Abstract: Glacial cirques are emblematic features of alpine landscapes. Their formation plays a critical role in the evolution of the divide regions of mountain belts, and their presence is used as an indicator of paleoclimate conditions. Over the last decade, my colleagues and I have sought to better understand the erosional processes responsible for cirque formation and the linked problem of cirque glacier dynamics. Cirques are generally understood to be a consequence of the combined action of glacial and periglacial processes. A prevailing view, dating from seminal fieldwork in the 1950s, of cirque glaciers as rigidly-rotating bodies is wrong and should be abandoned. Another idea, dating from the earliest 20th century, of cirque glaciers as eroding headward through a combination of periglacial weathering and glacial action, is probably correct. To examine this hypothesis, we obtained the first year-round measurements of environmental conditions in the headwall crevasses of cirque glaciers.