Jain Metaphysics and Science: 6.1.4 Outer Layers

Three outer layers surround the   loka. The three layers are ghanodadhi layer (dense like water), ghana layer (dense like air) and tanu layer (like rarefied air) as shown in fig 6.1 The first ghanodadhi layer is supposed to support the loka. The second ghana layer supports the first layer and the third tanu layer supports the second layer. The third layer is supported by akasa. The thickness of the three layers is not uniform. At the bottom of lower   loka all three are 20,000 yojana thick. At the level of pitch-dark infernal land ghanodadhi, ghana and tanu layers are 7 yojana, 5 yojana and 4 yojana thick respectively. The thicknesses reduce towards the middle loka, where they are respectively 5 yojana, 4 yojana and 3 yojana. The layer thicknesses increases as we go up and become again 7 yojana, 5 yojana and 4 yojana at the level of Brahma  loka. As we go up further the thickness decrease and become 5 yojana, 4 yojana and 3 yojana near the top of upper loka. The layers are thinnest on the topside of upper loka.