A lot of the mounds were not burial mounds. They were their main council meeting houses. Several years ago I done volunteer work with UT along the Little Tenn. river before Tellico dam was built. We excavated one that was approx 30ft. high and 60ft. dia.
It had been built over a period of approx 150 years. Every few year they would burn it down. They would cover the ashes with a new layer of soil and rebuild. This happened over and over. A layer of soil. A layer of ashes. There was only one burial in it. They figured it was an important chief. There were two other bodies. A woman and baby in the ashes. Probably died in an accidental fire and left there. When we reached the bottom layer thg original post holes were still there. Some had fiiled with dirt but, some were just a hole in the ground. If I remember right, the bottom layer dated around 1400 AD.