Congestion in Earth’s mantle: Mineralogists explain why plate tectonics stagnates in some places

Seismic measurements show that in some regions of the Earth’s mantle, plate tectonics stagnates. The causes of the ‘congestion’ of the subducted plate are still unknown. In a new study, mineralogists from Germany explain the phenomenon for the first time.
Source: http://www.sciencedaily.com/releases/2013/03/130331165559.htm