The “old moraines” of Pangnirtung Pass were constructed by trunk glaciers, tributary glaciers, glacial streams, rockfalls, talus-creep and other agents and processes. Rivers have since reworked or removed the deposits lying along the axis of the Pass and have begun to dissect the remainder. The old moraines have ice cores, which have tended to melt, collapse and flow downhill, thus further complicating the drift topography. The freshness of many old-moraine fronts implies a recent warming up of the climate, which is also reflected in the decay of the modern giaciers; but erosional undermining may also cause fresh fronts. Although no accurate date can be assigned to the disappearance of the trunk glaciers, A.D. 500 is given as a tentative estimate. There have since been at least two main advances of the tributary glaciers, of which the first followed close on the disappearance of the trunk glaciers and the second occurred not later than 1850.