One of the Great Soil Groups, within suborder 1 of the order Zonal Soils of the 1949 USDA system of soil classification, based originally on the work of V. V. Dokuchayev, but now superseded. Tundra Soils are now classified as inceptisols. They occur on ground that drains poorly (mainly because of permafrost), and are acid, are 30–60 cm deep, have a high content of organic matter at the surface, and have a microrelief formed by freezing and thawing; their formation, and the decomposition of organic matter, is inhibited by the low temperature.