Answer:
mitosis; cytokinesis
Explanation:
See https://humanbiology.pressbooks.tru.ca/chapter/4-13-mitosis-and-cytokinesis/
Zipper fracking is a new technology that produces more oil and more gas, safely and effectively, all from rock formations. Well drilling is another way, you get clean, natural gas by drilling into wells that connect into the ground. All that being said, we could also get chemical energy to be more safer, more usable, more efficient, and cleaner, if people were not careless with their work.
I think the answer is "the older it is"
Reason: I might be wrong but is something (like a shell) gets buried in something (like sand), overtime many things (like dirt, soil, sand, etc.) will be on top of the original. This will make layers. So, the older rock is on the bottom since it has been there for the longest and it gets covered by other stuff (causing the layers).
Hope this helps! :) (If I'm wrong, sorry :( )