What are the two main types of crust on Earth?

The two main types of crust on Earth are oceanic and continental. Oceanic crust is primarily found under the ocean and is generally thinner and denser compared to continental crust, which makes up the continents. Oceanic crust is mostly composed of basalt, while continental crust is mainly composed of lighter materials such as granite.

This distinction is crucial in the study of plate tectonics because the interactions between these two types of crust drive geological processes such as earthquakes, volcanic activity, and the formation of mountain ranges. Understanding these two types of crust helps to explain the behavior of tectonic plates as they move over the semi-fluid asthenosphere below them.

The other options provided refer to different geological concepts. Igneous and sedimentary describe types of rocks, but do not pertain specifically to the classification of the Earth’s crust. Basaltic and granitic refer to the composition of rocks within the crust rather than the types of crust itself. Alpine and plate tectonic relate to specific geological formations or concepts but do not classify the crust types present on Earth.