Impact of the eruptive activity on glacier evolution at Popocatépetl Volcano (México) during 1994 2004
Distribution, rate and magnitude of the glacier changes caused by eruptive activity over 1994-2001 at Popocatépetl Volcano were determined. Digital-elevation models computed by scanned photographs within a digital photogrammetric workstation and the subsequent DEM comparison allowed the determination of glacial changes. The results show that drastic changes occurred in glacier geometry and morphology over 1996-2001: 53% of the glacier surface area was lost due to melting processes. The most important loss occurred over 2000-2001 when 19% of the glacier-covered area disappeared. The glacier volume losses increased over time; during 1999-2000 the largest loss was observed. However, in February 2001, the glacier showed an apparent small increase in volume. Volcanic processes disturbed the mass balance of the glacier, thereby accelerating the ablation processes. The eruptive behavior of Popocatépetl was characterized during this time by alternating periods of explosive events and low activity. Pyroclastic flow generation, ejection of incandescent material, and tephra fall affected the glacier. The tephra volume, distribution and remobilization produced considerable changes on glacier evolution. Tephra deposition on the glacier surface was the most frequent process. The irregular distribution and thickness of tephra provoked differential ablation, and tephra remobilization processes took place on the glacier surface. Together, these processes incised the glacier surface over time. Based on these results and observations, a model of glacier evolution is proposed, involving an adjustment phase, thinning phase, areal-retreat phase, and fragmentation phase. A complex interplay of factors and processes took place between eruptive activity and the glaciers at Popocatépetl Volcano. The glacier evolution and subsequent extinction were induced by the eruptive behavior over the years. While not the only process at work, eruptive activity played the primary role in accelerating retreat and as a consequence in glacier extinction.