Final answer:
The upper layer of Earth consists of two types of crust: oceanic crust, which is about 6 kilometers thick and composed of basalt; and continental crust, which is 20 to 70 kilometers thick and mainly consists of granite.
Step-by-step explanation:
The two types of crust that the upper layer of Earth consists of are oceanic and continental crust. The oceanic crust is generally about 6 kilometers thick and made of basalt, which is a volcanic rock composed mainly of silicon, oxygen, iron, aluminum, and magnesium. On the other hand, the continental crust is thicker, ranging from 20 to 70 kilometers, and primarily consists of granite, another type of volcanic rock. Both types of crust are part of Earth's lithosphere, which is a colder and more rigid layer compared to the underlying mantle. Continental crust, being less dense, 'floats' higher on the mantle than the denser, thinner oceanic crust, allowing the formation of continents and ocean basins. The crust represents only about 0.3% of Earth's total mass, but it is the layer that we are most familiar with, as it forms the surface of our planet where we live and which we can directly study.