What is the Earth's crust made of?

The outermost layer of our planet, called the crust, is made up of minerals in the form of solid rock and loose dirt. The crust sits atop the mantle, although the liquid magma of the mantle sometimes breaks through. When this magma cools, it hardens into part of the outer crust. In some places, like the bottom of the ocean, the crust is quite thin. The crust is far thicker when it is part of land masses. We call the crust that makes up land masses the continental crust, and the composition here is primarily granite rock. The oceanic crust at the sea-floor has higher levels of basalt and gabbro rock. Both kinds of crust also contain the minerals aluminum, uranium, iron, and silicon.