The two main components of the Earth's crust are the continental crust and the oceanic crust. The continental crust is thicker and primarily consists of granitic rocks, making it less dense than oceanic crust, which is primarily composed of basaltic rocks and is thinner but denser. The continental crust forms the landmasses and is typically older than the oceanic crust, which constantly recycles and forms at mid-ocean ridges. Together, these crustal components play a vital role in plate tectonics, influencing geological activities such as earthquakes and volcanic eruptions, as well as supporting ecosystems and human development.