Thawing permafrost, the frozen "glue" that holds high mountain rock together, is destabilizing peaks from the Matterhorn to the Himalayas. Dramatic rockfalls have hit the Matterhorn and Mont Blanc massif this year, while a glacier collapse triggered deadly flooding in Nepal, and scientists are now watching a massive slope in Alaska's Prince William Sound for similar signs. Researchers say the mountain freezing line is climbing roughly 100 meters higher each decade, loosening ice that held these peaks together for millennia.