Einstein's energy mass equivalence relation say that if the whole given mass is converted to energy then it would be

where
m = mass in kg
c = speed of light in m/s
this is the origination of quantum physics and by this formula we can relate the dual nature of light and particle
So correct relation above will be

Over millions of years, layer after layer of sediment and other plants and bacteria were formed. ... Even higher heat or biomass made predominantly of plant material produced natural gas.
Sorry don’t know this one
Answer:
A force is a push or pull upon an object resulting from the objects interaction with another object
Erosion, weathering, mechanical changes, chemical changes.
Really, any interaction can change the composition of a rock whether it be done by man or through nature.