There are two types of crust:

* Oceanic crust: This is the thinner, denser type of crust found beneath the oceans. It's primarily composed of basalt and gabbro.

* Continental crust: This is the thicker, less dense type of crust that makes up the continents. It's made up of a variety of igneous, metamorphic, and sedimentary rocks.

So, while the "top layer" is simply called the crust, it can be further classified into oceanic and continental crust.