* Oceanic crust: This is thinner, denser, and younger than continental crust. It is primarily composed of basalt and gabbro.

* Continental crust: This is thicker, less dense, and older than oceanic crust. It is primarily composed of granite and other felsic rocks.

However, there are further sublayers within these two main layers. For example, the continental crust is sometimes divided into:

* Upper crust: This layer is primarily composed of granite and other felsic rocks.

* Lower crust: This layer is primarily composed of more mafic rocks, such as gabbro and diorite.

Therefore, depending on how you define "layers," the Earth's crust can be considered to have two main layers or more than two layers when taking into account the subdivisions within those main layers.