Catching a calving off the Perito Moreno Glacier takes a bit of extra sensory perception, foresight, hindsight and pure, unadulterated luck. In this case, I heard the thunderous cracking, which meant a chunk of ice likely was about to break off, turned my camera in the general direction of the sound and, with my exposure setting already pre-set, I fired off several high-speed continuous shots and was lucky enough to catch this image of a calving in action.