earth's surface temperature is assumed to be 15 degrees Celsius in this problem :

(a) The observed geothermal output of the Earth is 4.2 x 1013 W (= 42 TW). Much of this heat escapes at the mid-ocean ridges, but the average continental heat ux is Fa : 65 mW / 1112, as mentioned in class. For normal heat conduction through the Earth's crust, we can write this ux as 1 F = K 1 dz Where K is the crustal material's thermal conductivity and (IT/dz is the vertical tem- perature gradient. Assuming; an average conductivity for the continental crust of K : 3.0 W / 1n / K, estimate the average value of (1T/ dz, in degrees Kelvin per km. (c) At what depth under the continents should the temperature reach the melting point of granite, or N 1200 C? This is the approximate thickness of the continental lithosphere, Below this is the aestherwsphcm, a layer of partial melting and quasiuid behavior where the rigid texttonic surface plates may be thought to 'slide