Argentina's Perito Moreno glacier is one of only a few ice fields worldwide that have withstood rising global temperatures. Nourished by Andean snowmelt, the glacier constantly grows even as it spawns icebergs the size of apartment buildings into a frigid lake, maintaining a nearly perfect equilibrium since measurements began more than a century ago. "We're not sure why this happens," one glacialist said.
Viewed at a safe distance on cruise boats or a wooden observation deck, Perito Moreno's jagged surface radiates a brilliant white and glows deep blue underwater. Water on one side surges until it breaks an ice wall up to 200 feet above lake level, creating a thunderous crash and eliciting applause from tourists. "The glacier has a lot of life," said a guide who leads tours over the glacier's snow fields.