Physical Characteristics

Abstract

Icelandic Andosols are predominantly silt loams but coarse textured soils occur on the active volcanic zone and near aeolian sources. Numerous tephra and aeolian layers render stratification of the soils. Bulk density is low (<0.8 g cm⁻³ for Andosols) controlled by the carbon content and allophane at low carbon levels. The Vitrisols (vitric /andic soils of the deserts) are sandy and have higher bulk densities. Icelandic Andosols and Histosols have very high water retention , rapid infiltration rates , and favorable hydraulic conductivities, but coarse tephra layers have negative effects on hydraulic conductivities. Concrete ice forms under desert surfaces in winter, impeding infiltration and causing surface runoff. Lack of cohesion and thixotropic nature make the soils susceptible to water erosion and landslides, but the silt aggregation of allophanic materials makes them vulnerable to wind erosion. Pedon descriptions are provided for nine different soils at the end of the chapter.