What is another word for sub-stratums?
Pronunciation: [sˈʌbstɹˈɑːtəmz] (IPA) 
One synonym for "sub-stratums" is "underlying layers." This refers to the layers of material that exist beneath the visible surface of the ground or other surface. Another synonym is "subsurface," which refers to anything situated or occurring beneath the surface layer. This term is often used in geology, where subsurface features such as minerals and fossils are studied. "Base layers" is another synonym for "sub-stratums," which refers to the foundational layer upon which other layers are built. The term "foundation" is also used as a synonym, emphasizing the stability and strength of the lower layers upon which everything else rests.
