Perito Moreno is a vast sea of turquoise ice with undulating wave-like formations full of giant cracks and crevices. It’s not the longest glacier at 30 km or the tallest at 50 to 60 metres high or the widest at 5 km, but it’s incredibly impressive when you’re alongside on the wooden walkways and viewing platforms that bring you right up close. So close, that you can hear the ice cracking and creaking and you’re quite likely to see huge chunks of ice go crashing down into the milky waters below.

It is one of only two advancing glaciers in South America. It sweeps down into the narrowish fjord Brazo Rico opposite Peninsula Magallanes. The glacier has advanced so much in the past that it blocked the five-kilometre fjord isolating Brazo Rico from the Canal de los Tempanos (channel of icebergs) or Brazo Sur and the lake. When this takes place, the pressure from the surrounding water builds up so much that it creates a channel which gets bigger and bigger until it eventually forms an ice bridge. This subsequently ruptures and giant icebergs float off down the Brazo Sur and into the main body of Lago Argentino. And the fjords once again become open channels of water. 

This phenomenon first reportedly happened in 1917, then again in 1940. In the 1950s the glacier blocked the channel for over two years resulting in more severe consequences. Surrounding lands flooded and waters rose over 30 metres. Desperate, the locals tried breaking it up with salt. Then the government, in an ineffectual attempt to unblock the fjord, dropped a few bombs to break it up. The last time the glacier blocked the channel was in 2006.

It’s worth arriving to see Perito Moreno - situated in the southern section of Parque Nacional Los Glaciares - early to avoid crowds and admire it in the early morning sun. The park entrance is on Peninsula Magallanes, on which it is possible to camp. It takes another 35 to 40 minutes to reach the glacier boardwalks by road.