The ice-bridge collapse is a regular occurrence, coming every three to four years according to National Parks Argentina.

Here’s how it works. As the Perito Moreno ice field advances toward the southern arm of Lake Argentina, it creates an ice dam.

As the water builds up behind the dam, it creates a tunnel through the glacier, thus forming the famous ice bridge.

The constant water flow of water through the tunnel gradually eats at the ice, leading to  spectacular ruptures.

The arch of ice that fell was 250 meters (820 ft) wide and 70 meters (229 ft) high –  the height of a 22-story building – and sent massive waves into Lake Argentina, spectators said.