The lowermost portion of this region is known as the D'' [d prime prime] layer.
The lowermost portion of this region is known as the D'' [d prime prime] layer. It is often modeled as two layers separated by the 670-kilometer discontinuity. Evidence for this region's being hotter during the Archaean eon includes the abundance in cratons of komatiitic [coh-ma-tee-IT-ic] lava. Its upper portions are home to the low seismic velocity zones, and it is bounded below by the Gutenberg discontinuity, which separates it from another convecting region. Plumes of molten rock rise through, FTP, this layer of the Earth separated by the Moho discontinuity from the crust.
The lowermost portion of this region is known as the D'' [d prime prime] layer.
{mantle}