From ice loss to cascading mass movements: 4D geomorphological analysis of Monte Rosa’s eastern flank (NW-Alps, Italy)

The eastern flank of Monte Rosa (4,634 m a.s.l.), the second-highest peak in the Alps, is among the largest and most extensively glacierized Alpine mountain faces and has been described as a “Himalayan-type” slope. Since the early 21st century, it has been intensively monitored by several institutional teams and academic research groups, primarily due to the exceptional surge event that affected the Belvedere Glacier, the main collector of glacier ice flowing down from Monte Rosa.

Over recent decades, this slope has undergone rapid deglaciation in response to climate change. Ice loss has been accompanied by the onset and intensification of geomorphological instability phenomena spanning the full spectrum typical of glacial and periglacial environments. Rock faces are increasingly prone to toppling, falls and rock avalanches; talus and debris cones are the site of erosion phenomena and feed debris flows; moraines undergo degradation, incision, and collapse. Key drivers include degradation of permafrost, increasingly intense precipitation at high altitude and rising 0°C isotherm. Of particular interest is the high magnitude that characterizes these events, especially if we consider that they occur with an unprecedented frequency.

Mass and energy transfers from high elevations trigger cascading effects across different geomorphological environments (glacial, periglacial) and they ultimately impact the anthropogenic system. Recent geomorphological investigations (CNR-IRPI, University of Turin) and monitoring activities (ARPA-Piemonte) focus on process identification, high-resolution mapping, and quantitative assessment. Two complementary multi-temporal approaches were adopted: (1) field-based and remote-sensing geomorphological mapping, and (2) 3D topographic modelling via photogrammetry. These methods produced detailed geomorphological maps at 1:5,000 scale (years 2010, 2012, 2015, 2018, 2021, 2023, 2024 and 2025) and original 3D photogrammetric models (50 cm resolution: years 2023, 2024 and 2025), which were compared with pre-existing metric-resolution DEMs (2011, 2017).

Data analysis and interpretation for the headwaters of Anzasca Valley (total area: 30 km²) indicate, from 2011 to the present, a total reduction of approximately 1.1 km² in glacierized area and an ice-volume loss of ~56 million m³. The multi-temporal (4D) geomorphological analysis enabled the identification of individual instability processes and the recognition of significant event sequences involving glaciers, rock walls, moraines, and fluvial channels.

These results provide a baseline for assessing where and how geomorphic dynamics intersect with human activities in an area of high value for scientific, mountaineering and tourism interests, recently designated as a geosite of international significance in the latest inventory compiled according to the Piemonte Regional Law 23/2023.