Question

Why is ocean crust mostly mafic and continental crust more felsic?

A) Continental crust has a higher density than oceanic crust.
B) Oceanic crust is older and has undergone more weathering.
C) The process of seafloor spreading produces mafic oceanic crust.
D) Continental crust is composed of lighter minerals, making it felsic.

Answer 1

Ocean crust is mostly mafic due to the composition of mafic magma that forms basalt, which occurs from seafloor spreading, while continental crust is more felsic because it consists of granite with lighter elements and lower density.

Step-by-step explanation:

The ocean crust is mostly mafic because it is composed of mafic magma that cools to form basaltic rocks, which are rich in iron and magnesium.

This occurs during the process of seafloor spreading, where magma rises from the mantle at divergent boundaries to create new oceanic crust. In contrast, the continental crust is more felsic because it is composed predominantly of granite, an igneous rock with a higher composition of silicon and oxygen, which are lighter elements.

Since granite has a lower density, continental crust does not sink into the mantle as oceanic crust does, resulting in it being thicker and forming the continents above sea level.