Journey to the heart of a glacier

Into the deep

The Plaine Morte (‘dead plain’) Glacier is as untouched as its name suggests. But this winter a group of adventurers decided to go right to its heart. Written for the Tages-Anzeiger, this in-depth exploration of what they discovered, with spectacular imagery and emotions, is the result.

The horizon is rarely a straight line in Switzerland. The terrain is usually too mountainous, and when there is no mountain in the way, there is invariably a chimney or a pylon blocking the view. For this reason, the panorama from the Plaine Morte, the biggest plateau glacier in the Alps, comes as something of a surprise. Looking North, the Gletscherhorn mountain towers to the right; the Wildstrubel to the left; and in the midst of it all a sharp clear line cuts between blue and white, between sky and snow. Such clear and sharp colours can usually only be found at the Poles.

At an altitude of about 2,700 metres, the 200-metre-thick ice lies in a gigantic basin high above the valleys of Valais and the Bernese Oberland. There is hardly any life up here; the vastness and wind ruffling the surface of the snow are about the only forces to be found. If it sounds eternal, far from it: by the end of the century, the glacier will most probably be completely gone. Glaciological models show that by 2090, there won’t be a piece of ice left. Even now, we can see redundant steel cables and poles lying on the rocky slope: the sad leftovers of a ski lift forced to close due to the glacial retreat.

The dead-ice holds many mysteries, and nobody knows them better than Fred Bétrisey und Hervé Krummenacher. Considering the vastness and the monotony above ground, their reports are hard to believe. A breath-taking underworld is supposed to be hiding underneath the snow and ice; so beautiful that all fear is gone once you set foot in it. Once it has drawn you in, they say, you just want to go deeper and deeper as if you never wanted to see daylight again. 

That glaciers have their own, hidden, lives has been known for a long time. In summer, for example, we can see melt water disappearing in deep holes, but nobody really knows what happens next. The fact that the water eventually flows out at the end of the glacier suggests that there must be a well-connected canal system somewhere down there. Fred and Hervé want to do what has never yet been done: they want to inspect the whole labyrinth, in all its dimensions. And if it’s obvious that these two big men will move a lot less graciously than the tiny glacial streams, they are determined not leave a stone unturned in exploring the underworld. We have the chance to go with them.

The beginning of winter this year is cold and dry – ideal conditions to go for a hike inside a glacier. Indeed, the expedition starts on a promising note when we arrive, just before Christmas, at the moulin [circular shaft in a glacier] in the middle of the plain. In summer, when the accumulated water thunders down into the valleys, this would be the ideal place for a murderer to make a dead body disappear forever. In the winter, however, the water runs dry. On an earlier exploration, Fred and Hervé had already been as far as 150 metres below the surface. “At first it’s a vertical drop and then you enter a narrow corridor on the side…” Fred explained when we were at his house just above Sion a few days earlier. He took a piece of paper with some math problems of his 11-year-old daughter, turned it over and drew a sketch of the hole; and now, impossibly, we are here, abseiling into it, one by one.

Water thunders down here during the summers. For a short period in winter, it is possible to enter this moulin.

The entry into the horizontal corridors is tiny. Getting through demands some digging.

After about 50 metres, we reach snowy ground. Hervé instructs that we remain tied into the rope at all times; this could be just a thin snow bridge leading across the vertical gorge and it could collapse at any time. “It looks different every year,” Fred says, looking up to another gigantic snow bridge towering high above us. “If it tumbles down, we’ll be trapped. It’s cold though and it seems pretty stable,” he says confidently, before disappearing into a niche and starting to dig.

“If there was a bit more snow, we wouldn’t stand a chance,“ Fred calls out of the darkness. His voice sounds muffled. We follow him. Our eyes take some time to become used to the new surroundings. We have just entered a completely new world: we are surrounded by blue ice, which is as hard as concrete and reflects the shining lights of our headlamps. Snow crystals sparkle all around us. The ground is as flat as a pancake, ice cracks underneath our crampons and our sounds echo through the labyrinths.

Just like a piece of wood, an odd-looking snow layer is wedged between the walls of the corridor. "This is a leftover of the snow-water mix that still runs here at the beginning of winter,” Hervé explains. During an earlier excursion, he and Fred put on their wetsuits and swam through the corridors in exactly this soup. After having crawled through underneath the relic, the terrain allows us to walk upright again. Here the corridor is a few metres high suggesting a curve of about 180 degrees. In the light of our headlamps, we can see that the ice has been shaped into a pillar.

In a later conversation, the glaciologist Matthias Huss, who lectures at the Swiss Federal Institute of Technology in Zurich and at Fribourg University, explains that a so-called ‘cut-and-closure’ process could have created this pillar. This phenomenon is well known, especially in Arctic glaciers: running glacial water cuts deep canyons into the ice, which usually close up again on the surface. Underground, however, they remain open. This means that underground canyons, invisible from above, could permeate the whole glacier. Husch has been conducting his research on the Plaine Morte Glacier for many years. He has never been inside, however, and is surprised to hear about the horizontal corridors. “Up until now, we have always assumed that the water goes through the moulin and then drops directly onto the rocks.” He is convinced that science will benefit hugely from observations made inside the glacier. “This is the only way to find out whether our theory has been right or whether we have to revise it.”

The cut-and-closure-process at the entry could be an explanation for how this structure was created. Up until now, this process has mainly been observed in Arctic glaciers.

Walking inside a glacier was considered taboo for a long time – it was simply too dangerous. Today, still, it is not exactly a popular activity. Polish researchers made their first observations in 1990, when they explored the inside of glaciers in Spitzbergen [Norway] that posed a manageable risk. The climate of the Arctic winter is ideal; the persistent cold penetrates into the glacier and makes everything freeze. The winters in latitudes around Switzerland are a lot less predictable: temperature fluctuations can happen even at high altitudes, resulting in the accumulation of glacial water. This is part of the reason why there has been very little ice cave exploration in the Alps.

After these first explorations, other international teams followed suit and started to dig into glaciers in the Arctic and the Himalayas. But no matter how spectacular their observations were, they met with scant interest from the world of science. Instead, ice cave research was regarded an adventure. The Scottish glaciologist Doug Benn is a man who certainly does not agree with this. He has studied glacial lakes in the Himalayas for many years and has always wondered why they continually drained. Benn found the answers to his questions underground, when he realised that the water was doing exactly what it was doing inside rocks: making its way through the weak points of the glacier. However, while it takes millions of years inside a rock, it happens relatively quickly in the ice. In the space of a single summer, drainage channels can form, before closing again in the winter.

Of course, many questions remain, but finding the answers is becoming an increasingly pressing issue. If glaciers continue to melt in the coming years, immense quantities of water will be released. Bursting glacial lakes and tidal waves thundering down into valleys below can pose a threat to entire regions. “Entering a glacier is the only way to understand these complex processes. It gives us the opportunity to discard and reconsider simplified theories of the water supply,” Benn says. “Most glaciologists still consider it far too crazy, even though most accidents happen with tourists walking along the snout of a glacier, where masses of ice come thundering down, especially in the summer.” In winter, the ice is relatively stable.

Vertical shafts lead deep inside the glacier. At one point, there is rock, but nobody has gone that far yet.

Suddenly, we see a fly frozen in the ground. This discovery is not only a reminder that once a glacier has captured something, it does not give it away readily; it is also an indication that the flat ground we are standing on is actually frozen stagnant water. We are now 70 metres below the surface. The lower we go, the higher the tension. What would happen if – for whatever reason – one of the narrow corridors behind us collapsed is unthinkable. We would most likely end up like the fly. However, the ice is as bombproof as a brick wall, and it does not give the impression that it wants to trap us. “The biggest danger is the water anyway,” Hervé says. He seems to notice that our silence is not solely down to fatigue. “You can also find water down here in winter. We are lucky this year: due to the dry autumn, the water has trickled farther down. A sudden rise in the water level would be dangerous.” There is no indication that this could happen. It seems as if everything stands still: the water, the ice, time. If we didn’t know any better, we would think this was some form of eternity.

This is where we stop our first excursion, even though we are still far from the lowest point. We could continue for another 150 metres over some more stages. Neither Fred nor Hervé have ever been beyond this point, which means it would also be new ground for them. However, the long return leg would keep us busy for the rest of the day, and when we get back to the surface, the sun has long disappeared behind the mountains. The flat glows in the faint light of the stars.

Over tuna pasta, Fred and Hervé tell us about their plan for the following day: they want to look for the entry point on the eastern end of the glacier, where the water has cut a gorge into the ice. “The outflow must be gigantic,” Fred says, explaining that in summer a gigantic glacial lake, the Lac des Faverges, usually lies there. Come autumn, it suddenly vanishes when around two cubic metres of water gushes through the glacier and only reappears when it flows into the Simmental Valley. “It is as if someone pulls the plug of a gigantic bathtub.” The tranquil Simme turns into a raging river and, with the increasing size of the lake, the threat of a devastating tidal wave gets bigger each year: it has actually tripled in size over the past five years. And because the level of the glacier has dropped, the lake can no longer drain into Valais, across the ridge. The creeks there have dried up and all the water now ends up in the Bernese Oberland. Since 2011, the Lac des Faverges has been under close surveillance, so that the population can be warned in case of bursting.

Hervé and Fred are convinced that – at least at times – the corridors must be connected throughout the whole glacier; otherwise, the lake could not drain. The underground canal system expands across 3.5 horizontal kilometres and 250 vertical metres and exploring this gigantic space has long been dream of theirs. Whether or not they can make it reality remains to be seen. “You would have to do it wearing a complete diving suit because of the water level,” Hervé says. This means that from a certain depth onwards, it would probably feel like being inside the sinking Titanic, with all the corridors filled with water. We contemplate this for a little while until the cold drives us into our sleeping bags.

It’s minus 25 degrees. It’s lonely and completely silent. And it’s hard to believe that all this will disappear in the coming decades.

The Plaine Morte Glacier has retreated more than any other glacier in the Alps, even though it was doing relatively well between 1960 and 2002. Then, the amount of ice in the winter was almost identical to the amount of melt water in the summer. However, since the turn of the millennium, there has been a rapid change and there has been less and less snow on the glacier during the summer. The rule of thumb in glaciology is that in order to keep the natural balance of a glacier, at least two thirds of the icy surface need to be covered in snow throughout the year. Over the past four years, the Plaine Morte was completely bare by the end of summer. Masses of ice are laid out like a dead body waiting for an open-air burial, while vultures circle above, wearing the dress of climate change.

The lake basin is dry. The trough turns into a gorge.

An ice wall marks the end. What is beneath it?

The following day, we step into the empty lake basin. Initially flat, the trough ends up in a gorge, which has cut itself deep into the ice. The ground is covered in snow, which makes walking comfortable; however, it is also a bit disconcerting, as we have no idea what is beneath us. We are roped together, getting closer to the end: an immense wall of ice towers above the arches, which looks like the entry portal to a tunnel. This must be the drain of the lake. In summer, millions of litres of water thunder down here on their journey through the glacier. Glaciologists assume that this underground drainage system recreates itself every year. In winter, it is crushed by the weight of the ice; in summer, it melts again. As soon as the canal system has tapped into the lake, it all happens very quickly: the canals are widened by the melting water as well as by friction, and the amount of water swells significantly within a few hours.

In the course of the summer, the Lac des Faverges fills up with meltwater. Glaciologists assume that the drainage is recreated each year. As soon as an exit point is created, the water drains quickly – up to 20 cubic metres per second have been measured.

end of infobox

We arrive at the ice wall, but we are disappointed to see that the entry is full of snow. There is not even the tiniest crack and no point in digging. Aerial pictures have shown that the course of the gorge is similar to a trouser-zipper: at the start, wide open, but then reduced to a tiny crack in the ice before finally disappearing completely. The pictures also show three holes in a row, which seem to indicate the course. Could these be moulins that end up in the underground canal system? We climb back up, and indeed, we find one of the holes. However, will there be less snow? We abseil down again.

Once again, we descend vertically into the depths of the glacier and hit snowy ground. Suddenly, we see something that makes our hearts leap. At the lowest point, we find icicles hanging above a dark hole with a diameter of about one metre. Dark holes are good. The darker, the better. It must lead somewhere. We fix a rope and crawl underneath the icicles. We get a first glimpse behind the curtain. Our sounds of excitement echo powerfully throughout the maze. This is only one indication of the vastness of the space we are in; our headlamps also fail to find latch onto any sign of an end.

A narrow but high shaft leads into the darkness. We are surprised to see that it gets brighter after a while. Faint blue light shines in from above. High above us, we can see something that looks like a round lid, letting some daylight in at the side. Could this be a moulin, covered over by snow on the surface? Is this what the snowy ground we walk on looks like from below? The fact that daylight gets in makes us believe that it is anything but solid. We call it the 'UFO lid' (apparently, this is what a UFO looks like from below) and hope that it will not come crashing down on us.

We have reached the water. We carefully move along the ice. Ice floes are swimming in the corridor.

Below our feet, we encounter another problem. The shaft ends and flat icy ground opens in front of us. After only two steps, it collapses. We start sinking in and quickly rush back onto solid ground. There it is: the water that does not freeze inside the glacier throughout the year. Alpine glaciers have a stable temperature of about zero degrees inside. It is different in the so-called ‘cold glaciers’ in the Arctic, where temperatures can drop to below zero. In the Alps, however, the winter cold only enters the top 10 metres. Farther down below, ice and water can coexist at any time.

Progress becomes cumbersome: we fix a rope on the sidewall and move carefully along it, inch by inch. Every so often, we pass big chunks of ice in the corridor and we carefully test their load-bearing capacities. Sometimes they offer solid ground.

Finally, we reach a space as big as a chapel. A small lake appears in front of us. Far above, we can see the light shining through the UFO lid. We are probably the first people ever to enter this space. On the walls, we can see fragments of ice plates indicating that the water level must have been much higher not too long ago. Some of these ice plates are as big as tables and are towering menacingly above us. We wonder whether our combined body temperature could generate enough heat to make them tumble down. We decide not to hang around too long.

At the end of the hall, we can see a continuation of the tunnel. The corridor disappears into the water. “Next time, we should bring wetsuits,” Hervé says to Fred. They are serious. We can sense that they feel at home down here. No adversity would make them give up on their dream. We, however, have reached the end. And who knows what it will look like next year…

Idea, concept and text:

Dominik Osswald

Programming and storytelling:

Kaspar Manz and Marc Brupbacher, interactive team

Photography, 360°‑panoramas:

Urs Wyss, Christian Mülhauser
Olivier Christe

Drone pictures

Christian Mülhauser


Dominik Osswald
Christian Mülhauser
Olivier Christe


Pierre Tschopp
Ursula Ritter
Geotest monitors the Lac des Faverges and supplied us with data for the 2nd animation


Jürg Candrian

Advice 360°‑picture production:

Janina Woods, Sebastian Tobler 
ateo GmbH

Gear sponsors:

Bächli Bergsport

Thanks to:

Frédéric Bétrisey
Hervé Krummenacher
Matthias Huss, Glaziologe ETH und Uni Fribourg
Kathrin Naegeli, Uni Fribourg
Daniel Tobler, Geotest
Bergbahnen Crans-Montana

swissinfo Production

Luca Schüpbach
Marcel Stauffer