The law of conservation of energy implies that energy can neither be created nor destroyed, but can be changed from one form to another.
Do you have multiple choice answers? the lower layers are generally older than the higher layers.
Say you have 60 cubic meters of an ideal gas at a pressure of 200 pascals. You heat the gas until it expands to a volume of 120 cubic meters. How much work does the gas do? All you have to do is plug in the numbers:
The gas does 12,000 joules of work as it expands under constant pressure.
