Geodynamic Quiz 8: Heat
Read Chapter 7 through (and including) section7.3.3
1. At the surface of the earth, there are two primary heat sources, the sun and the earth:
a) Heat from the sun is ~10,000 x the heat from the earth
b) most of the heat from the sun is re-radiated back into space
c) Heat from the earth is ~0.09 W/m2
d) all of the above are true
2. Within the earth, the primary ways that heat moves are:
a) conduction, convection, radiation, and advection
b) conduction
c) convection
d) conduction, convection, and advection
3. Within the earth’s lithosphere and outer core, the primary way that heat moves is
a) conduction, which is much slower than convection
b) conduction, which is much faster than convection
a) convection, which is much slower than conduction
b) convection, which is much faster than conduction
4. Thermal conductivity (k)
a) is a measure of the ability of a material to conduct heat
b) is ~ 1.7 to 3.3 W/m·°C for rocks
c) is greater for aluminum than Styrofoam
d) all of the above are true
5. Heat is generated within the earth. Within the crust
a) the decay of K, U and Th is the main source of heat generation
b) faults are thought to generate heat via shear heating
c) the cooling and solidifying of magma (the latent heat of the magma) can be a source of heat
d) all of the above are true
6. Thermal diffusivity (κ) is
a) k/(ρ cp)
b) the ability of a material to loose heat by conduction
c) is a function of thermal conductivity, density, and specific heat
d) all of the above are true
Equation 7.28 calculates the equilibrium geotherm (equilibrium means the temperature does
not change with time), and figure 7.3 shows example geotherms calculated with this equation.
Question 7 through 9 refer to this equation and figure
7. Increasing the conductivity of the crust will
a) decrease the temperature at the base of the crust
b) increase the temperature at the base of the crust
c) have no effect on the temperature at the base of the crust
d) all of the above are true
8. increasing the heat generation within the crust will
a) decrease the temperature at the base of the crust
b) increase the temperature at the base of the crust
c) have no effect on the temperature at the base of the crust
d) all of the above are true
9. increasing the basal (mantle) heat flow will
a) decrease the temperature at the base of the crust
b) increase the temperature at the base of the crust
c) have no effect on the temperature at the base of the crust
d) all of the above are true