3.3. Weathering indices
Weathering indices were calculated from the geochemical concentration to
see the relative weathering of the volcanic materials. Figure 12 shows
Ruxton index, desilication index, base loss, and Ca loss. Most indices
indicated a progressive weathering sequence from the least to most
weathered soil: Anak Krakatau < Panjang < Rakata
< Sebesi. Nevertheless, the Ruxton and desilication indices,
which reflect the loss of SiO2 indicated the
considerable variation in weathering degree in soils at the Sebesi
island.
Both base cations loss and Ca/Ti ratio confirmed former finding of the
most weathered soils in Sebesi and least weathered in Anak Krakatau.