What are the structural changes due to plate tectonics?

Question

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Answer 1

Plate tectonics cause different features depending where you are.  In the case of a convergent plate boundary with two continental plates you should see the growth of mountain ranges, such as the Himalayas.  However, if it is a subduction zone, around the plate boundary you can expect to see plate loading amounting to something around a meter, but further inland there can very well be a volcanic mountain range such as the Cascades in the Pacific North West.  On a strike slip fault you may see a fault, such as the San Andreas fault in California.  There are also divergent boundaries like at the mid-Atlantic ridge and Greenland which allows for the formation of new land.  There is also rifting zones, like in Africa, where you would see a large rift.  Also, plumes can come up and cause volcanic island like Hawaii.

Answer 2

Plate tectonics (from Greek τέκτων, tektōn "builder" or "mason") is a theory of geology that has been developed to explain the observed evidence for large scale motions of the Earth's lithosphere. The theory encompassed and superseded the older theory of continental drift from the first half of the 20th century and the concept of seafloor spreading developed during the 1960s.

The outermost part of the Earth's interior is made up of two layers: above is the lithosphere, comprising the crust and the rigid uppermost part of the mantle. Below the lithosphere lies the asthenosphere. Although solid, the asthenosphere has relatively low viscosity and shear strength and can flow like a liquid on geological time scales. The deeper mantle below the asthenosphere is more rigid again. This is, however, not because of cooler temperatures but due to high pressure.

The lithosphere is broken up into what are called tectonic plates —in the case of Earth, there are seven major and many minor plates (see list below). The lithospheric plates ride on the asthenosphere. These plates move in relation to one another at one of three types of plate boundaries: convergent or collision boundaries, divergent or spreading boundaries, and transform boundaries. Earthquakes, volcanic activity, mountain-building, and oceanic trench formation occur along plate boundaries. The lateral movement of the plates is typically at speeds of 50—100 mm/a.[1]

In the late 19th and early twentieth centuries, geologists assumed that the Earth's major features were fixed, and that most geologic features such as mountain ranges could be explained by vertical crustal movement, as explained by geosynclinal theory. 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 once to have fitted together.[2] Since that time many theories were proposed to explain this apparent compatibility, but the assumption of a solid earth made the various proposals difficult to explain.[3]

The discovery of radium and its associated heating properties in 1896 prompted a re-examination of the apparent age of the Earth,[4] since this had been estimated by its cooling rate and assumption the Earth's surface radiated like a black body.[5] Those calculations 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 reasoned it was credible that the Earth was much older, and also that its core was still sufficiently hot to be liquid.

Plate tectonic theory arose out of the hypothesis of continental drift proposed by Alfred Wegener in 1912[6] and expanded in his 1915 book The Origin of Continents and Oceans. He suggested that the present continents once formed a single land mass which had drifted apart thus releasing the continents from the Earth's core and likening them to "icebergs" of low density granite floating on a sea of more dense basalt.[7][8] But without detailed evidence and calculation of the forces involved, the theory remained sidelined. The Earth might have a solid crust and a liquid core, but there seemed to be no way that portions of the crust could move around. Later science proved theories proposed by English geologist Arthur Holmes in 1920 that their junctions might actually lie beneath the sea and Holmes' 1928 suggestion of convection currents within the mantle as the driving force.[9][10][3]

The first evidence that crust plates did move around came with the discovery of variable magnetic field direction in rocks of differing ages, first revealed at a symposium in Tasmania in 1956. Initially theorized as an expansion of the global crust,[11] later collaborations developed the plate tectonics theory, which accounted for spreading as the consequence of new rock upwelling, but avoided the need for an expanding globe by recognizing subduction zones and conservative translation faults. It was at this point that Wegener's theory moved from radical to mainstream, and became accepted by the scientific community. Additional work on the association of seafloor spreading and magnetic field reversals by Harry Hess and Ron G. Mason[12][13][14][15] pinpointed the precise mechanism which accounted for new rock upwelling.

Following the recognition of magnetic anomalies defined by symmetric, parallel stripes of similar magnetization on the seafloor on either side of a mid-ocean ridge, plate tectonics quickly became broadly accepted. Simultaneous advances in early seismic imaging techniques in and around Wadati-Benioff zones collectively with numerous other geologic observations soon solidified plate tectonics as a theory with extraordinary explanatory and predictive power.

Study of the deep ocean floor was critical to development of the theory; the field of deep sea marine geology accelerated in the 1960s. Correspondingly, plate tectonic theory was developed during the late 1960s and has since been accepted all but universally by scientists throughout all geoscientific disciplines. The theory revolutionized the Earth sciences, explaining a diverse range of geological phenomena.

Key principles

The division of the outer parts of the Earth's interior into lithosphere and asthenosphere is based on mechanical differences and in the ways that heat is transferred. The lithosphere is cooler and more rigid, whilst the asthenosphere is hotter and mechanically weaker. Also, 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 the Earth into (from innermost to outermost) core, mantle, and crust. The lithosphere contains both crust and some mantle. A given piece of mantle may be part of the lithosphere or the asthenosphere at different times, depending on its temperature, pressure and shear strength. 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/a (Mid-Atlantic Ridge; about as fast as fingernails grow), to about 160 mm/a (Nazca Plate; about as fast as hair grows).[16][17]

The plates are around 100 km (60 miles) thick and consist of lithospheric mantle overlain by either of two types of crustal material: oceanic crust (in older texts called sima from silicon and magnesium) and continental crust (sial from silicon and aluminium). The two types of crust differ in thickness, with continental crust considerably thicker than oceanic (50 km vs 5 km).

One plate meets another along a plate boundary, and plate boundaries are commonly associated with geological events such as earthquakes and the creation of topographic features like mountains, volcanoes and oceanic trenches. The majority of the world's active volcanoes occur along plate boundaries, with the Pacific Plate's Ring of Fire being most active and most widely known. These boundaries are discussed in further detail below.

Tectonic plates can include continental crust or oceanic crust, and typically, a single plate carries both. For example, the African Plate includes the continent and parts of the floor of the Atlantic and Indian Oceans. The distinction between continental crust and oceanic crust is based on the density of constituent materials; oceanic crust is denser than continental crust owing to their different proportions of various elements, particularly, silicon. Oceanic crust is denser because it has less silicon and more heavier elements ("mafic") than continental crust ("felsic").[18] As a result, oceanic crust generally lies below sea level (for example most of the Pacific Plate), while the continental crust projects above sea level (see isostasy for explanation of this principle

  see http://en.wikipedia.org/wiki/Plate_tecto...

Answer 3

mountains are pushed up and water becomes fetid