This is from a photo taken up close, almost inside, an opening along the Aletsch Glacier in Switzerland, the largest in the Alps. This particular cavern is normally frozen shut, and water flowing from the mountainside pools and forms a lake that has, up until recently, always been a year-round landmark. As the glacier recedes, gaps emerge between the ice and rocks. Warmer and longer summers send water rushing through these cracks, carving rivers beneath the ancient ice and accelerates the melting even further, until there is no more lake.