During this vast time [of the split of Pangea] the sea waves have been continuously pounding against Africa and Brazil and in many places rivers have been bringing into the ocean great amounts of eroded material, yet everywhere the geographic shore lines are said to have remained practically unchanged!
However, his ideas were not taken seriously by many geologists, who pointed out that there was no apparent mechanism for continental drift.
Plate boundaries are commonly associated with geological events such as earthquakes and the creation of topographic features such as mountainsvolcanoesmid-ocean ridgesand oceanic trenches. There are essentially two main types of forces that are thought to influence plate motion: The hypothesis of continental drift was largely developed by the German Alfred L.
The manifestation of this varying lateral density is mantle convection from buoyancy forces. He called his southern supercontinent Gondwanaland and the northern land mass Laurasia. However, within a few decades that was all to change. Dietz and Hess the former published the same idea one year earlier in Nature but priority belongs to Hess who had already distributed an unpublished manuscript of his article by  were among the small handful who really understood the broad implications of sea floor spreading and how it would eventually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 An overview of the plate tectonics theory by alfred wegener like Holmes.
Most people observed the apparent surface similarities of the two coasts, but Wegener was the first to look into how the continents fit together at their respective continental shelves. Another issue that hurt the hypothesis was the mechanism that Wegener proposed to initiate continental drift.
Either side of a spreading centre, weak magnetic anomalies km wide and hundreds of kilometres long can be identified. They were all inspired by the remarkable fit between the Atlantic coasts of Africa and South America. 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.
Most earthquakes occur in narrow belts that correspond to the locations of lithospheric plate boundaries. As one of the plates is subducted beneath the other it begins to melt at a depth of between 90 and km and the resulting magma rises to the surface above the subduction zone to form a chain or arc of volcanoes.
His paper, though little noted and even ridiculed at the time, has since been called "seminal" and "prescient".
Specifically, they did not see how continental rock could plow through the much denser rock that makes up oceanic crust. Paleontologists had also found that there were fossils of similar species found on continents that are now separated by great geographic distance.
Du Toit was confident he had found conclusive proof that the continents were once joined.
However, despite his range of evidence, the continental fits were not perfect and the geological match-ups were not always consistent while the continental fit left some gaps when using the current coastline, it was demonstrated in the s that using a m depth contour gives a much tighter fit.
Continental drift 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.
This distortion was recognized by Icelandic mariners as early as the late 18th century.
The key principle of plate tectonics is that the lithosphere exists as separate and distinct tectonic plateswhich ride on the fluid-like visco-elastic solid asthenosphere.
Strong earthquakes can occur along a fault. Apart from using the fit of the two continents already mentioned, Wegener also used fossil distribution and lithological similarity as evidence. These elevations were the ocean abyss and the contiental crust.
As he later wrote: 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. Definition and refining of the theory 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: Therefore, Heezen advocated the so-called " expanding Earth " hypothesis of S.
This is certainly true of plate tectonicsone of the most important and far-ranging geological theories of all time; when first proposed, it was ridiculed, but steadily accumulating evidence finally prompted its acceptance, with immense consequences for geology, geophysics, oceanography, and paleontology.
Death Wegener died in Clarinetania, Greenlandin November This activity required him to travel constantly between various weather stations in Germanyon the Balkanson the Western Front and in the Baltic region.
Most of the Earth's tectonic, seismic and volcanic activity occurs at the boundaries of neighbouring plates. In the early s 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.
Here is a modest sample: These long linear strips of magnetic anomalies form a symmerical pattern either side of a spreading centre. They are associated with different types of surface phenomena. Wegener was not the first to note this Abraham OrteliusAntonio Snider-PellegriniEduard SuessRoberto Mantovani and Frank Bursley Taylor preceded him just to mention a fewbut 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.In line with other previous and contemporaneous proposals, in the meteorologist Alfred Wegener amply described what he called continental drift, expanded in his book The Origin of Continents and Oceans and the scientific debate started that would end up fifty years later in the theory of plate tectonics.
Even though the theory of plate tectonics is now widely accepted by the scientific community, aspects of the theory are still being debated today. Ironically, one of the chief outstanding questions is the one Wegener failed to resolve: What is the nature of the forces propelling the plates?
Plate Tectonics: The Rocky History of an Idea. In Alfred Wegener () Wegener's drift theory seemed more plausible than land bridges connecting all of the continents.
But that in itself was not enough to support his idea. Another observation favoring continental drift was the presence of evidence for continental glaciation.
Plate Tectonics Overview. Last Updated on Tuesday, 27 June | | | Hits: The hypothesis of continental drift was largely developed by the German Alfred L. Wegener, a lecturer in astronomy and meteorology, who suggested that the Earth's continents had at one time been joined in two supercontinents.
From these simple observations. Plate Tectonics and the Scientific Method Plate tectonics was originally called the “Theory of Continental Drift” originated by Alfred Wegener.
History of plate tectonics.
Plate tectonic theory had its beginnings in when Alfred Wegener proposed his theory of "continental drift.".Download