Anyone care to comment?
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I suppose it's possible, it could have happened eons and eons ago. Subduction is a part of Plate Tectonics. (You can find more subduction entries. At the top left in your browser menu, select Edit and then Find on this page. A small window will appear. Type in the word subduction)
This page has some animations illustrating Plate Tectonics. Maybe it happened during the Continental Drift (refresh the page to see it again).