Like the snowfields of Kilimanjaro and the ice in the Diamond Couloir, the Lewis Glacier is shrinking at an alarming rate because of global warming.
CNN: The snows of Erukenya
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The pair had set out on a popular summer hike known as Le Couloir des Bossons near Mont Blanc - the Europe Union's highest peak.
BBC: UK father and son found dead in Alps are named
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The massif's two highest peaks, Nelion and Batian, rise to more than 17, 000 feet, with 1, 000-foot-vertical walls leading to their summits and the famous Diamond Couloir in between.