Characteristics of Soils Derived from Tephra and Pyroclastic Flow Deposits from Taal Volcano, the Philippines

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The various morphological, physieo-chemieal and mineralogieal properties of soils derived from tephra and pyroelastic flow deposits of the Taal volcano were characterized and evaluated. 1. As compared with the pumiceous sandy soils of Mt. Pinatubo, soils of the Taal volcano showed generally a finer texture (silty clay to clay) with the exception of the base surge materials consisting of loam. 2. Parent ashes ranged from basaltie-andesite to basalt, as compared with andesitie to dacite for Mt. Pinatubo. Lithologie nature as well as the age of the tephra seemed to account for the advanced degree of weathering and resultant high clay content in the Taal soil. 3. Clay consisted predominantly of crystalline silicate mineral dominated by halloysite. Dominance of crystalline clay could be due to the ustie moisture conditions with a long dry period. In common with Mt. Pinatubo soils, soils of the flood plains were dominated by 2:1 clay minerals. 4. Based on the data on andic soil properties the soils studied could not be classified as Andisols. Basically, the typical andie soil properties did not develop under a ustie soil moisture regime which contributed to the clay mineral composition. Two of the pedons examined in this study were classified as Andie Eutropepts while on the pedons studied had been classified as Ustarent.
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