The Genesis and Morphology of Hawaiian Ferruginous Laterite Crusts

Hawaiian soils having hard sterile surfaces have been described by Sherman et al; 1 Published with the approval of the Director of the University of Hawaii Agricultural Experiment Station, Honolulu, T. H., as Technical Paper No. 196. Manuscript received March 16, 1950. "Chairman, Department of Soils and Agricultural Chemistry, University of Hawaii Agricultural Experiment Station. MASSIVE FERRUGINOUS SOIL HORIZONS have Preez (1949) has modified Pendleton's defbeen discovered in the profiles of certain inition in that he describes a laterite to be a Hawaiian soils which have morphological vesicular, concretionary, cellular, vermicular, characteristics similar to the ferruginous latsJaglike pisolitic or concrete-like mass conerite crusts found in other tropical areas. sisting chiefly of ferric oxides with or without Likewise, the nature of the soil weathering ' mechanically entangled quartz and minor responsible for these ferruginous horizons ,quantities of alumina and manganese; it is bears a great resemblance to that described of varying hardness but it is usually easily for other ferruginous horizons. However, the shattered when struck a sharp blow with a ferruginous soil horizons found in the Hahammer. Du Preez 's definition differs from waiian Islands -do not have the hardness Pendleton's in that it does not require a de' which is described for ferruginous crusts in gree of hardness to meet the requirements of India or Indo-China. In spite of the lack of a material suitable for building construction. thisdegree of hardness the author feels that Botelho da Costa and Lobo Azevedo (1949) the Hawaiian soils which have' a hard ferhave objected to a definition of a laterite ruginous surface or near-surface horizon are which requires the presence of a concretionary the equivalent of the ferruginous laterite ferruginous layer. In general, Du Preez's defcrust of other tropical regions. It is the purinition has considerable acceptance. pose of this article to describe the genetic and Sherman (1949) has pointed out that the morphological characteristics of the Hawaiian laterite crust will be the end product of troplaterite crlisrs and to show their similariry to ical soil weathering under an alternating wet other described laterite crusts. and dry season. He has suggested that under The original description of a laterite was continuous moist soil conditions the ultimate made by Buchanan (1807), who defined it end product of soil weathering in the tropics as a ferruginous indurate clay which.is brickwill probably be a soil rich in alumina. The , like in nature. Pendleton (1946) , a firm ferruginous layer whichoccurs at or near the follower of Buchanan, has defined a laterite surface is called a laterite crust in that it is as follows: "Illuvial horizon largely iron oxusually a hard sterile soil area. The ferruides" slaglike, cellular or pisolitic structure, ginous layer may be found below the surface and of such a degree of hardness that it may which may have resulted from erosion or by be quarried out and used for building conformation over the water table in coarsestruction. " Many of the temples in tropical textured soils. The ferruginous layer which Asia are built of these laterite materials, Du develops in the fine-textured soils materials forms below the surface and is later exposed by erosion as sterile hard surface soil.