Compressional forces and magma emplacement in an ocean-continent plate convergence zone thickened the continental crust to 65.6 km from its average thickness and lowered the average density to 2.5 g/cm3. How much did the height of the continental crust above the mantle change? (Assume average zcrust = 39.7 km.) Answer must be expressed in km. The height of the crust increased by ___ km..