It's important to note that this layer is not always present. It's found in continental crust only, specifically within the felsic and mafic layers. It's a transition zone between the upper layer (granitic) and the lower layer (basaltic).

Here's a breakdown:

* Continental crust: This is the thicker crust that forms the continents.

* Felsic: Rocks in the upper layer of continental crust are rich in feldspar and silica.

* Mafic: Rocks in the lower layer of continental crust are rich in magnesium and iron.

* Intermediate layer: This layer sits between the felsic and mafic layers and is composed of rocks with a composition in between the two.

The intermediate layer is sometimes referred to as the transitional zone.