I walked the Alps’ largest glacier. It felt like ‘last-chance tourism’

21.07.2023 - 13:59 / theguardian.com

Seven of us are roped in a line, with hiking poles in our hands and crampons on our boots. Led by our guide, David, we take it in turns to step from rock into the marbled grey ice beyond. I hesitate before taking my step; the act feels oddly disrespectful. It takes a few minutes to trust that the spikes will hold their grip, but I get used to the crunching rhythm and the occasional tug of the rope. The summer sunshine is warm but a coldness radiates from below. It is a six-hour hike to the hut we will sleep in tonight.

This is the Aletsch glacier in Switzerland’s Bernese Alps. It is 15 miles long and up to 800 metres deep, the largest and longest glacier in the Alps. From above, its mass looked uniform, but up close it is creased and contorted, speckled with browns, blacks and greys, and glimpses into its deep crevasses reveal a startling turquoise. Two gritty parallel lines follow its long curve downhill, moraines that act as conveyor belts bearing rocks and rubble. As David reminds us, the ice is not static but a dynamic system, a frozen river in a constant state of (very slow) motion.

All morning we follow that river upstream. No previous mountaineering experience is required to walk on Aletsch, but we can only be here as part of a guided tour – partly for the glacier’s protection but mostly for our own. It’s an almost imperceptible climb, but the monotony of the trudge, and the tricks that the enormity of the whiteness plays with my sense of perspective, combine to make the journey unexpectedly gruelling. We stop briefly for lunch, freed from the rope, and eat bread and cheese in the midday sun on the edge of a crevasse.

At one point everyone jumps at a sudden, fearsome roar emanating from somewhere beneath our feet. This, says David, is simply chunks of ice shifting inside a crevasse, but local people knew these noises as arme Seelen (poor souls), evildoers whose souls were condemned to entombment within the glacier. “They live during the day in crevasses, at midnight they come out,” he says, smiling. “When they touch you, it means you are going to die.”

Eleven thousand years ago this glacier was so deep that only the tips of the mountains around us protruded from the ice. In the 17th century, during the cold snap known as the little ice age, its advance threatened destruction for farms in the Upper Rhône valley below. German-speaking Catholics from the village of Fiesch, where we caught the cable car this morning, began an annual pilgrimage to beg God to turn the glacier back. It might have taken 300 years, but today their prayers seem to have worked …

Since the late 19th century Aletsch has lost almost two miles of its length, and by 2100 it is predicted to shrink by eight miles more, reducing