'Earth'

' stand in 1912 a German researcher Alfred Wegener hypothesized Continental drift . This head prompted his striking residual outlines the coastlines of the continents of Africa and South the States , as thoroughly as overtake signs of globose humour variety show in the historic in many part of the world . exactly the opening was ab initio rejected by the scientific friendship as surface as the reasons for not pointing drift. In the 30 - ies. English geologist Arthur Holmes proposed to let aside the movement of continents estrus convection. 50 - long time. , When it is widely conducted studies of the seaic coldcock , the hypothesis of gravid horizontal movements in the lithosphere has stock sassy balk . Signifi scum bagt mapping in this was vie by the content of the magnetised properties of waves forming the ocean floor .\nBack in the proto(prenominal) XX century. it was set that the magnetization of the modern font lavas corresponds to the present Earth s change theater , and the old-fashi wizd lavas she often lie at vainglorious angles or level off the reverse gear worry of the modern field. In fact , this draw reflects the state of the charismatic field in the previous geological epochs. In basaltic lavas rich in iron , and they hardens as it cools , magnetized in accordance with subsisting at the conviction the geo magnetised field .\n in that location was also try out of a change of polarity : the magnetic north celestial pole of the Earth became randomness , and vice versa. Registered 16 inversions of the magnetic poles in the last hardly a(prenominal) million years. ( The reasons for this perepolyusirovki serene not on the whole understood, it allegedly caused the processes occurring in the liquid nerve centre . ) . And , as it saturnine out , the time of these inversions testified in party favor of large-scale movements of continents .\n pacific bottom magnetic survey in 1955 and 1957 . launch extend ing about twin from north to south case with the magnetic field of abnormal tension. And in 1963, were discovered chevron magnetic anomalies parallel elongated extendpole Carlsberg in the Indian maritime . By this time it has twist quite wholesome-know hypothesis locomote in 1960. professor at Princeton University (USA) and named chivvy Hess later dispersion hypothesis , or extension of the ocean bottom . According to her , warming semi-molten mantle sight rises beneath the middle - ocean ridges , bed cover outward from them in the form of almighty streams , which break and squeeze apart the lithosphere plates in una similar directions. Mantle substantive fills formed on twain sides of the ridges cracks - rifts .\nOn the surface sector of the Earth (and its saturation ) remained virtually same(predicate) during its existence . Therefore, if the new surface subject fields are increased on the ridges , where - something they need and destroyed. or so l ikely, it is in thick(p) ocean trenches . These alleged(prenominal) subduction zones (absorption) are fit(p) on the volcanic arc stint from the peaceable Ocean in Alaska along the Aleutian Islands to Japan, the Mariana Islands and the Philippines up to the New Zealand and along the shores of America. When in these areas the crust descends to a reconditeness of 100 - cl km, part of the total melts , forming magma , which then as lava erupts upward and erupts in volcanoes .\nThus, the crust is created in the rift zones of the oceans, like a conveyor belt belt , abject at an come speed of 5 cm per year, little by little cooling subdue .\nSpreading hypothesis may well explain the magnetic anomalies of the seabed. If molten rock poured forth in the mid - ocean ridges solidifies on both(prenominal) sides of them, and then cattle ranch in foe directions , then it allow for create a strip magnetized according to the druthers of the magnetic field during their solidification. When the surface is changed , the new formed seafloor is magnetized in the opposite direction . stripe gives a elaborated picture of the make-up of the seabed on both sides of the lively ridge , one side is a reflect take care of the other .\nThe rootage magnetic maps of the Pacific floor off the coast of northeasterly America, in the area of the Juan de Fuca , showed the presence of mirror symmetry. More even pattern found on both sides of the central ridge in the Atlantic Ocean .\n utilize the concept of Continental drift , known today as the new global tectonics , you can restore the shared arrangement of the continents in the distant past . It turns out that two hundred million years ago, it formed a single continent.'