The Kaiserstuhl is today largely covered by a Quaternary loess layer, a loosely cemented sediment. It is derived from other rocks through erosion and is then transported by the wind. The loess at the Kaiserstuhl - as in all the peripheral areas of the Upper Rhine Valley - was formed during the last Ice Age. Large parts were bare of vegetation and so loess was winnowed out from the Rhine sediments. It was then deposited in the periglacial area (i.e. ice-free, but surrounded by glaciers) at the Kaiserstuhl. The major process active here was frost weathering resulting in crushed rocks. The wind blew strongly, as there was no vegetation that could have moderated it - entraining the lightest material and depositing it at obstacles like the Kaiserstuhl. Deposition took place northeast of the Kaiserstuhl, as the winds blew from the southwest.