Final answer:
Continental crust is thicker and composed predominantly of granite, making it less dense than oceanic crust, which is mafic and composed mainly of basalt. The continental crust has higher elevation and is generally older than oceanic crust.
Step-by-step explanation:
Compared to oceanic crust, continental crust on average is thicker. It ranges from about 20 to 70 kilometers in thickness and is predominantly composed of granitic rocks, which are part of a different class of silicates compared to the mafic rocks found in the oceanic crust. Unlike oceanic crust, which is about 6 kilometers thick and composed mainly of basalt, continental crust is made up significantly of granite. This granitic composition is less dense than the basalt composition of oceanic crust.
Continental crust has a lower density primarily due to its granitic composition, leading it to rise higher on the mantle, while the denser oceanic crust tends to sink and form ocean basins. The elevation of continental crust is higher than that of oceanic crust, contributing to the formation of continents above sea level. Additionally, continental crust, unlike oceanic crust, is not more mafic; mafic refers to rock rich in iron and magnesium, which is more characteristic of oceanic crust. Moreover, the continental crust is generally older than oceanic crust, which is continually being formed at mid-ocean ridges and recycled into the mantle at subduction zones.