A piece of the subducted Pacific Plate didn't fully dissolve in the mantle, and currently lives below the Korean Peninsula and E. China. Its complex dynamics have created unique geology, eruptions, behavior, etc. from Mt. #Paektu/#Changbaishan, the active #volcano on the China/N. Korea border which produced the largest eruption in human history 1000 years ago.
Also, fault lines in these subducted plates can reactivate at depth. Earthquakes can happen in the mantle.


