A recent disaster along the border between Tibet and Nepal, which caused hundreds of deaths, was partly due to glacier melt. The cause of the massive floods and debris flows appears to be an ice avalanche, in which a huge piece of glacier collapsed and fell more than 1,000 meters down the mountain into the valley below. This area, known as the High Mountains of Asia (HMA), is sometimes called the "Third Pole" because it holds more glacier ice than any other place outside the polar regions. Many of these glaciers are located along the northern border of Nepal and China, forming a curved range across the Himalayas. Tibet is an autonomous region of China. Nepal is home to eight of the world's 14 highest mountains, all above 8,000 meters. Its northern region is very mountainous and steep, making it prone to landslides, rockfalls, and glacier-related hazards like glacial lake outburst floods and ice cliff collapses. When glaciers move over steep rock slopes, the ice can fracture into structures called seracs—tall, unstable ice cliffs that can break off periodically. Since the start of the industrial revolution, around 1850, the Earth has warmed by about 1.4°C on average. However, this warming varies by region. The Arctic has warmed more than twice as much, and the Himalayan region has also experienced greater warming than the global average. The rate of warming has accelerated significantly over the past 40 years, leading to faster glacier melting around the world. The most detailed study of glacier melting, known as glacier mass balance, uses satellite and ground data to measure melt rates from 1976 to 2024. This study shows that the rate of melting has been higher in the most recent decade than the long-term average in every region except Iceland. In the Himalayan region, the increase in melting is about 25%, while in the European Alps, it is more than double. As glaciers melt, they release meltwater that flows into streams and eventually into larger river systems. However, glaciers often rest on permafrost—ground that remains frozen year-round. As the permafrost warms and thaws, the rock, ice, and mud become unstable, leading to rockfalls and ice instability in steep areas. In the case of the Nepal-Tibet disaster, a block of ice about 600 meters wide and 50 meters thick collapsed, releasing about half a million tons of ice into the valley. Serac collapses are more common during warmer periods when surface melting weakens the ice. That is why mountaineers often try to cross serac barriers at night or in the early morning, before the sun has warmed them. Another effect of glacier melting is the formation of lakes blocked by ice or moraines—debris left behind by retreating glaciers. These lakes can lead to glacial lake outburst floods if the ice or moraine dam fails. Many hiking trails in Nepal and India have warning signs about these potential dangers.