The oceanic crust is denser than the continental crust mainly due to its composition and thickness. Oceanic crust is primarily made up of basalt, which is a volcanic rock that is rich in iron and magnesium. This composition gives it a higher density, ranging from about 2.9 to 3.0 grams per cubic centimeter.
In contrast, continental crust is mostly composed of lighter granitic rocks, which contain more silica and aluminum. This results in a lower density, typically around 2.7 grams per cubic centimeter. Additionally, continental crust is generally much thicker than oceanic crust, averaging about 30 kilometers compared to the oceanic crust’s average thickness of about 5 to 10 kilometers.
The difference in density between these two types of crust influences how they interact at tectonic plate boundaries. When oceanic and continental plates converge, the denser oceanic crust often subducts beneath the lighter continental crust, leading to various geological phenomena, including the formation of mountain ranges and volcanic activity. Understanding these differences is crucial in the study of geology and plate tectonics.