The heat of the Earth's interior comes from which of the following sources?
a) radioactive elements
b) gravity
c) the sun
d) both a & b

Ahis which describe the horizons in a soil profile? check all that apply. horizon a is mineral deficient. bedrock lies below the soil layers. te horizon o forms from organic material, horizon b undergoes the least amount of change. horizon c is least affected by the soil formation process.