Abstract: On May 28, 2025, a high-altitude and long-runout ice-rock avalanche disaster occurred at the Birch Glacier in the Alps of the Valais region in southern Switzerland. This incident completely devastated the downstream towns of Blatten and Ried, leading to the emergency evacuation of over 300 individuals, with one person reported missing. This study presents a systematic investigation into the developmental characteristics, evolutionary processes, and disaster dynamics of the “5•28” Birch high-altitude and long-runout ice-rock avalanche, utilizing multi-temporal satellite remote sensing images, UAV data collected pre- and post-disaster, landquake signal, and on-site video footage. Preliminary results indicate that the Nesthorn Peak, located at a relative altitude of approximately 300 meters on the south side of the upper Birch Glacier, frequently experienced rockfalls driven by a combination of global climate warming and freeze-thaw cycles. While the accumulated debris on the glacier surface suppressed glacial ablation, it enhanced plastic flow, intensified bulging at the glacier front, and promoted the expansion of ice crevasses. Remote sensing interpretation revealed that the glacier area has expanded by approximately 44% over the past decade, with the glacier tongue advancing about 110 meters. During the disaster, around 3.0×10⁶ m³ of wedge-shaped sliding mass experienced high-altitude instability, continually impacting the lower Birch Glacier at a velocity of about 36 m/s. This triggered a total instability involving approximately 6.0×10⁶ m³ of glacial material and its covered debris, which subsequently transformed into a rapidly moving ice-rock avalanche that surged out of the valley at an average speed of 64 m/s, accumulating upon collision with the opposite mountainside. Such high-altitude and long-runout geological disasters, characterized by ice-rock compositions and developed in high-mountains area, are widely distributed throughout the Himalayan orogenic belt in China, posing serious threats to the geological safety of major engineering projects. This research may provide useful references for disaster prevention and mitigation strategies.