* Upper Mantle: This is the uppermost part of the mantle, extending from the base of the crust to a depth of about 660 kilometers (410 miles). It is further subdivided into the lithosphere (rigid, outermost layer) and the asthenosphere (partially molten layer).

* Lower Mantle: This section extends from the base of the upper mantle (around 660 kilometers) to the outer core (around 2,900 kilometers). It is a much more solid and denser region than the upper mantle.

Therefore, while the mantle is divided into two major sections, the upper mantle can be further subdivided into two layers, bringing the total number of "sections" to three.