Fact of the Day : In the field of geology what is obduction? (from The Oxford Companion to the Earth)
obduction In the late 1960s and early 1970s it began to be accepted that ophiolites (consisting of basaltic lavas, overlying sheeted dykes, gabbro, and peridotite) are slices of oceanic crust and upper mantle that have somehow found themselves exposed on land. Most of the world's oceanic lithosphere is destroyed at subduction zones, below island arcs or Andean continental margins. In those places the oceanic plate descends below an overriding plate and, after providing the stimulus for volcanism on the overriding plate, is eventually absorbed back into the deep mantle. Although it was not clear how or why those particular slivers of ocean floor represented by ophiolites have escaped subduction, a term was required to denote the phenomenon. To meet this need, in 1971 the American geologist Robert G. Coleman introduced the word obduction. The processes of obduction are still not understood, and it is apparent that no two ophiolites have been emplaced in exactly the same manner. However, the term ‘obduction’ has remained a useful counterpart to subduction in the geologist's vocabulary.
Most ophiolites are found in zones of collision or at least convergence between tectonic plates, and they are commonly the only remnants of the floor of a vanished ocean that formerly separated two continents, and which are now firmly sutured together. Small ophiolites along the Alpine– Himalayan mountain chain are of this sort.
Most ophiolites are found in zones of collision or at least convergence between tectonic plates, and they are commonly the only remnants of the floor of a vanished ocean that formerly separated two continents, and which are now firmly sutured together. Small ophiolites along the Alpine– Himalayan mountain chain are of this sort.
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