2025 Blatten glacier collapse

The Blatten glacier collapse was a natural disaster that occurred on 28 May 2025, affecting the village of Blatten in the Lötschental valley in the canton of Valais, Switzerland. A glacier collapse in the Bietschhorn region caused a landslide which buried and destroyed large parts of the village. The main village had been evacuated since 19 May 2025.

2025 Blatten glacier collapse

Aftermath of the collapse on 30 May 2025
Date	28 May 2025 (2025-05-28)
Time	15:30 (CEST)
Location	Blatten, Switzerland
Cause	Glacier collapse
Deaths	1

Events

Blatten (2007), view from the northwest. The ice and rock masses came from the mountain stream visible at the top right and moved far onto the opposite slope (where the photo was taken). Several houses near the bridge on the left were initially unaffected, but were submerged the next day as a lake rapidly formed.

Initial rockfall at Kleines Nesthorn

Blatten, southeast of it the Kleines Nesthorn, and the Birchgletscher in between (2023 map)

Northwest face of the Bietschhorn seen from Lötschental, with Kleines Nesthorn in front and the Birchgletscher in the center (2019)

Unlike the general retreat of glaciers since 1850, the lower Birch Glacier [de] had advanced about 50 metres (160 ft) in the five years prior to the landslide, likely due to accumulation of weathered rock from repeated rockfalls onto the glacier.^[1] According to Christophe Lambiel of the University of Lausanne, the increased glacier movement is linked to climate change.

The glacier started being closely monitored following a large landslide on 18 December 1993.^[2]

Signs of instability at the Kleines Nesthorn [de] (up to 3,342 m (10,965 ft)) were first observed on 14 May 2025. The peak is about 950 metres (3,120 ft) northwest of the Bietschhorn (3,934 m (12,907 ft)) and lies in a complex geological area of gneiss and amphibolite, subject to erosion and glacier activity. Large rocks fell onto the Birch Glacier and triggered a debris flow that stopped about 500 metres (1,600 ft) above the valley floor and the Lonza River [de].^[3]

Evacuation

Following the debris flow, 92 people were evacuated on 17 May 2025 due to increasing ground movement. On 19 May 2025, all 300 residents were warned and evacuated within two hours. Much of the main village's livestock was also evacuated and some cars were also airlifted out of the danger zone.^[4] Movement of the mountainside had accelerated to 17 metres (56 ft) over three days, raising fears of an imminent collapse. The northeast face of Kleines Nesthorn ultimately slid onto the glacier in multiple phases.

Glacier movement and further collapses

Small rockfall on 19 May 2025

On 19–20 May, around 1.5 million m³ of rock fell from Kleines Nesthorn onto the Birch Glacier, increasing its flow rate noticeably by 21 May.^[5]

The Swiss Seismological Service recorded over a dozen minor rockfalls after 19 May, with magnitudes between 0.3 and 1.6, excluding the main event on 28 May.^[6]

By 24 May, glacier velocity reached up to 4.5 metres (15 ft) per day. The debris pile on the glacier reached 81 metres (266 ft) in height by 25 May,^[7] and the glacier advanced 10 metres (33 ft) per day by 27 May.^[8]

Ideas to artificially blast the glacier were rejected as unfeasible. The glacier tongue reached 2,570 m (8,430 ft), still about 1,000 metres (3,300 ft) above Blatten.

Glacier collapse

The heavily loaded glacier tongue broke off on 28 May, unleashing a massive ice and debris landslide that buried around 130 buildings (approximately 90% of the main village of Blatten) including the village church.^[9]

Roughly 3×10⁶ m³ of rock and large glacier segments fell into the valley. Seismic waves from the event were comparable to a magnitude 3.1 earthquake.^[10]

The total deposit volume reached 10×10⁶ m³ and buried parts of the hamlet of Ried. Weissenried (at ~1,700 m (5,600 ft)) was narrowly spared. The Lonza River became dammed by the debris field over 2 kilometres (1.2 mi) in length and up to 200 metres (660 ft) wide.

One local resident, who was outside of the evacuated area tending to his sheep, was reported as missing. It is believed his around 100 sheep all perished.^[11] On 24 June, human remains were found in the area of Tennmatten.^[12] The remains were later confirmed to be those of the missing shepherd. A criminal investigation was opened to determine why the area where the shepherd was at the time had not been included in the evacuated zone.^[13]

Aftermath

Lonza River blockage

Sediments from the collapsed glacier

Debris blocked the Lonza and Gisentella creeks, forming a lake behind the deposit. Water rose by 80 centimetres (31 in) per hour on 29 May,^[14] but began slowly draining through the rubble by 30 May.^[15]

Partial evacuations in Wiler and Kippel

At 22:30 on 28 May, precautionary evacuations were conducted along the Lonza in the hamlets of Wiler and Kippel due to flood risk from a potential debris dam breach.^[16]

Ongoing risk

On 29 May, over 100000 m³ of unstable rock remained. Additional collapses and debris slides occurred. Cleanup operations were said to be not yet possible due to the ongoing risks pertaining to the instability of the rock and glacier.^[17] The Ferden Reservoir [de] had been preemptively drained to absorb possible floodwaters.^[18] On 30 May, sediment-laden water disrupted operations at the Ferden hydropower plant. Authorities ordered release via its bottom outlet.^[19]

Since the evening of 6 June, the Lötschental has been open again, with Blatten itself still being closed.^[20]

Costs

The Swiss Insurance Association estimated that damages from the landslide reached 320 million Swiss francs ($393 million).^[21]

Map of the affected area

Location of the debris cone (by users of OpenStreetMap)