Tronador means "the Thunderer", and the sound that earns the name is ice. Masses of snow and ice break off its glaciers and plunge into the valleys below, a rumble carried for kilometres like rolling thunder. The mountain is an extinct stratovolcano that fell silent around 300,000 years ago, so nothing erupts here; what cracks and falls is the ice itself. Three summits crown it, rising to about 3,491 metres on the border between Argentina and Chile, and eight glaciers spill off its flanks. That makes Tronador the highest peak in Argentina's Nahuel Huapi National Park. At its foot lies Pampa Linda, a hamlet at the end of a forested valley of turquoise lakes and waterfalls, where the wet Patagonian rainforest thins out into bare rock amphitheatres carved by the ice.
The strangest sight here is the Ventisquero Negro, the Black Glacier: a slab of ash-grey ice ending in a milky lagoon, with hanging tongues of ice breaking off and dropping into the water. A steep trail climbs to Refugio Otto Meiling, a hut set above the clouds between the Alerce and Castaño Overa glaciers. From there, roped and on crampons, hikers step onto broad platforms of blue ice scored with crevasses. Nearby, meltwater pours off the cliffs at the Garganta del Diablo, the Devil's Throat, in ribbons you can walk under and come away soaked by. Wherever you go, the distant rumble of falling seracs follows. The ice is in retreat: decades of warming have thinned these glaciers, and the Black Glacier has pulled back so far that it now ends in a growing meltwater lake. The mountain still thunders, but it holds less ice to thunder with every year.