A pedogeographical view of volcanic soils under cold humid conditions: the Commander Islands

• We studied the soils affected by the long-distance volcanic ash input.
• Some of the soils of the Commander Islands are Andosols, and the others are Podzols.
• Bleached layers formed by acid volcanic ash input and reworked by pedogenesis.
• The absence of white layers in some soils should be ascribed to erosion.

We studied two representative profiles at the Bering Island, the Commander Archipelago in the north of the Pacific Ocean. The soils developed in the material of predominantly volcanic origin under cold humid marine climate. One of the soils was classified as an Andosol, and the other as an Albic Podzol. The two soils showed certain similarity in the morphology and properties, thus supporting the hypothesis of their common pedogenetic origin. The study of the composition of a coating of a sand grain indicated complex path of the genesis of the soils: initially the coatings have been formed by allophanes with Fe–humus complexes, then by allophanes with humus, and then by Fe–humus and Al–humus components. The analysis of the total elemental composition, the distribution of the size fractions, and the previously reported data on the mineralogical composition of the soils allowed suggesting a significant contribution of the external volcanic ash from the Kamchatka Peninsula in the genesis of the soils of the Commander Islands. Most probably the whitish layer includes acid volcanic glass transported by the wind. The soils of the (sub)mountainous areas lack whitish layers because of erosion. However, the soils under study do not represent mere mixtures of different ash layers: the newly deposited material was evidently incorporated in the soil profile. We conclude that volcanic soils are specific natural bodies, where sedimentary processes should be taken into account along with the pedogenesis.