Question #0703f

1 Answer
Dec 6, 2017

\delta_{"cc"} = (\frac{\rho_{oc}}{\rho_{"cc"}}).\delta_{oc} = \frac{3\quadg.cm^{-3}}{2.7\quad g.cm^{-3}}\times 4\quad km = 4.4\quadkm

Explanation:

Consider an area A and measure the crustal mass within that area. If the crustal thickness is \delta, then the crustal volume within this area is A.\delta

Mass of oceanic crust: \quad M_{oc} = \rho_{oc}.A.\delta_{oc}......(1)
Mass of continental crust: \quad M_{"cc"}=\rho_{"cc"}.A.\delta_{"cc"} ...... (2)

To have the same crustal mass (i.e M_{oc}=M_{"cc"})

\rho_{oc}.cancel{A}.delta_{oc} = \rho_{"cc"}cancel{A}.\delta_{"cc"}
\delta_{"cc"} = (\frac{\rho_{oc}}{\rho_{"cc"}}).\delta_{oc} = \frac{3\quadg.cm^{-3}}{2.7\quad g.cm^{-3}}\times 4\quad km = 4.4\quadkm