Can “layers” be used as in “there are two layers of liquid” although two layers are totally the same?
Ex) Atmosphere consists of 4 layers because 4 layers are totally the same except temperatures.
Should there be something different?
I guess two layers are distinguished only by where they are positioned.
Ex. There are two layers. One layer is positioned at a depth from 0m to 100m, and the other layer is positioned at a depth from 100m to 200m.