What caused the citizens of the native american town to build another layer on top of the mound?

The correct answer is:

The death of a chief.    

It´s believed that the different cultures that are collectively known as "Mound Builders" would crash one of the wood-and-mud constructions to bury the remains of a deceased chief in a fresh layer of soil, to then raise a new construction on top. Usually, theywere laid to rest in specially developed burial mounds, conical or round.

the first option is correct

mark me brainliest

~courtney