A quarter of a century since 9/11 – history’s most deadly terrorist attack – and we’re again seeing horrific scenes as even bigger towers crumble and crush all that lie in their shadow. These new collapses aren’t of human structures, they are of our high mountains and their glaciers, often described as the water towers of the world. But their demise is every bit as much a story of human folly as the fall of the Twin Towers.
What happens when you smash together white ice and snow, black rock and brown soil under intense pressure and hurl it a kilometre down a mountainside? Just as when you mix a number of colours together, you get grey and this was the colour of the pulverised debris that crashed down on the doomed village of Blatten in Switzerland as the Birch Glacier collapsed on Wednesday, 28th May, 2025. Ninety percent of the Blatten’s houses were buried, while the remaining dwellings were then drowned as the local river, the Lonza, rose, dammed by the debris mound. The 300 residents of the village had been evacuated days earlier as geologists had been monitoring the decaying glacier for years.
The collapse followed a mountain peak above the glacier, the Kleines Nesthorn, crumbling onto the Birch Glacier. The peak had suffered multiple landslips as rising temperatures had melted the ice that glued its rocks together, something being seen around the world in high mountain peaks. The debris from those landslips lay on top of the Birch Glacier that was itself suffering ice loss from global warming. The added pressure from the weight of landslip debris increased the pressure on the ice and water at the base of the glacier causing a higher rate of melting leading to a sudden catastrophic collapse of most of the glacier ice mass, hurtling some 3 million cubic meters of material down into the valley 900m below.
Because authorities had been closely monitoring the decaying ice river there were multiple cameras trained on the glacier when it collapsed at 3.24pm local time, giving the world a rarely witnessed account of a collapsing glacier.
Watching the video of explosive plumes of grey debris being thrown high out into the air as the landslide hit obstacles on its freight-train like passage down the mountain side, I couldn’t help but think of the grey ash plumes streaming out from the collapsing World Trade towers after the 9/11 terror attacks in New York in 2001. As with the glacier, the many colours of steel, concrete, glass, office furniture and human body parts was pulverised together under intense pressure to form an exploding cloud of grey, toxic dust.
The emotional response was also similar as I realised ‘this is not normal’, the world is a different place; skyscrapers and glaciers simply don’t collapse like this.
Slow then fast
While these were very different events, there are similarities worth keeping in mind. Both began with a disturbance loading down the upper levels of the structures (skyscraper and glacier). At a certain point, the loading overwhelmed the integrity of the structure and then they both collapsed in moments. The seemingly impossible had occurred, but once the collapse began it proceeded with blinding speed.
Possibly both situations serve as a metaphor for the changes we can expect in the coming years as the planet warms. First slow, then unstoppably fast.
Water of life
Though it’s not just collapsing glaciers burying human settlements we need to consider. Glaciers, and particularly Himalayan glaciers, provide critical water to nearly two billion people, and they are melting faster than ever before due to climate change.
And glacier loss is accelerating. 2025 saw a loss of over 400 gigatonnes of glacier ice, marking the sixth most negative year since records began in 1975. The past decade has seen a dramatic acceleration in ice loss, with annual losses nearly four times higher than those observed in the late 20th century.
Disasters not so natural
9/11 shook the world; it destroyed our certainty that the future was sure and safe. It led to the direct death of almost 3,000 people in the US and sparked a War on Terror that engulfed Afghanistan, Iraq and Syria, killing hundreds of thousands of people and shredding whole nations. It’s legacy still lies heavily on us today.
We think of these disasters as sudden events, coming from nowhere. However, pull back a little and it’s easy to see their antecedents were years, if not decades (indeed centuries), in the making. 9/11 arose from ideological fanaticism fuelled by long standing perceptions of injustice and inequality (inequities currently being magnified by climate disruption). The Birch Glacier collapse was the result of decades of global warming melting our mountain tops and destabilizing ice flows.
These were not Acts of God, they were outcomes of long-standing human myopia. And yet our responses to both disasters suggest we fail to see this distinction. Following 9/11 the response was a massive security clamp down to buttress and protect the status quo. Following the Birch Glacier collapse there were calls for better monitoring and early warning systems so similar collapses in the future would not cause too much disruption and loss of life. These responses were to the symptoms, not the underlying causes.
And, because the underlying causes have not been addressed, we should expect similar catastrophes in the days, months and years ahead. Indeed, as the 25th anniversary of 9/11 comes up we have just seen another collapse of one the world’s greatest water towers. Days ago, on the 26 August, the horrible news came in of a Himalayan glacier collapse in Nepal/Tibet in which an area of around one square kilometre of ice and rock collapsed into the valley below sending a tidal wave of unstoppable debris, water and ice downstream. Unlike the Birch Glacier collapse, no-one was monitoring this part of the world and the local Nepalese population was caught unawares resulting in the death of thousands of people and the mass destruction of towns and infrastructure.
No-one that I am aware of has connected the Nepalese disaster to the 9/11 attack, and clearly they are very different types of disasters. However, I think a little reflection on the context and causes of these catastrophes wouldn’t be amiss. They both have direct human causes with pressures slowly building over time, they both demonstrate that humans are not in control, and they both suggest our current choices on how we deal with a rapidly changing world are short sighted and inadequate given the scale of the challenges confronting us.
A Sus Bites Postscript: Dear Reader, this is my first Sustainability Bite blog for some time. As explained earlier this year, I’ve been writing a book on sustainability and democracy with my colleague Quentin Grafton, and it has absorbed most of my free time. We handed our draft into Cambridge University Press last week so I’m hoping I’ll be more productive on the blog front in coming months. Many of the new blogs I’m planning will be inspired by stories appearing in our new book (current title: The Great Disconnect). Indeed, this comparison between 9/11 and glacier collapse appeared in an earlier draft of the book, and the themes of injustice, equity and sustainability are central themes of the thesis we present.
Image: On reflection: The cascading reflecting pools at the National September 11 Memorial in New York City. The footprint of this memorial mark out where the World Trade Centre buildings stood a quarter of a century ago. (Image by Jens Junge from Pixabay)
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