Which depth often separates the upper and lower mantle in the historical two-layer convection model?

Answer

The $660 ext{ km}$ boundary

Many historical models assumed a two-layer system based on seismic velocity discontinuities, specifically the $660 ext{ kilometer}$ boundary that separates the upper mantle from the lower mantle.

Which depth often separates the upper and lower mantle in the historical two-layer convection model?

#Videos

Mantle Convection explained by Peter Bunge - YouTube

GeologyEarthconvectionmantledrive