deepest hole ever drilled, the Kola Deep borehole in the Russian Arctic, reaches only 0.2 percent the way to the center...even the best scientific maps didn’t look much better than your middle-school textbook cartoon showing an outer crust, an inner core and a thick layer called the mantle in between But that picture is changing. Researchers... are...seeing is full of complex detail...The mantle appears to be layered like an onion, with major transitions 250 miles and 410 miles down. At the 410-mile level, researchers recently identified a tremendous interior mountain range, with peaks perhaps even taller than Mount Everest. “...