An approach to the problem of loess deposit formation: Some comments on the ‘in situ’ or ‘soil-eluvial’ hypothesis

The problem of loess formation has been widely discussed for a long time and in many languages. At the beginning of the 21st century some parts of this debate are still going on. A case is still being made for the ‘in situ’ approach, and there are problems of terminology and mechanism for the Central Asian loess. Consideration of the origin of loess material has now replaced the discussion on deposit formation as the major ‘intrinsic’ problem, and in the world of ground engineering there is still much investigation on the origins of collapsibility, which is, in effect, a discussion of loess origins. There remain some interesting and useful observations to be made on the North African loess and the loess-like materials in Australia, and the ‘desert’ loess controversy is still running. Connections of loess to chernozems, fragipans and rendzinas are becoming clearer, and it seems that it may be possible to appreciate a loess landscape in which the loess contribution is not immediately apparent. Recent SEM observations suggest that collapsibility develops after metastability—as the ‘in situ’ theory appears to imply.