Climate change is devastating glaciers across the planet, with massive loss of ice mass. The glacial melt pools at the base of the glacier are forming into lakes over time. Sometimes, avalanches or landslides falling into these lakes burst the walls holding that water in, similar to a dam bursting, or make it overflow their brims, causing the surrounding and downstream areas to flood. These are called glacial lake outburst floods (GLOFs).

The loss of life and damage these floods can cause is phenomenal. In 2013 the Kedarnath flood left more than 10,000 dead, although unofficial accounts say more than 30,000 were killed. In the Chamoli flood of 2021, more than 70 people were killed and several reported missing.

The sheer physicality of the movement of GLOFs and the devastation they wreak are mind-boggling. To get an idea of what happens when an outburst flood occurs, turning to the East Greenland GLOF would help. Between September 23-October 11, 2024, Catalina Lake, dammed by the Edward Bailey Glacier, gave way, releasing more than 3,000 billion litres of water. Scientists from the University of Copenhagen tracked the flood in real time.

“Imagine an enormous bathtub atop a mountain filled with water equivalent to three times Denmark’s annual water consumption suddenly bursting. This is essentially what happened when the massive Catalina Lake in East Greenland released 3.4 cubic kilometres of meltwater—3,000 billion litres—into Scoresby Sound fjord,” a report quotes them saying.

Speaking of energy release, the report mentions climate scientist Aslak Grinsted as saying: “In this case, the energy released by the glacier flood was equivalent to the output of the world’s largest nuclear powerplant running at full capacity for 22 days.”

Grinsted further says that it’s worth considering how the incredible power of such natural phenomena could be harnessed as a green energy source. The energy produced by the event at Catalina Lake could theoretically have generated 50 megawatts of electricity, enough to power a small town.

The situation of lakes on the hills in India is not lost on India’s researchers. A flurry of research is coming out. “Due to increase in temperatures, glaciers are melting at an accelerated rate,” Anup Upadhyaya, a climate scientist at the Indian Institute of Technology, Kharagpur, tells Hot Rock.

The scale of devastation of the Kedarnath flood of 2013 and the Chamoli flood of 2021 got Upadhyaya to study more about GLOFs. His work is concerned with understanding and identifying which lakes are potentially dangerous in the Northwest Himalayan region. The region comprises Jammu and Kashmir, Ladakh, Himachal Pradesh, and Uttarakhand.

While each flood may have its own trigger, Upadhyaya says it’s often sudden extreme precipitation that undoes the lake. Pieces of the surrounding hills break off into avalanches from the continuous pounding of rain and fall into the lakes, which then burst, unleashing catastrophic floods. Or it could be that the dam holding back the water of the lake fails. Or an earthquake can set off things. Added to these are road construction and hydropower infrastructure. Hydropower infrastructure, in fact, compounded the Chamoli disaster of 2021, as Upadhyaya’s study.

After Antarctica and the Arctic, the Himalayas hold the third largest deposit of ice and snow. As per a 2021 paper published in the journal Nature Scientific Reports, exceptional loss of glacial mass is occurring in the Himalayas, more than any region in the world.

By reconstructing the extent and surfaces of 14,798 Himalayan glaciers during the Little Ice Age, 400 to 700 years and ago, and comparing it with what’s happening now, the researchers say that 40 per cent of glacial area has already been lost.

“The ten-fold acceleration in ice loss we have observed across the Himalayas far exceeds any centennial-scale rates of change that have been recorded elsewhere in the world,” they say.

In the Himalayas, as elsewhere, glaciers retreat and lakes get bigger. In an April 2025 paper published in the journal Environmental Science and Pollution Research, Upadhyaya and Abhishek Kumar Rai analysed the state of more than 1,300 glacial lakes in the Northwest Himalayan region of India. They say that “the Northwest Himalayan region witnessed ~ 8.71% growth in the total area of these lakes (area ≥ 0.01 km 2) from 2018 to 2022, with elevations between 5000–6000 metres exhibiting the most noticeable increase.”

They further state that more than 20 lakes are very high risk, while more than 130 lakes are high risk. The upper Indus basin possessed the majority of vulnerable lakes, which are at a greater risk of experiencing a probable GLOF event, followed by the Jhelum basin.

“What I can say is that it will only get worse. There will be multiple more GLOFs in the future because the glaciers are retreating with the increase in temperature,” Upadhyaya tells Hot Rock.

In fact, a 2023 paper published in Nature Communications states that 15 million people globally are exposed to impacts from potential GLOFs. Populations in High Mountains Asia (HMA) are the most exposed and on average live closest to glacial lakes with ~1 million people living within10 km of a glacial lake. More than half of the globally exposed population are found in just four countries: India, Pakistan, Peru, and China.

Especially nightmarish is the Sikkim disaster. Whatever could go wrong went wrong here, in a catastrophe pile-on. According to the paper in the journal Science, the catastrophe began on October 3, 2023, when a permafrost landslide fell into the South Lhonak Lake, 5,200 metres above sea level in Sikkim. That triggered the GLOF which travelled 385 km along the Teesta River to Bangladesh. Fifty-five people were killed and 74 reported missing in Sikkim. Infrastructure was extensively damaged.

“The severity of these impacts stem from the large volume of water that was released, the massive amount of eroded material, and the recent construction of infrastructure and settlements along the Teesta valley,” researchers say.

To address the threat of GLOFs, there have been suggestions to relocate people from the possible paths of floods, drain lakes, channel flood paths differently, and early warning systems, among others.

The government has initiated flood mitigation measures such as early warning systems. Making inventories of glacial lakes is also a part of mitigation. The Wadia Institute of Himalayan Geology (WIHG) identified 1,266 lakes in Uttarakhand (2015) and 958 in Himachal Pradesh (2018). The Central Water Commission (CWC) monitors 902 glacial lakes and water bodies. It keeps tabs on the expansion of water and spread of lakes.

The Central Government approved the National Glacial Lake Outburst Flood (GLOF) Risk Mitigation Project (NGRMP) for its implementation in four states—Arunachal Pradesh, Himachal Pradesh, Sikkim and Uttarakhand—and allotted Rs. 150 crore. NDMA identified 189 high-risk glacial lakes in the Indian Himalayas.

Perhaps, the most heart-warming saga of glacier collapses comes from Switzerland. On the afternoon of May 28, 2025, an avalanche of rock and ice from the Birch Glacier (Birchgletscher) in southwestern Switzerland roared into the valley below. Debris buried most of the village of Blatten and dammed the Lonza, causing the river to flood. The event occurred after rock from a crumbling mountain peak built up on the glacier, which likely contributed to its collapse, according to this report from NASA.

“Blatten has been wiped away. Erased, obliterated, destroyed, stamped into the ground…The memories preserved in countless books, photo albums, documentation—everything is gone. This is ground zero for Blatten,” The Guardian has the village’s mayor, Matthias Bellwald, saying.

Nobody died, except one who stayed put there. Nobody died because the authorities grew worried about the stability of the mountain and evacuated almost all of the 300 residents