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DESCRIPTIONContinental drift. Valeria Urhan. Continental drift. - PowerPoint PPT Presentation
Ocean Currents and Density
Continental driftValeria Urhan
Continental driftContinental drift is the movement of the Earth's continents relative to each other by appearing to drift across the ocean bed. The speculation that continents might have 'drifted' was first put forward by Abraham Ortelius in 1596. The concept was independently and more fully developed by Alfred Wegener in 1912. The theory of continental drift was superseded by the theory of plate tectonics, which explains how the continents move.TECTONIC PLATES
Wegeners theoryThe similarity of southern continent geological formations had ledRoberto Mantovanito conjecture in 1889 and 1909 that all the continents had once been joined into asupercontinent(now known asPangaea); Wegener noted the similarity of Mantovani's and his own maps of the former positions of the southern continents.
Throughvolcanicactivity due tothermal expansionthis continent broke and the new continents drifted away from each other because of further expansion of the rip-zones, where the oceans now lie. This led Mantovani to propose anExpanding Earth theorywhich has since been shown to be incorrect.Some sort of continental drift without expansion suggested that the continents were dragged towards the equator by increased lunar gravity during theCretaceous, thus forming the Himalayas and Alps on the southern faces.
GEOLOGICAL TIME SCALEtands for the Quaternary period.