Piles

S t r a t a

stra·ta /ˈstrādə,ˈstradə/
plural form of stratum
stra·tum /ˈstrādəm,ˈstradəm/ noun
plural noun: strata
1. a layer or a series of layers of rock in the ground.
2. a level or class to which people are assigned according to their social status, education, or income.