Which is denser, the granitic rock of the continents or the basaltic rock of the ocean floors?

Question

A. granite rock of the continents
B. basaltic rock
C. They have about the same density.

Which extends deeper into the crust, the continents or the ocean floors?

A. the ocean floors
B. They both extend about the same distance into the crust.
C. the continents

Answer 1

Basalt is 3300 kg/m^3 and granite is 2800 kg/m^3, so basalt is clearly denser. As such it lies lower in the crust. Oceanic crust is about 5 km thick and continental crust is about 35 km thick so (I think) continental crust extends deeper into the mantle. This question could have been phrased better, so I'm not sure what your teacher was asking. Clearly, continental crust is thicker, both above and below, than oceanic crust. But how can "the ocean floor" extend into the crust when it is the top part of the crust? You will have to trust to your judgment on that one.

Answer 2

According to this page: http://www.geocities.com/unforbidden_geology/rock_properties.htm
The basalt is denser and harder than granite