sea level (see the page isostasy for explanation of this principle).

text: Types of plate boundaries

text: Three types of plate boundaries exist,[9] with a fourth, mixed type, characterized by the way the plates move relative to each other. They are associated with different types of surface phenomena. The different types of plate boundaries are:[10][11]

text:
Transform boundaries (Conservative) occur where two lithospheric plates slide, or perhaps more accurately, grind past each other along transform faults, where plates are neither created nor destroyed. The relative motion of the two plates is either sinistral (left side toward the observer) or dextral (right side toward the observer). Transform faults occur across a spreading center. Strong earthquakes can occur along a fault. The San Andreas Fault in California is an example of a transform boundary exhibiting dextral motion.
Divergent boundaries (Constructive) occur where two plates slide apart from each other. At zones of ocean-to-ocean rifting, divergent boundaries form by seafloor spreading, allowing for the formation of new ocean basin. As the ocean plate splits, the ridge forms at the spreading center, the ocean basin expands, and finally, the plate area increases causing many small volcanoes and/or shallow earthquakes. At zones of continent-to-continent rifting, divergent boundaries may cause new ocean basin to form as the continent splits, spreads, the central rift collapses, and ocean fills the basin. Active zones of Mid-ocean ridges (e.g., Mid-Atlantic Ridge and East Pacific Rise), and continent-to-continent rifting (such as Africa's East African Rift and Valley, Red Sea) are examples of divergent boundaries.
Convergent boundaries (Destructive) (or active margins) occur where two plates slide toward each other to form either a subduction zone (one plate moving underneath the other) or a continental collision. At zones of ocean-to-continent subduction (e.g. the Andes mountain range in South America, and the Cascade Mountains in Western United States), the dense oceanic lithosphere plunges beneath the less dense continent. Earthquakes trace the path of the downward-moving plate as it descends into asthenosphere, a trench forms, and as the subducted plate is heated it releases volatiles, mostly water from hydrous minerals, into the surrounding mantle. The addition of water lowers the melting point of the mantle material above the subducting slab, causing it to melt. The magma that results typically leads to volcanism.[12] At zones of ocean-to-ocean subduction (e.g. Aleutian islands, Mariana Islands, and the Japanese island arc), older, cooler, denser crust slips beneath less dense crust. This motion causes earthquakes and a deep trench to form in an arc shape. The upper mantle of the subducted plate then heats and magma rises to form curving chains of volcanic islands. Deep marine trenches are typically associated with subduction zones, and the basins that develop along the active boundary are often called "foreland basins". Closure of ocean basins can occur at continent-to-continent boundaries (e.g., Himalayas and Alps): collision between masses of granitic continental lithosphere; neither mass is subducted; plate edges are compressed, folded, uplifted.
Plate boundary zones occur where the effects of the interactions are unclear, and the boundaries, usually occurring along a broad belt, are not well defined and may show various types of movements in different episodes.

text: Driving forces of plate motion

text: It has generally been accepted that tectonic plates are able to move because of the relative density of oceanic lithosphere and the relative weakness of the asthenosphere. Dissipation of heat from the mantle is acknowledged to be the original source of the energy required to drive plate tectonics through convection or large scale upwelling and doming. The current view, though still a matter of some debate, asserts that as a consequence, a powerful source of plate motion is generated due to the excess density of the oceanic lithosphere sinking in subduction zones. When the new crust forms at mid-ocean ridges, this oceanic lithosphere is initially less dense than the underlying asthenosphere, but it becomes denser with age as it conductively cools and thickens. The greater density of old lithosphere relative to the underlying asthenosphere allows 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 tectonic plates to move easily towards a subduction zone.[13] Although subduction is thought to be the strongest force driving plate motions, it cannot be the only force since there are plates such as the North American Plate which are moving, yet are nowhere being subducted. The same is true for the enormous Eurasian Plate. The sources of plate motion are a matter of intensive research and discussion among scientists. One of the main points is that the kinematic pattern of the movement itself should be separated clearly from the possible geodynamic mechanism that is invoked as the driving force of the observed movement, as some patterns may be explained by more than one mechanism.[14] In short, the driving forces advocated at the moment can be divided into three categories based on the relationship to the movement: mantle dynamics related, gravity related (mostly secondary forces), and earth rotation related.

text: Driving forces related to mantle dynamics

text: For much of the last quarter century, the leading theory of the driving force behind tectonic plate motions envisaged large scale convection currents in the upper mantle, which can be transmitted through the asthenosphere. This theory was launched by Arthur Holmes and some forerunners in the 1930s[15] and was immediately recognized as the solution for the acceptance of the theory as originally discussed in the papers of Alfred Wegener in the early years of the century. However, despite its acceptance, it was long debated in the scientific community because the leading theory still envisaged a static Earth without moving continents up until the major breakthroughs of the early sixties.

text: Two- and three-dimensional imaging of Earth's interior (seismic tomography) shows a varying lateral density distribution throughout the mantle. Such density variations can be material (from rock chemistry), mineral (from variations in mineral structures), or thermal (through thermal expansion and contraction from heat energy). The manifestation of this varying lateral density is mantle convection from buoyancy forces.[16]

text: How mantle convection directly and indirectly relates to plate motion is a matter of ongoing study and discussion in geodynamics. Somehow, this energy must be transferred to the lithosphere for tectonic plates to move. There are essentially two main types of forces that are thought to influence plate motion: friction and gravity.

text:
Basal drag (friction): Plate motion driven by friction between the convection currents in the asthenosphere and the more rigid overlying lithosphere.
Slab suction (gravity): Plate motion driven by local convection currents that exert a downward pull on plates in subduction zones at ocean trenches. Slab suction may occur in a geodynamic setting where basal tractions continue to act on the plate as it dives into the mantle (although perhaps to a greater extent acting on both the under and upper side of the slab).

text: Lately, the convection theory has been much debated, as modern techniques based on 3D seismic tomography still fail to recognize these predicted large scale convection cells; therefore, alternative views have been proposed:

text: In the theory of plume tectonics developed during the 1990s, a modified concept of mantle convection currents is used. It asserts that super plumes rise from the deeper mantle and are the drivers or substitutes of the major convection cells. These ideas, which find their roots in the early 1930s with the so-called "fixistic" ideas of the European and Russian Earth Science Schools, find resonance in the modern theories which envisage hot spots or mantle plumes which remain fixed and are overridden by oceanic and continental lithosphere plates over time and leave their traces in the geological record (though these phenomena are not invoked as real driving mechanisms, but rather as modulators). Modern theories that continue building on the older mantle doming concepts and see plate movements as a secondary phenomena are beyond the scope of this page and are discussed elsewhere (for example on the Plume tectonics page).

text: Another theory is that the mantle flows neither in cells nor large plumes but rather as a series of channels just below the Earth's crust, which then provide basal friction to the lithosphere. This theory, called "surge tectonics", became quite popular in geophysics and geodynamics during the 1980s and 1990s.[17] Recent research, based on three-dimensional computer modeling, suggests that plate geometry is governed by a feedback between mantle convection patterns and the strength of the lithosphere.[18]

text: Driving forces related to gravity

text: Forces related to gravity are usually invoked as secondary phenomena within the framework of a more general driving mechanism such as the various forms of mantle dynamics described above.

text: Gravitational sliding away from a spreading ridge: According to many authors, plate motion is driven by the higher elevation of plates at ocean ridges.[19] As oceanic lithosphere is formed at spreading ridges from hot mantle material, it gradually cools and thickens with age (and thus adds distance from the ridge). Cool oceanic lithosphere is significantly denser than the hot mantle material from which it is derived and so with increasing thickness it gradually subsides into the mantle to compensate the greater load. The result is a slight lateral incline with increased distance from the ridge axis.

text: This force is regarded as a secondary force and is often referred to as "ridge push". This is a misnomer as nothing is "pushing" horizontally and tensional features are dominant along ridges. It is more accurate to refer to this mechanism as gravitational sliding as variable topography across the totality of the plate can vary considerably and the topography of spreading ridges is only the most prominent feature. Other mechanisms generating this gravitational secondary force include flexural bulging of the lithosphere before it dives underneath an adjacent plate which produces a clear topographical feature that can offset, or at least affect, the influence of topographical ocean ridges, and mantle plumes and hot spots, which are postulated to impinge on the underside of tectonic plates.

text: Slab-pull: Current scientific opinion is that the asthenosphere is insufficiently competent or rigid to directly cause motion by friction along the base of the lithosphere. Slab pull is therefore most widely thought to be the greatest force acting on the plates. In this current understanding, plate motion is mostly driven by the weight of cold, dense plates sinking into the mantle at trenches.[20] Recent models indicate that trench suction plays an important role as well. However, the fact that the North American Plate is nowhere being subducted, although it is in motion, presents a problem. The same holds for the African, Eurasian, and Antarctic plates.

text: Gravitational sliding away from mantle doming: According to older theories, one of the driving mechanisms of the plates is the existence of large scale asthenosphere/mantle domes which cause the gravitational sliding of lithosphere plates away from them. This gravitational sliding represents a secondary phenomenon of this basically vertically oriented mechanism. This can act on various scales, from the small scale of one island arc up to the larger scale of an entire ocean basin.[21]

text: Driving forces related to Earth rotation

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text: Alfred Wegener, being a meteorologist, had proposed tidal forces and pole flight force[clarification needed] as the main driving mechanisms behind continental drift; however, these forces were considered far too small to cause continental motion as the concept then[when?] was of continents plowing through oceanic crust.[22] Therefore, Wegener later changed his position and asserted that convection currents are the main driving force of plate tectonics in the last edition of his book in 1929.

text: However, in the plate tectonics context (accepted since the seafloor spreading proposals of Heezen, Hess, Dietz, Morley, Vine, and Matthews (see below) during the early 1960s), the oceanic crust is suggested to be in motion with the continents which caused the proposals related to Earth rotation to be reconsidered. In more recent literature, these driving forces are:

text:
Tidal drag due to the gravitational force the Moon (and the Sun) exerts on the crust of the Earth[23]
Global deformation of the geoid due to small displacements of the rotational pole with respect to the Earth's crust;
Other smaller deformation effects of the crust due to wobbles and spin movements of the Earth rotation on a smaller time scale.

text: Forces that are small and generally negligible are:

text:
The Coriolis force[24][25]
The centrifugal force, which is treated as a slight modification of gravity[24][25]:249

text: For these mechanisms to be overall valid, systematic relationships should exist all over the globe between the orientation and kinematics of deformation and the geographical latitudinal and longitudinal grid of the Earth itself. Ironically, these systematic relations studies in the second half of the nineteenth century and the first half of the twentieth century underline exactly the opposite: that the plates had not moved in time, that the deformation grid was fixed with respect to the Earth equator and axis, and that gravitational driving forces were generally acting vertically and caused only local horizontal movements (the so-called pre-plate tectonic, "fixist theories"). Later studies (discussed below on this page), therefore, invoked many of the relationships recognized during this pre-plate tectonics period to support their theories (see the anticipations and reviews in the work of van Dijk and collaborators).[26]

text: Of the many forces discussed in this paragraph, tidal force is still highly debated and defended as a possible principle driving force of plate tectonics. The other forces are only used in global geodynamic models not using plate tectonics concepts (therefore beyond the discussions treated in this section) or proposed as minor modulations within the overall plate tectonics model.

text: In 1973, George W. Moore[27] of the USGS and R. C. Bostrom[28] presented evidence for a general westward drift of the Earth's lithosphere with respect to the mantle. He concluded that tidal forces (the tidal lag or "friction") caused by the Earth's rotation and the forces acting upon it by the Moon are a driving force for plate tectonics. As the Earth spins eastward beneath the moon, the moon's gravity ever so slightly pulls the Earth's surface layer back westward, just as proposed by Alfred Wegener (see above). In a more recent 2006 study,[29] scientists reviewed and advocated these earlier proposed ideas. It has also been suggested recently in Lovett (2006) that this observation may also explain why Venus and Mars have no plate tectonics, as Venus has no moon and Mars' moons are too small to have significant tidal effects on the planet. In a recent paper,[30] it was suggested that, on the other hand, it can easily be observed that many plates are moving north and eastward, and that the dominantly westward motion of the Pacific Ocean basins derives simply from the eastward bias of the Pacific spreading center (which is not a predicted manifestation of such lunar forces). In the same paper the authors admit, however, that relative to the lower mantle, there is a slight westward component in the motions of all the plates. They demonstrated though that the westward drift, seen only for the past 30 Ma, is attributed to the increased dominance of the steadily growing and accelerating Pacific plate. The debate is still open.

text: Relative significance of each driving force mechanism

text: The vector of a plate's motion is a function of all the forces acting on the plate; however, therein lies the problem regarding the degree to which each process contributes to the overall motion of each tectonic plate.

text: The diversity of geodynamic settings and the properties of each plate result from the impact of the various processes actively driving each individual plate. One method of dealing with this problem is to consider the relative rate at which each plate is moving as well as the evidence related to the significance of each process to the overall driving force on the plate.

text: One of the most significant correlations discovered to date is that lithospheric plates attached to downgoing (subducting) plates move much faster than plates not attached to subducting plates. The Pacific plate, for instance, is essentially surrounded by zones of subduction (the so-called Ring of Fire) and moves much faster than the plates of the Atlantic basin, which are attached (perhaps one could say 'welded') to adjacent continents instead of subducting plates. It is thus thought that forces associated with the downgoing plate (slab pull and slab suction) are the driving forces which determine the motion of plates, except for those plates which are not being subducted.[20] This view however has been contradicted by a recent study which found that the actual motions of the Pacific Plate and other plates associated with the East Pacific Rise do not correlate mainly with either slab pull or slab push, but rather with a mantle convection upwelling whose horizontal spreading along the bases of the various plates drives them along via viscosity-related traction forces.[31] The driving forces of plate motion continue to be active subjects of on-going research within geophysics and tectonophysics.

text: Development of the theory

text: Summary

text: In line with other previous and contemporaneous proposals, in 1912 the meteorologist Alfred Wegener amply described what he called continental drift, expanded in his 1915 book The Origin of Continents and Oceans[32] and the scientific debate started that would end up fifty years later in the theory of plate tectonics.[33] Starting from the idea (also expressed by his forerunners) that the present continents once formed a single land mass (which was called Pangea later on) that drifted apart, thus releasing the continents from the Earth's mantle and likening them to "icebergs" of low density granite floating on a sea of denser basalt.[34] Supporting evidence for the idea came from the dove-tailing outlines of South America's east coast and Africa's west coast, 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.

text: But without detailed evidence and a force sufficient to drive the movement, the theory was not generally accepted: the 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. Distinguished scientists, such as Harold Jeffreys and Charles Schuchert, were outspoken critics of continental drift.

text: 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 currents might have driven the plate movements, and that spreading may have occurred below the sea within the oceanic crust. Concepts close to the elements now incorporated in plate tectonics were proposed by geophysicists and geologists (both fixists and mobilists) like Vening-Meinesz, Holmes, and Umbgrove.

text: 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[clarify],[35] and by Warren Carey in a symposium held in March 1956.[36]

text: 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 floors and the nature of the oceanic crust such as magnetic properties and, more generally, with the development of marine geology[37] which gave evidence for the association of seafloor spreading along the mid-oceanic ridges and magnetic field reversals, published between 1959 and 1963 by Heezen, Dietz, Hess, Mason, Vine & Matthews, and Morley.[38]

text: Simultaneous advances in early seismic imaging techniques in and around Wadati–Benioff zones 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.

text: All this evidence, both from the ocean floor and from the continental margins, made it clear around 1965 that continental drift was feasible and the theory of plate tectonics, which was defined in a series of papers between 1965 and 1967, was born, with all its extraordinary explanatory and predictive power. The theory revolutionized the Earth sciences, explaining a diverse range of geological phenomena and their implications in other studies such as paleogeography and paleobiology.

text: Continental drift

text: In the late 19th and early 20th centuries, geologists assumed that the 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 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.

text: 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.[39]

text: 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.[40]

text: The discovery of radioactivity and its associated heating properties in 1895 prompted a re-examination of the apparent age of the Earth.[41] This had previously been estimated by its cooling rate under the assumption that the Earth's surface radiated like a black body.[42] Those calculations had implied that, even if it started at red heat, the 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 the Earth would be much older, and that its core was still sufficiently hot to be liquid.

text: By 1915, after having published a first article in 1912,[43] Alfred Wegener was making serious arguments for the idea of continental drift in the first edition of The Origin of Continents and Oceans.[32] 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 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 New Brunswick. Furthermore, the Caledonian Mountains of Europe and parts of the Appalachian Mountains of North America are very similar in structure and lithology.

text: 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.

text: Floating continents, paleomagnetism, and seismicity zones

text: 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.

text: 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 Himalayan 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.

text: During the 20th century, improvements in and greater use of seismic instruments such as seismographs 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 the 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)[44] 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.

text: Meanwhile, debates developed around the phenomena 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,[35] 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.

text: This was immediately followed by a symposium in Tasmania in March 1956.[45] In this symposium, the evidence was used in the theory of an expansion of the global crust. In this hypothesis the shifting of the continents can be simply explained by a large increase in size of the Earth since its formation. However, this was unsatisfactory because its supporters could offer no convincing mechanism to produce a significant expansion of the Earth. Certainly there is no evidence that the moon has expanded in the past 3 billion years; other work would soon show that the evidence was equally in support of continental drift on a globe with a stable radius.

text: During the thirties up to the late fifties, works by Vening-Meinesz, Holmes, 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.[46] Often, these contributions are forgotten because:

text:
At the time, continental drift was not accepted.
Some of these ideas were discussed in the context of abandoned fixistic 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.

text: Mid-oceanic ridge spreading and convection

text: 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.[47]

text: 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 Heezen (1960),[48] 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. Therefore, Heezen advocated the so-called "expanding Earth" hypothesis of S. Warren Carey (see above). So, still the question remained: how can new crust be continuously added along the oceanic ridges without increasing the size of the Earth? In reality, this question had been solved already by numerous scientists during the forties and the fifties, 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 sixties started to reason on the data at their disposal regarding the ocean floor, the pieces of the theory quickly fell into place.

text: 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 U.S. Coast and Geodetic Survey who first coined the term seafloor spreading. Dietz and Hess (the former published the same idea one year earlier in Nature,[49] but priority belongs to Hess who had already distributed an unpublished manuscript of his 1962 article by 1960)[50] were among the small handful 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.

text: 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. His paper, though little noted (and even ridiculed) at the time, has since been called "seminal" and "prescient". In reality, it actually 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.

text: If the 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 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 now 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 creation of new crust and the destruction of old oceanic lithosphere occurring simultaneously. Thus, the new mobilistic concepts neatly explained why the 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.

text: Magnetic striping

text: Beginning in the 1950s, scientists like Victor Vacquier, using magnetic instruments (magnetometers) adapted from airborne devices developed during World War II to detect submarines, 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 important, 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 the Earth's magnetic field at the time.

text: 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.[51]

text: 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 the 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 km-long system of mid-ocean ridges.

text: 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 correctly placed, independently by Lawrence Morley, and by Fred Vine and Drummond Matthews, in 1963,[52] now called the Vine-Matthews-Morley hypothesis. This hypothesis linked these patterns to geomagnetic reversals and was supported by several lines of evidence:[53]

text:
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 present-day (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 the Earth's magnetic field.

text: 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 now came to be appreciated as a natural "tape recording" of the history of the geomagnetic field reversals (GMFR) of the Earth's magnetic field. Today, extensive studies are 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.

text: Definition and refining of the theory

text: After all these considerations, Plate Tectonics (or, as it was initially called "New Global Tectonics") became quickly accepted in the scientific world, and numerous papers followed that defined the concepts:

text:
In 1965, Tuzo Wilson who had been a promotor of the sea floor spreading hypothesis and continental drift from the very beginning[54] added the concept of transform faults to the model, completing the classes of fault types necessary to make the mobility of the plates on the globe work out.[55]
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 Blacket, 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 is now known as the "Wilson Cycle".[56]
In 1967, at the American Geophysical Union's meeting, W. Jason Morgan proposed that the Earth's surface consists of 12 rigid plates that move relative to each other.[57]
Two months later, Xavier Le Pichon published a complete model based on 6 major plates with their relative motions, which marked the final acceptance by the scientific community of plate tectonics.[58]
In the same year, McKenzie and Parker independently presented a model similar to Morgan's using translations and rotations on a sphere to define the plate motions.[59]

text: Implications for biogeography

text: Continental drift theory helps biogeographers to explain the disjunct biogeographic distribution of present-day life found on different continents but having similar ancestors.[60] In particular, it explains the Gondwanan distribution of ratites and the Antarctic flora.

text: Plate reconstruction

text: Reconstruction is used to establish past (and future) plate configurations, helping determine the shape and make-up of ancient supercontinents and providing a basis for paleogeography.

text: Defining plate boundaries

text: Current plate boundaries are defined by their seismicity.[61] Past plate boundaries within existing plates are identified from a variety of evidence, such as the presence of ophiolites that are indicative of vanished oceans.[62]

text: Past plate motions

text: Tectonic motion first began around three billion years ago.[63][why?]

text: Various types of quantitative and semi-quantitative information are available to constrain past plate motions. The geometric fit between continents, such as between west Africa and South America is still an important part of plate reconstruction. Magnetic stripe patterns provide a reliable guide to relative plate motions going back into the Jurassic period.[64] The tracks of hotspots give absolute reconstructions, but these are only available back to the Cretaceous.[65] Older reconstructions rely mainly on paleomagnetic pole data, although these only constrain the latitude and rotation, but not the longitude. Combining poles of different ages in a particular plate to produce apparent polar wander paths provides a method for comparing the motions of different plates through time.[66] Additional evidence comes from the distribution of certain sedimentary rock types,[67] faunal provinces shown by particular fossil groups, and the position of orogenic belts.[65]

text: Formation and break-up of continents

text: The movement of plates has caused the formation and break-up of continents over time, including occasional formation of a supercontinent that contains most or all of the continents. The supercontinent Columbia or Nuna formed during a period of 2,000 to 1,800 million years ago and broke up about 1,500 to 1,300 million years ago.[68] The supercontinent Rodinia is thought to have formed about 1 billion years ago and to have embodied most or all of Earth's continents, and broken up into eight continents around 600 million years ago. The eight continents later re-assembled into another supercontinent called Pangaea; Pangaea broke up into Laurasia (which became North America and Eurasia) and Gondwana (which became the remaining continents).

text: The Himalayas, the world's tallest mountain range, are assumed to have been formed by the collision of two major plates. Before uplift, they were covered by the Tethys Ocean.

text: Current plates

text: Depending on how they are defined, there are usually seven or eight "major" plates: African, Antarctic, Eurasian, North American, South American, Pacific, and Indo-Australian. The latter is sometimes subdivided into the Indian and Australian plates.

text: There are dozens of smaller plates, the seven largest of which are the Arabian, Caribbean, Juan de Fuca, Cocos, Nazca, Philippine Sea, and Scotia.

text: The current motion of the tectonic plates is today determined by remote sensing satellite data sets, calibrated with ground station measurements.

text: Other celestial bodies (planets, moons)

text: The appearance of plate tectonics on terrestrial planets is related to planetary mass, with more massive planets than Earth expected to exhibit plate tectonics. Earth may be a borderline case, owing its tectonic activity to abundant water [69] (silica and water form a deep eutectic.)

text: Venus

text: Venus shows no evidence of active plate tectonics. There is debatable evidence of active tectonics in the planet's distant past; however, events taking place since then (such as the plausible and generally accepted hypothesis that the Venusian lithosphere has thickened greatly over the course of several hundred million years) has made constraining the course of its geologic record difficult. However, the numerous well-preserved impact craters have been utilized as a dating method to approximately date the Venusian surface (since there are thus far no known samples of Venusian rock to be dated by more reliable methods). Dates derived are dominantly in the range 500 to 750 million years ago, although ages of up to 1,200 million years ago have been calculated. This research has led to the fairly well accepted hypothesis that Venus has undergone an essentially complete volcanic resurfacing at least once in its distant past, with the last event taking place approximately within the range of estimated surface ages. While the mechanism of such an impressive thermal event remains a debated issue in Venusian geosciences, some scientists are advocates of processes involving plate motion to some extent.

text: One explanation for Venus's lack of plate tectonics is that on Venus temperatures are too high for significant water to be present.[70][71] The Earth's crust is soaked with water, and water plays an important role in the development of shear zones. Plate tectonics requires weak surfaces in the crust along which crustal slices can move, and it may well be that such weakening never took place on Venus because of the absence of water. However, some researchers[who?] remain convinced that plate tectonics is or was once active on this planet.

text: Mars

text: Mars is considerably smaller than Earth and Venus, and there is evidence for ice on its surface and in its crust.

text: In the 1990s, it was proposed that Martian Crustal Dichotomy was created by plate tectonic processes.[72] Scientists today disagree, and think that it was created either by upwelling within the Martian mantle that thickened the crust of the Southern Highlands and formed Tharsis[73] or by a giant impact that excavated the Northern Lowlands.[74]

text: Valles Marineris may be a tectonic boundary.[75]

text: Observations made of the magnetic field of Mars by the Mars Global Surveyor spacecraft in 1999 showed patterns of magnetic striping discovered on this planet. Some scientists interpreted these as requiring plate tectonic processes, such as seafloor spreading.[76] However, their data fail a "magnetic reversal test", which is used to see if they were formed by flipping polarities of a global magnetic field.[77]

text: Icy satellites

text: Some of the satellites of Jupiter have features that may be related to plate-tectonic style deformation, although the materials and specific mechanisms may be different from plate-tectonic activity on Earth. On 8 September 2014, NASA reported finding evidence of plate tectonics on Europa, a satellite of Jupiter—the first sign of subduction activity on another world other than Earth.[78]

text: Titan, the largest moon of Saturn, was reported to show tectonic activity in images taken by the Huygens probe, which landed on Titan on January 14, 2005.[79]

text: Exoplanets

text: On Earth-sized planets, plate tectonics is more likely if there are oceans of water. However, in 2007, two independent teams of researchers came to opposing conclusions about the likelihood of plate tectonics on larger super-Earths[80][81] with one team saying that plate tectonics would be episodic or stagnant[82] and the other team saying that plate tectonics is very likely on super-earths even if the planet is dry.[69]


document_title: Percy Jackson: Sea of Monsters

question_text: who does the voice of the cyclops in percy jackson

root

text: Percy Jackson: Sea of Monsters

text: Plot[edit]

text: While in Camp Half-Blood, Percy recounts the story of Thalia and her sacrifice. A young Annabeth, Luke, Grover and Thalia are running to Camp Half-Blood while being pursued by monsters. Thalia sacrifices herself to get the others into the camp, and her father Zeus transforms her into a pine tree, creating a magical border around the camp. Soon a Cyclops passes through the border and is revealed to be Tyson, Percy's half-brother. The camp is later attacked by a Colchis Bull who breaks through the border and ravages Camp Half-Blood. Percy defeats it with the help of Tyson, Annabeth, and Clarisse. Following this, Luke (who had survived his and Percy's battle in the previous film) appears and confronts Percy, trying to convert him to his cause. When Percy refuses, Luke disappears.

tag: p

text: The campers realize that Thalia's tree has been poisoned by Luke and they are vulnerable to attacks. Percy visits the Oracle, who tells him of a prophecy of a half-blood of the eldest gods either saving or destroying Olympus. Chiron tells Percy that he is the only living, human half-blood of the eldest gods, so the half-blood in the Prophecy may refer to him. Annabeth and Grover learn about the Golden Fleece, which has the power to heal anything, and propose a quest in which they retrieve the Fleece and use it to heal Thalia's tree. Mr. D chooses Clarisse to lead the quest, much to Annabeth's and Percy's dismay. Percy convinces Grover and Annabeth to accompany him on the quest, and Tyson joins them. Annabeth hails the Chariot of Damnation, and Percy threatens the three drivers (the Graeae) to tell him of his prophecy, giving him coordinates for the Sea of Monsters (the Bermuda Triangle) before ejecting the group from the cab in Washington D.C. because they lack money. While walking down the street, Grover is kidnapped by Chris Rodriguez and taken to Luke. Percy, Annabeth, and Tyson first locate Luke with the help of Hermes, then ride a Hippokampos to his yacht, the Andromeda. Luke reveals his plan to revive Kronos using the Fleece so Olympus will be destroyed. Percy and they are then locked in the brig, though they later escape when Percy uses his ability to manipulate water.

text: The group is consumed by Charybdis, and they discover Clarisse in the monster's stomach. Percy and Clarisse work together to escape Charybdis by shooting a hole through its gut, and soon they arrive at Circeland, Polyphemus's lair. Percy finds Grover, and the five escape Polyphemus, retrieving the fleece and trapping him in his cave. Afterwards, Luke arrives and demands the fleece from Percy, who refuses. Luke shoots a crossbow bolt at Percy, but Tyson takes the bolt in the chest and falls into the water below.

text: Luke begins reviving Kronos and Annabeth encourages Percy to take leadership. The team escapes captivity, and Percy grapples with Luke over the Fleece, like the prophecy said they would, but Luke easily gains the upper hand. Luke is suddenly thrown away by Tyson, revealed to have survived his wound due to the water healing it, as he is Poseidon's son. Kronos rises from the sarcophagus and consumes Luke and Grover before battling Percy. Percy realizes that Riptide is the "cursed blade" of the prophecy and slices Kronos into pieces imprisoning Kronos in the sarcophagus once again, causing him to regurgitate Grover and Luke, the latter landing in Polyphemus's Lair. Their victory is short lived as Annabeth is stabbed by the Manticore, who is killed in turn by Clarisse and Grover. Annabeth dies in Percy's arms but is resurrected by the Fleece. Percy then gives the fleece to Clarisse, and they return to Camp Half-Blood. Clarisse places the fleece on Thalia's tree. The group returns the next day to find Thalia alive, as the fleece returned her to human form.

text: Percy realizes that Thalia, as a child of Zeus, is another possible child of the prophecy about either preserving or destroying Olympus. The film ends showing the sarcophagus with Kronos's remains in it glowing, implying that Kronos still has some degree of his power, and is still planning to return.

text: Cast/Characters[edit]

text: Demigods[edit]

text:
Logan Lerman as Percy Jackson, the demigod son of Poseidon.[5]
Alexandra Daddario as Annabeth Chase, the demigod daughter of Athena, and Percy's secret crush.[5]

Alisha Newton portrays the younger Annabeth.

Douglas Smith as Tyson, Percy's Cyclops half-brother.[6]
Leven Rambin as Clarisse La Rue, the demigod daughter of Ares.[7]
Brandon T. Jackson as Grover Underwood, Percy's best friend and keeper, a satyr.[5]

Bjorn Yearwood portrays the younger Grover.

Jake Abel as Luke Castellan, the demigod son of Hermes and the main antagonist.[5]

Samuel Braun portrays the younger Luke.

Paloma Kwiatkowski as Thalia Grace, the demigod daughter of Zeus.[8][9]

Katelyn Mager portrays the younger Thalia.

Grey Damon as Chris Rodriguez, a rogue demigod of unknown parentage who helps Luke to resurrect Kronos.

tag: ul

text: Gods[edit]

text:
Stanley Tucci as Mr. D / Dionysus, the god of wine, celebrations, ecstasy, and theatre and director of Camp Half-Blood.[7]
Nathan Fillion as Hermes, Luke's father; the god of trade, thieves, travelers, sports, athletes, and messenger of the gods of Mount Olympus.[10]

Octavia Spencer as the voice of Martha, a snake that is in Hermes' caduceus.
Craig Robinson as the voice of George, a snake that is in Hermes's caduceus.

Robert Knepper as the voice of Kronos, the King of the Titans, father of Zeus, Poseidon, Hades, Hestia, Demeter, Hera, Chiron, and Luke's master.

text: Other characters[edit]

text:
Anthony Head as Chiron, the activities director at Camp Half Blood. Chiron is a centaur and the immortal son of Kronos and brother of Zeus, Poseidon, Hades, Demeter, Hestia and Hera.[5] Chiron was previously played by Pierce Brosnan in The Lightning Thief.
Robert Maillet as Polyphemus, the Cyclops that is guarding the Golden Fleece.[9]

Ron Perlman as the voice of Polyphemus

Shohreh Aghdashloo as the voice of Oracle of Delphi
Missi Pyle,[9] Yvette Nicole Brown[9] and Mary Birdsong[11] as the Graeae
Jordan Weller as Ichneutae, the acolyte of Clarisse[citation needed]
Derek Mears and Aleks Paunovic as Cyclopes.[12]

text: Production[edit]

text: Reports of a second Percy Jackson film first surfaced in March 2011.[13][14] On October 12, 2011, a sequel was officially confirmed by 20th Century Fox.[15] Filming for Percy Jackson: Sea of Monsters began on April 16, 2012. The film was originally going to be released on March 15, 2013,[16] but in May 2012, the release date was postponed to August 16, 2013.[17] In April 2013, a final release date was set for August 7, 2013.[18] Filming took place in Robert Burnaby Park in Burnaby, B.C.; however from June 20 to July 22, they filmed in New Orleans for Princess Andromeda scenes,[19] including the former site of Six Flags New Orleans.[20] More filming took place in January 2013. On January 22, 2013, Logan Lerman released a statement on Twitter that read "Last day of shooting on Percy Jackson 2" accompanied by a photo of the shooting.[21]

text: Development[edit]

text: In February 2011, it was revealed in the online subscription magazine Production Weekly that the film was in production.[22] In another source, the lead cast members from the first movie were expected to return for their roles. Chris Columbus would not be returning as director, though he would be producing the movie together with Karen Rosenfelt (producer of the Twilight movie Breaking Dawn). Scott Alexander and Larry Karaszewski were hired as the scriptwriters.[23] Marc Guggenheim was hired to re-write the screenplay and Alexander and Karaszewski were uncredited. On June 16, 2011, it was announced that Thor Freudenthal would be directing the movie.[24] Shooting began in summer 2012. On October 12, 2011, it was announced that the film would be released on March 26, 2013. On April 6, it was announced that the movie was pushed up to August 7, 2013.[25] On May 31, 2012, it was announced that the movie had been pushed back to August 16, 2013.[26]

text: Filming[edit]

text: On January 13, 2012, a brand new production list was released and stated that filming would take place between April 26, 2012 and July 11, 2012.[27][28] It was filmed in Vancouver, British Columbia, and New Orleans, Louisiana, with the abandoned Six Flags New Orleans also serving as a filming location . Filming wrapped up in July and then started again in January for reshoots. It wrapped up on January 22, 2013.[29][30]

text: Marketing[edit]

text: Five official stills were released on March 21, 2013.[31] On April 2, the trailer for the film was uploaded on YouTube. A teaser poster was released on April 16. A second trailer was released on May 29, 2013. A third international trailer was released on the June 25, 2013, on YouTube. Since July 19, three TV spots have been released known as "Story", "Cast" and "Family". A clip from the film was released on the internet on July 23, where it was later uploaded onto YouTube. Later many more new clips were released.

text: Smart & Final stores in California, Arizona, and Nevada offered Hollywood Movie Money Certificate good for one free movie ticket with the purchase of two First Street Bakery items as part of the movie promotion.[32]

text: Reception[edit]

text: Critical response[edit]

text: The film received mixed reviews. The review aggregator website Rotten Tomatoes reported a 41% approval rating with an average rating of 5.1/10 based on 111 reviews. The website's consensus reads, "It's pretty and packed with action; unfortunately, Percy Jackson: Sea of Monsters is also waterlogged with characters and plots that can't help but feel derivative."[33] On Metacritic, which assigns a normalized rating out of 100 based on reviews from critics, the film has a score of 39 based on 33 collected reviews, indicating "generally unfavorable reviews".[34]

text: Jim Vejvoda of IGN rated the movie a 6 out of 10: "There are worse sequels than the CG-heavy Percy Jackson: Sea of Monsters, but it's just such overly familiar territory."[35] Gary Goldstein of the Los Angeles Times gave the film a positive review, saying that "tweens and young teens should be sufficiently distracted by the movie's brisk pace and heroic mayhem — if they're not too unnerved by its at times nightmarish imagery".[36] James Rocchi of ScreenCrush wrote that the film "is hardly the stuff of legend, but by keeping the plot straightforward and the storytelling clean, it's an odyssey the intended young audience will be glad to take."[37] Marsha McCreadie on RogerEbert.com rated the film two and a half stars out of four, calling it "a gentler-spirited, less flashy enterprise, though it still presents a natural world that can morph at the whim of a god."[38]

text: Andy Webster of The New York Times commented: "Sea of Monsters is diverting enough — the director, Thor Freudenthal ... is savvy with effects and keeps his young cast on point — but it doesn’t begin to approach the biting adolescent tension of the Harry Potter movies."[39] However, Michael Rechtshaffen of The Hollywood Reporter criticized the film as "lack[ing] the energetic zip of its predecessor,"[40] while Bruce Ingram of Chicago Sun-Times opined that "faithful fans of the novels will be unhappy with the liberties taken with the adaptation like they were with the first film."[41] Connie Ogle of The Miami Herald wrote, "[Are] these characters merely prisoners — much like the audience — of a script so uninspired that it demands their stupidity?"[42] Josh Bell of Las Vegas Weekly lambasted the series as a whole as "a thoroughly second-rate franchise ... with movies like Sea of Monsters, it can probably continue in acceptable mediocrity for years to come".[43]

text: Box office[edit]

text: Percy Jackson: Sea of Monsters grossed an $68,559,554 in North America and $133,688,197 internationally for a worldwide total of $202,247,751.

text: The film grossed $5.4 million on its opening day, taking the number No. 2 spot at the domestic box office.[44] During its extended five-day opening weekend the film debuted at the No. 4 spot and grossed $23,258,113.[45]

text: Accolades[edit]

text:
Year
Award
Category
Recipient(s)
Result
Ref.

2014
Young Artist Award
Best Supporting Young Actress in a Feature Film
Katelyn Mager
Nominated
[46]

2014
Kids' Choice Awards
Favorite Movie Hero: Percy Jackson

Nominated

tag: table

text: Soundtrack[edit]

text:
Percy Jackson: Sea of Monsters

Soundtrack album by Andrew Lockington

Released
August 6, 2013 (2013-08-06)

Genre
Soundtrack

Length
68:54

Label
Sony Classical

Producer
Brian Liesegang

text:
No.
Title
Length

1.
"Thalia's Story"
3:42

2.
"Percy at the Lake"
1:29

3.
"Colchis Bull"
4:08

4.
"The Shield is Gone"
1:31

5.
"The Oracle's Prophecy"
3:08

6.
"Cursed Blade Shall Reap"
1:43

7.
"Wild Taxi Ride"
3:25

8.
"Hermes"
2:34

9.
"Hippocampus"
3:34

10.
"Onboard the Yacht"
1:39

11.
"Wave Conjuring"
6:49

12.
"Sea of Monsters"
2:31

13.
"Belly of the Beast"
3:52

14.
"New Coordinates"
2:13

15.
"Polyphemus"
2:58

16.
"Thank You Brother"
6:01

17.
"Kronos"
5:08

18.
"Annabeth and the Fleece"
2:03

19.
"Resurrection"
3:04

20.
"Percy Jackson: Sea of Monsters – Main Titles"
3:15

21.
"To Feel Alive" (composed by Andrew Lockington & Tiff Randol and performed by IAMEVE)
4:06

text: "My Songs Know What You Did in the Dark (Light Em Up)" by Fall Out Boy and "Cameo Lover" by Kimbra were featured in the movie but are unavailable on the soundtrack.

text: Home media[edit]

text: The film was released on 3D Blu-ray, Blu-ray, and DVD on December 17, 2013. The film was additionally released for Digital HD download on December 3.[47][48]

text: Possible sequel[edit]

text: On March 25, 2014, Lerman said that a sequel to Sea of Monsters would not be made.[49] However, a report of March 31, 2014 stated "Logan Lerman has said Percy Jackson 3 could still go ahead" and that the previous report "was taken out of context".[50] At the 2015 Santa Barbara International Film Festival, Lerman said that while he finds the Percy Jackson films fun to make, he has not heard anything about the production of a third film and expressed concern that he and his co-stars were growing too old for their parts.[51]

text: In December 2017, The Walt Disney Company agreed to a 52.4-billion-dollar deal to acquire 21st Century Fox, including the film rights for Percy Jackson.[52]


document_title: List of Olympic Games host cities

question_text: when is the last time usa hosted olympics

text: List of Olympic Games host cities

text: Olympic Games host cities[edit]

text:
City
Country
Continent
Summer (Olympiad)
Winter
Year
Opening Ceremony
Closing Ceremony

Athens
 Greece
Europe
S005I
—
1896
000000002018-04-06-0000April 6
000000002018-04-15-0000April 15

Paris
 France
Europe
S005II
—
1900
000000002018-05-14-0000May 14
000000002018-10-28-0000October 28

St. Louis[a]
 United States
North America
S005III
—
1904
000000002018-07-01-0000July 1
000000002018-11-23-0000November 23

London[c]
 United Kingdom
Europe
S005IV
—
1908
000000002018-04-27-0000April 27
000000002018-10-31-0000October 31

Stockholm
 Sweden
Europe
S005V
—
1912
000000002018-05-05-0000May 5
000000002018-07-22-0000July 22

Berlin
 Germany
Europe
S006VI
—
1916
Cancelled due to WWI[4]

Antwerp[d]
 Belgium
Europe
S007VII
—
1920
000000002018-04-20-0000April 20
000000002018-09-12-0000September 12[5]

Chamonix
 France
Europe
—
W001I
1924
000000002018-01-25-0000January 25
000000002018-02-04-0000February 4[6]

Paris
 France
Europe
S008VIII
—
000000002018-05-04-0000May 4
000000002018-07-27-0000July 27[7]

St. Moritz
  Switzerland
Europe
—
W002II
1928
000000002018-02-11-0000February 11
000000002018-02-19-0000February 19[8]

Amsterdam
 Netherlands
Europe
S009IX
—
000000002018-05-17-0000May 17
000000002018-08-12-0000August 12[9]

Lake Placid
 United States
North America
—
W003III
1932
000000002018-02-04-0000February 4
000000002018-02-15-0000February 15[10]

Los Angeles
 United States
North America
S010X
—
000000002018-07-30-0000July 30
000000002018-08-14-0000August 14[11]

Garmisch-Partenkirchen
 Nazi Germany
Europe
—
W004IV
1936
000000002018-02-06-0000February 6
000000002018-02-16-0000February 16[12]

Berlin
 Nazi Germany
Europe
S011XI
—
000000002018-08-01-0000August 1
000000002018-08-16-0000August 16[13]

Sapporo
Garmisch-Partenkirchen[e]
 Empire of Japan
 Nazi Germany
Asia
Europe
—
W005aV
1940
Cancelled due to WWII[4]

Tokyo
Helsinki[f]
 Empire of Japan
 Finland
Asia
Europe
S012XII
—

Cortina d'Ampezzo
 Italy
Europe
—
W005bV
1944

London
 United Kingdom
Europe
S013XIII
—

St. Moritz
  Switzerland
Europe
—
W005cV
1948
000000002018-01-30-0000January 30
000000002018-02-08-0000February 8

London
 United Kingdom
Europe
S014XIV
—
000000002018-07-29-0000July 29
000000002018-08-14-0000August 14

Oslo
 Norway
Europe
—
W006VI
1952
000000002018-02-14-0000February 14
000000002018-02-25-0000February 25

Helsinki
 Finland
Europe
S015XV
—
000000002018-07-19-0000July 19
000000002018-08-03-0000August 3

Cortina d'Ampezzo
 Italy
Europe
—
W007VII
1956
000000002018-01-26-0000January 26
000000002018-02-05-0000February 5

Melbourne
Stockholm[g]
 Australia
 Sweden
Oceania
Europe
S016XVI
—
000000002018-11-22-0000November 22
000000002018-06-10-0000June 10
000000002018-12-08-0000December 8
000000002018-06-17-0000June 17

Squaw Valley
 United States
North America
—
W008VIII
1960
000000002018-02-18-0000February 18
000000002018-02-28-0000February 28

Rome
 Italy
Europe
S017XVII
—
000000002018-08-25-0000August 25
000000002018-09-11-0000September 11

Innsbruck
 Austria
Europe
—
W009IX
1964
000000002018-01-29-0000January 29
000000002018-02-09-0000February 9

Tokyo
 Japan
Asia
S018XVIII
—
000000002018-10-10-0000October 10
000000002018-10-24-0000October 24

Grenoble
 France
Europe
—
W010X
1968
000000002018-02-06-0000February 6
000000002018-02-18-0000February 18

Mexico City
 Mexico
North America
S019XIX
—
000000002018-10-12-0000October 12
000000002018-10-27-0000October 27

Sapporo
 Japan
Asia
—
W011XI
1972
000000002018-02-03-0000February 3
000000002018-02-13-0000February 13

Munich
 West Germany
Europe
S020XX
—
000000002018-08-26-0000August 26
000000002018-09-11-0000September 11

Innsbruck
 Austria
Europe
—
W012XII
1976
000000002018-02-04-0000February 4
000000002018-02-15-0000February 15

Montreal
 Canada
North America
S021XXI
—
000000002018-07-17-0000July 17
000000002018-08-01-0000August 1

Lake Placid
 United States
North America
—
W013XIII
1980
000000002018-02-12-0000February 12
000000002018-02-24-0000February 24

Moscow
 Soviet Union
Europe[h]
S022XXII
—
000000002018-07-19-0000July 19
000000002018-08-03-0000August 3

Sarajevo
 Yugoslavia
Europe
—
W014XIV
1984
000000002018-02-07-0000February 7
000000002018-02-19-0000February 19

Los Angeles
 United States
North America
S023XXIII
—
000000002018-07-28-0000July 28
000000002018-08-12-0000August 12

Calgary
 Canada
North America
—
W015XV
1988
000000002018-02-13-0000February 13
000000002018-02-28-0000February 28

Seoul
 South Korea
Asia
S024XXIV
—
000000002018-09-17-0000September 17
000000002018-10-02-0000October 2

Albertville
 France
Europe
—
W016XVI
1992
000000002018-02-08-0000February 8
000000002018-02-23-0000February 23

Barcelona
 Spain
Europe
S025XXV
—
000000002018-07-25-0000July 25
000000002018-08-09-0000August 9

Lillehammer
 Norway
Europe
—
W017XVII
1994
000000002018-02-12-0000February 12
000000002018-02-27-0000February 27

Atlanta
 United States
North America
S026XXVI
—
1996
000000002018-07-19-0000July 19
000000002018-08-04-0000August 4

Nagano
 Japan
Asia
—
W018XVIII
1998
000000002018-02-07-0000February 7
000000002018-02-22-0000February 22

Sydney
 Australia
Oceania
S027XXVII
—
2000
000000002018-09-15-0000September 15
000000002018-10-01-0000October 1

Salt Lake City
 United States
North America
—
W019XIX
2002
000000002018-02-08-0000February 8
000000002018-02-24-0000February 24

Athens
 Greece
Europe
S028XXVIII
—
2004
000000002018-08-13-0000August 13
000000002018-08-29-0000August 29

Torino
 Italy
Europe
—
W020XX
2006
000000002018-02-10-0000February 10
000000002018-02-26-0000February 26

Beijing[i]
 China
Asia
S029XXIX
—
2008
000000002018-08-08-0000August 8
000000002018-08-24-0000August 24

Vancouver
 Canada
North America
—
W021XXI
2010
000000002018-02-12-0000February 12
000000002018-02-28-0000February 28

London
 United Kingdom
Europe
S030XXX
—
2012
000000002018-07-27-0000July 27
000000002018-08-12-0000August 12

Sochi
 Russia
Europe[h]
—
W022XXII
2014
000000002018-02-07-0000February 7
000000002018-02-23-0000February 23

Rio de Janeiro
 Brazil
South America
S031XXXI
—
2016
000000002018-08-05-0000August 5
000000002018-08-21-0000August 21

Pyeongchang
 South Korea
Asia
—
W023XXIII
2018
000000002018-02-09-0000February 9
000000002018-02-25-0000February 25

Tokyo
 Japan
Asia
S032XXXII
—
2020
000000002018-07-24-0000July 24
000000002018-08-09-0000August 9

Beijing
 China
Asia
—
W024XXIV
2022
000000002018-02-04-0000February 4
000000002018-02-20-0000February 20

Paris
 France
Europe
S033XXXIII
—
2024
000000002018-07-26-0000July 26
000000002018-08-11-0000August 11

TBD
TBD

—
W025XXV
2026
(TBD)

Los Angeles
 United States
North America
S034XXXIV
—
2028
000000002018-07-21-0000July 21
000000002018-08-06-0000August 6

TBD
TBD

—
W026XXVI
2030
(TBD)

text: Host cities for multiple Summer and Winter Olympic Games[edit]

text:
List of cities that hosted multiple editions of the Olympic Games

City
Country
Continent
Summer Olympics
Winter Olympics
Total

London
 United Kingdom
Europe
3 (1908, 1948, 2012)
0
3

Paris
 France
Europe
3 (1900, 1924, 2024)
0

Los Angeles
 United States
North America
3 (1932, 1984, 2028)
0

Athens
 Greece
Europe
2 (1896, 2004)
0
2

Tokyo
 Japan
Asia
2 (1964, 2020)
0

Beijing
 China
Asia
1 (2008)
1 (2022)

St. Moritz
  Switzerland
Europe
0
2 (1928, 1948)

Innsbruck
 Austria
Europe
0
2 (1964, 1976)

Lake Placid
 United States
North America
0
2 (1932, 1980)

text: The 1906 Intercalated Games are not officially recognized by the IOC as an official Olympic Games.

text: Number of Olympic Games by country[edit]

text:
List of countries ranked by the number of times they hosted the Olympic Games

Rank
Country
Continent
Summer Olympics
Winter Olympics
Total

1
 United States
North America
5 (1904, 1932, 1984, 1996, 2028)
4 (1932, 1960, 1980, 2002)
9

2
 France
Europe
3 (1900, 1924, 2024)
3 (1924, 1968, 1992)
6

3
 Japan
Asia
2 (1940, 1964, 2020)
2 (1940, 1972, 1998)
4

4
 United Kingdom
Europe
3 (1908, 1944, 1948, 2012)
0
3

 Canada
North America
1 (1976)
2 (1988, 2010)

 Italy
Europe
1 (1960)
2 (1944, 1956, 2006)

 German Empire/ Nazi Germany/ West Germany/ Germany
Europe
2 (1916, 1936, 1972)
1 (1936, 1940)

8
 China
Asia
1 (2008)
1 (2022)
2

 South Korea
Asia
1 (1988)
1 (2018)

 Soviet Union/ Russia
Europe
1 (1980)
1 (2014)

 Greece
Europe
2 (1896, 2004)
0

 Australia
Oceania
2 (1956, 2000)
0

 Norway
Europe
0
2 (1952, 1994)

 Austria
Europe
0
2 (1964, 1976)

  Switzerland
Europe
0
2 (1928, 1940, 1948)

 Sweden
Europe
2 (1912, 1956 (equestrian events only))
0

17
 Brazil
South America
1 (2016)
0
1

 Spain
Europe
1 (1992)
0

 SFR Yugoslavia/ Bosnia and Herzegovina
Europe
0
1 (1984)

 Mexico
North America
1 (1968)
0

 Finland
Europe
1 (1940, 1952)
0

 Netherlands
Europe
1 (1928)
0

 Belgium
Europe
1 (1920)
0

text: Number of Olympic Games by continent[edit]

text:
Rank
Continent
Summer Olympics
Winter Olympics
Total

1
Europe
17 (1896, 1900, 1908, 1912, 1920, 1924, 1928, 1936, 1940, 1944, 1948, 1952, 1960, 1972, 1980, 1992, 2004, 2012, 2024)
14 (1924, 1928, 1936, 1940, 1944, 1948, 1952, 1956, 1964, 1968, 1976, 1984, 1992, 1994, 2006, 2014)
31

2
North America
7 (1904, 1932, 1968, 1976, 1984, 1996, 2028)
6 (1932, 1960, 1980, 1988, 2002, 2010)
13

3
Asia
4 (1940, 1964, 1988, 2008, 2020)
4 (1940, 1972, 1998, 2018, 2022)
8

4
Oceania
2 (1956, 2000)
0
2

5
South America
1 (2016)
0
1

6
Africa
0
0
0

text: Unsuccessful cities[edit]

text: This section does not cite any sources. Please help improve this section by adding citations to reliable sources. Unsourced material may be challenged and removed. (February 2018) (Learn how and when to remove this template message)

text:
Country
City
Bids

 United States
Detroit
7

 Hungary
Budapest
6

 Turkey
Istanbul
5

 Spain
Madrid
4

 Argentina
Buenos Aires
4

  Switzerland
Lausanne
4

 United States
Philadelphia
5

 United States
Chicago
4

 United States
Minneapolis
3

 Cuba
Havana
3

 Belgium
Brussels
3

 Azerbaijan
Baku
2

 Qatar
Doha
2

 Spain
Seville
2

 Yugoslavia
Belgrade
2

 Puerto Rico
San Juan
1

 Australia
Brisbane
1

 Slovakia
Poprad
1

 United States
Boston
1