Beobachtungen an rezenten und fossilen (kaltzeitlichen) Strukturböden

Summary

The shape and structure of stone rings and polygons on level ground and of the stone strips on slopes correspond closely in Spitzbergen and the Alps. Moreover, in both areas the frostsoil or permafrost, which must have remained frozen for several years at a time, undergoes the same changes at the surface during the annual thaw: it is always the pocket of finer soil or, in the case of sloping ground, the deposit of soil between the stone strips which thaws first. Figure 6 shows how, in an alpine stone strip rock structure, the level of the frostsoil sinks in the course of summer and rises again in late summer and early autumn.

A study of the positions of the encased stones shows that about 50% of them lie with their longitudinal axes in the direction of the strips or parallel to the nearest edge of the polygons. Tabulation of our measurements (cf. table of results in Figures 8 and 9) indicates another but lower peak in the figures for stones lying at right angles to these directions.

The establishment of these facts enables us to prove the existence of fossilized stone rings in boulders out-side the terminal moraines of the Würm period. Fossil formations developed when this period of the Ice Age was nearing its end. Since no other cause of preventing the water from permeating can be traced, we assume the existence of permafrost as responsible for the formation of boulders. This assumption allows us to establish a decrease in the average annual temperature of the Würm period. In the Rhine glacier area this decrease amounted to 12 °C.