Autopsy (geology)
Postmortem (after Latin obduco draw about something ',' cover ') referred to in the geology of the thrust of continental crust by oceanic crust .
Contrary to popular belief, autopsy is not simply the opposite of the process of subduction , because oceanic crust is denser and therefore heavier than continental crust and is therefore almost always subducted instead of autopsy. Autopsy is therefore the exception to the rule. It only happens under very specific conditions and only in geologically short periods of time.
One possible situation in which oceanic crust shifting onto a continent can occur is accretion wedges . Here, during subduction, the oceanic crust of the lower plate is not completely drawn down into the upper mantle (subducted), but sheared from its base and pushed onto the continental crust of the upper plate . For this, the continental crust itself must have been bent down into the subduction zone for some time before it lifted out again due to its lower specific weight , and with it the sheared off remnants of the oceanic crust.
The best-known example in this context are narrow strips of ophiolites , which are found in fold mountain belts and which are believed to be the last remnants of entire oceans that have disappeared between two colliding continental blocks.
literature
- Wolfgang Frisch, Martin Meschede: Plate tectonics. Primus-Verlag, Darmstadt 2005. ISBN 3-89678-525-7