The tragedy in Nepal is still unfolding as the death toll continues to grow. While causation is still being evaluated, it is pretty clear that a collapsed glacier is at the center of the disaster. Scientists also believe changing permafrost also may have played a role. What are glaciers and permafrost anyhow?

According to the BBC and other media reports, the preliminary thinking is that a collapsed glacier caused a massive rock and ice debris “dam” on the river system. Ultimately, the dam failed, and a large volume water, ice, mud and rock was eventually unleashed in Lende Khola, a tributary of Bhote Koshi river, according to BBC writer Tessa Wong.

“A glacier is a large, perennial accumulation of crystalline ice, snow, rock, sediment, and often liquid water that originates on land and moves down slope under the influence of its own weight and gravity,” noted the U.S. Geological Survey website. They typically form in places with average temperatures near the freezing point and significant snow accumulations. “Over multiple decades this continuing accumulation of snow results in the presence of a large enough mass of snow for the metamorphism from snow to glacier ice process to begin,” the website went on to say.

Though it is a bit early to conclusively link the Nepal tragedy to climate change. It certainly is one of the leading candidates on the table. “Among the most dramatic evidence that Earth’s climate is warming is the retreat and disappearance of mountain glaciers around the world,” said an archived NOAA Climate.gov website. “Based on preliminary data, 2023/24 was the 37 th year in a row that the reference glaciers tracked by the World Glacier Monitoring Service lost rather than gained ice,” it continued. I remember taking my family to Glacier National Park for this very reason. I wanted to see a glacier before they are gone. According to NASA , there were 150 documented glaciers in the Rockies, that number is closer to the low twenties today.

As I wrote last week, the Himalayan region is considered the third pole because it is warming so rapidly relative to other parts of the warming planet. Glaciers will continue to be at risk in this part of the world. Such “sunny day” flooding events will also be an increasing risk factor in the region.

Scientists are also considering what role permafrost may have also played in the disaster. “Thawing of ice-rich permafrost can cause ground subsidence with negative implications for infrastructure, ecosystems, and human lives and livelihoods,” noted a NOAA website report . “Permafrost is any ground that remains completely frozen — 32°F (0°C) or colder — for at least two years straight," explained NASA’s website. While common in higher latitude regions, it is also quite common in high mountains too. NASA estimates that roughly 15% of the Northern Hemisphere land area has permafrost.

Some scientists hypothesize that thawing permafrost compromises the structure and stability of alpine glaciers. “For millennia, the high peaks of the Himalayas were held together by an invisible, frozen cement – permafrost and glacial ice that bound ancient rock into seemingly unshakable fortresses,” wrote Michael Mann in The Guardian . “But as the planet continues to warm, this alpine glue is liquefying,” the noted climate scientist at the University of Pennsylvania warned. Even prior to this event, recent studies have shown that permafrost is thawing in the region and causing subsidence-related risks.

Let’s let the analyses play out, but it certainly is not a stretch to suggest that warming temperatures, thawing permafrost, and a collapsed glacier were in this tragic mix.