Temper, clay

Vertisols > 30% shrink-swell clays, cracking in dry season, deep A Temperate to subtropical grasslands... 

Two substrate materials were used for most of the measurements. They were chosen as representative of two types of environmental material found in actual fallout. The first was a clay loam occurring in the Berkeley Hills, Calif. This is a more-or-less typical example of a silicate soil found in extensive areas in the temperate zones. The second material used was a calcium ferrite. This material has been observed in fallout resulting from nuclear explosions at the Pacific Proving Grounds where large amounts of calcium oxide, derived from the coral sand, and iron oxide, derived from towers, barges, or other structures, have been fused together. 

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