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#