腾冲火山灰土形成于第四纪火山碎屑喷出物,通常土壤为酸性,土层中含有多少不等的浮岩和其他形式的熔岩块。A层色暗、有机质含量和持水量都很高、容重特低。粘粒矿物中有显著量的水铝英石。基质含有大量细粒腐殖质和玻璃碎屑。肥力高,能高产。成土作用主要是岩成草甸过程的有机质大量积累和富铁铝伴有表土层的生物富硅作用。该土的许多发生特性与国外的火山灰土相似。鉴于该土受母质的影响深刻和与附近地带性土壤的差异,在分类上可定为岩成土纲中的一个特殊土类,名为火山灰土。 Tengchong volcanic ash is formed in the Quaternary volcanic debris discharge, usually acidic soil, the soil contains varying amounts of pumice and other forms of lava. A color dark, organic matter content and water holding capacity are very high, very low bulk density. Clay minerals have a significant amount of allophane. The matrix contains a large amount of fine-grained humus and glass crumbs. High fertility, high yield. The main soil-forming effect is the accumulation of organic matter in the process of rock formation and meteoric enrichment of silicon in the iron-rich aluminum accompanied by topsoil. Many of the characteristics of this soil are similar to those of volcanic ash from abroad. In view of the profound influence of the soil by the parent material and the difference with the zonal soil nearby, it can be categorized as a special soil type named as pozzolana in the rock formation.