Formation of gibbsite aggregates in latosols developed on volcanic ash [Hawaii]

Sherman, George

'The segregation of gibbsite on dehydration into light-colored, irregular-shaped aggregates has been observed in certain Hawaiian soils which have developed on andesitic volcanic ash occurring in the rain forest areas. These soils have been classified by Cline et al. into the hydrol humic latosol soil group. These soils have been developed by the intense and rapid weathering of andesitic volcanic ash under a warm climate having a heavy rainfall ranging from 120 to 350 inches with no season which can be considered dry. Under these conditions, the primary silicate minerals of the volcanic ash have decomposed, and many products of weathering have been leached from the soil. The free and rapid percolation of water has provided conditions favoring the removal of the released soluble silica. The desilication has been accelerated by the organic acids, which are provided by the decomposition of the mixed fern vegetation.' 'The process by which the gibbsite aggregates are formed has not been established. The indications strongly suggest that the alumina has been precipitated from the percolating waters in the pores, cavities, and drainage channels occurring in the soil. The best evidence of this is the fibrous structures often found in these aggregates. The segregation of gibbsite into discrete aggregates may provide a means for its commercial development as a source of alumina.'

Formation of gibbsite aggregates in latosols developed on volcanic ash [Hawaii]

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