One of the world's few advancing glaciers calves enormous ice towers into Lake Argentino, creating a rumbling, crackling spectacle of geological time made audible.
Most glaciers on Earth are retreating. Perito Moreno is not. While glaciers worldwide contract under rising temperatures, Perito Moreno has remained roughly stable for decades, advancing at approximately 2 metres per day and calving the same amount into Lake Argentino. It is one of the few glaciers on Earth that moves toward you.
The face of the glacier is a wall of ice 5 kilometres wide and 60 metres tall above the waterline. The ice is not white — it is every shade of blue from pale sky to the deep indigo of old compressed ice where no air remains. The blue deepens with the age and density of the ice, and Perito Moreno''s ice can be up to 700 years old in its depths.
Standing on the viewing platforms across the channel, the glacier fills the entire visual field. The sounds are constant and dramatic: cracks that begin deep within the ice and build to rifle-shot snaps, then the rumble of a collapse as a tower of ice shears from the face and plunges into the water. Some of these calving events send ice towers 10 storeys tall into the lake. Waves radiate outward. The fallen ice bobs in brilliant blue chunks.
Every few years, the glacier advances far enough to dam the Brazo Rico channel entirely, building pressure until the ice dam ruptures in a catastrophic flood visible from kilometres away. The last rupture occurred in 2016. The dam is building again.