Periglacial features developed on the exposed lake bottoms of seven lakes that drained rapidly after 1950, Tuktoyaktuk Peninsula area, western Arcticcoast, Canada

A variety of periglacial features have been studied on the exposed bottoms of seven lakes that drained rapidly after 1950 in the Tuktoyaktuk Peninsula area, western Arctic coast, Canada. Ice-wedge growth commenced as early as the first winter following drainage. In most areas, ice-wedge growth cease within several decades, because of the growth and spread of vegetation whi ch resulted in snow entrapment and increased ground temperatures. At sites where thermokarst lake enlargement had transgressed across terrain with ice -wedge polygons, reactivated polygon patterns developed rapidly in some pre -drainage shallow water areas, with the sites of former troughs becoming ri dges. Excavations across the ridges exposed extensive differential frost he ave, cryoturbations, and slickensided vertical shear planes. Many collapse pits developed because of differential frost heave between silts and sands, cavity formation beneath the frozen silts, and cavity infilling with adjac ent sand in late summer. Other collapse pits developed, either subaqueously prior to drainage or subaerially after drainage. Underground flow has been observed, in early summer, where a near-surface layer of ice-rich silts wa s underlain by desiccated active layer sands at a temperature well below 0 degrees C. At some sites where there has been underground flow some differe ntial loading and water escape features appear to have developed during the thaw period. Copyright (C) 1999 John Wiley & Sons, Ltd.