Why it’s so hard to predict a tragedy like Nepal’s glacier collapse

On August 26, the side of a mountain near the border between Nepal and Tibet collapsed. Seven billion cubic feet of glacial ice and rock, enough to fill 100 football stadiums, crashed roughly a mile straight down into the river below. The impact created a muddy wall of water that swept through the valley as fast as 100 miles per hour, destroying villages dozens of miles downstream and killing more than 1,300 people. Thousands more remain missing.  The scale of the disaster is extraordinary, even for a region accustomed to deadly floods and landslides. It will take months for scientists to confirm exactly what happened. But, they warn, one thing is already clear: As climate change melts icy landscapes worldwide, tragedies like this are more likely to happen. They are also incredibly hard to predict. “Glacial loss destabilizes slopes in many far-reaching ways that are often unpredictable and catastrophic,” said Mark Carey, a professor of environmental studies and geography at the University of Oregon who leads a lab that studies glaciers. Proactive research and monitoring have saved lives in some parts of the world, Carey said, but in a place like the Himalayas, where thousands of glaciers are spread over vast areas, “it’s impossible to predict everything and establish early warning systems everywhere.” The world’s glaciers have shrunk -fifth in the last century and are expected to lose at least another quarter of their mass by 2100. Each fraction of a degree of warming makes them vanish faster, with hundreds of billions of tons of ice lost each year. To support our nonprofit environmental journalism, please consider disabling your ad-blocker to allow ads on Grist. Here's How The downstream effects of this disappearing ice are complex and varied. Glaciers often buttress the sides of mountains and, as they retreat, newly exposed silt and rock can become unstable. The soil itself is also often glued together by a frozen layer known as permafrost, which helps lock slopes into place, but thaws when temperatures become too warm. Glacial meltwater can eat into the cracks in the bedrock, weakening it over time. All of these processes can result in sudden avalanches or rock slides — like one that caused a 1,500 foot tsunami in Alaska last summer, or possibly like the collapsed mountain slope in Nepal. It’s also common for retreating glaciers to leave behind ridges of dirt and rock, known as moraines, that trap meltwater and rain.