Abstract Near the edge of Langjökull ice cap there are many soil polygons. A cross-section showed them to be only surface features consisting of rocks in polygonal form embedded in silt. The area revealed much evidence that silt and small rocks often behaved like a liquid upon which heavier rocks would float. If the floating heavier rocks were pushed down into the “liquid,” mud would, in certain circumstances, ooze up a metre or so away. If a number of rocks were depressed the mud would ooze at points roughly equidistant from a few of the rocks, and spread to leave a polygon pattern. Conditions favourable for the sinking of heavy stones in this manner probably occur each spring.