A geologic, petrographic and geochemical study has been performed on the pyroclastic flow deposits in the coastal area of
East Zhejiang Province, Southeast China. This study leads to classification of the pyroclastic flow deposits into three
associations: the extrusive type, the surge type and the ash flow type welded tuff associations. Through detailed
investigation and comparison of the characteristics of these lithologic associations, with emphasis on the welded tuffs, a
comprehensive model has been proposed to demonstrate the petrogenesis of the pyroclastic flow deposits.