TWO TYPES OF CATASTROPHIC GLACIAL ADVANCE

Abstract

The sudden, rapid advance of the snouts of certain mountain galciers has long been familiar. Systematic study of these phenomena began in 1956, with the catastrophic advance of the snout of the Muldrow Glacier in Alaska. According to A.S. Post a surge wave caused this advance. The next major glacial catastrophe was the advance of the Medvezhye Glacier in the central Pamirs in 1963. Unlike the Muldrow Glacier, the Medvezhye Glacier was intersected by an ice fall. and has periodic occurrence. The author surveys the characteristic indicators of surge and pulsating glaciers. Surge glaciers have relatively smooth surfaces, with smooth transitions from the ablation zones to the accumulation zones. In the quiet period they show no increase in their thickness. Pulsating glaciers exhibit a pronounced continuous buildup of thickness during the quiescent period and often are broken into two parts by an ice fall which separates the part of the glacier subject to catastrophic advances from its upper zone which remains in a relatively quiescent state. of catastropes.