A fisherman checks his fishing nets at dawn; a shopkeeper opens his store’s shutter. It is just any other ordinary day for them. The river trickles and gurgles, a familiar background sound for both. Neither suspects what’s heading towards them. A train of events that, unbeknownst to them, may have been set off months before by unstable rocks further upstream.
To see how this happens, we have to rewind. Imagine a Rube Goldberg Machine, an overcomplicated contraption that uses a long chain reaction to perform a simple task, where a tipped-over book pushes a ball into a bucket, which is attached to a string that, when pulled, turns on a light switch. The Rube Goldberg Machine we’re going to look at today wasn’t made by a human; it was made by nature. And scientists call it a Cascading Hazard.
Gear 1: A Weakened Slope
Mountains may look indestructible but if the internal strength of it’s soil or rock is overcome by heavy rain, gravity, earthquakes, thawing glaciers/permafrost. And all that loosened rock will start falling.
Gears 2 and 3: The slide and the cork
When the loosened rock lets go, it slides down the slope and falls into the valley below. And if a river runs there, the debris clogs it like a cork stopper in a bottle. The river’s water starts pooling behind it in a lake. But no one can tell how long the cork will keep the water bottled behind it.
Gear 4: The breach
Eventually the water finds a way through the cork. And all the water behind it explodes out in a flood. As the flood tears downstream it picks up sediment and rocks, and destroys bridges, roads and homes in its path.
Each gear makes sense on its own but together they create a tremendous disaster no single event could have done alone. Now let’s take a look at this machine at work in different regions.
Take a look at the Himalayas, Karakoram, and Hindukush. On January 4th, 2010, a landslide occurred in the Hunza Valley. The initial disaster buried the village of Attabad, heartbreakingly destroying 26 homes and killing 20 people. But that wasn’t the end of it. That landslide also blocked the Hunza River. That blockage created the Attabad Lake. A lake that remains a threat to this day for villages downstream who are vulnerable to flooding if earthquakes, or heavy rainfall breach the debris.
Moving towards the Alps. On May 28, 2025, an avalanche from the Birch Glacier buried the Swiss village of Blatten. The avalanche also blocked the river Lonza, causing it to flood. The trigger for this was rockfall. Heavy rock from a crumbling mountain peak fell onto the glacier and pushed it out of balance. This disaster destroyed 90% of the village.
Not every hazard has happened yet. In Alaska’s Barry Arm fjord, the retreating Barry Glacier has left land which is unstable. And scientists say if that land fails, the slide could trigger a huge tsunami with waves hundreds of feet tall. This has happened before in 1985 at Lituya Bay which sent waves of more than 1,700 ft.
The good news is: This Rube Goldberg Machine can be stopped at any step, if someone is watching.
In the Swiss village of Blatten, being vigilant worked. When the slope’s movements sped up, about 300 people and livestock were moved out days before the collapse. This evacuation helped save all these lives.
At Barry Arm, Alaska’s Division of Geological and Geophysical Surveys is monitoring the slope after satellite data showed risks. Tools like slope monitoring, lake level sensors, and early warning systems may not stop a mountain from moving. But they can give downstream communities precious time, which could save their lives.
So back to the fisherman and his nets. Whether the flood becomes a tragedy or a close call depends on how early someone notices the gears turning.
References
- NASA Landslide in North Pakistan : https://science.nasa.gov/earth/earth-observatory/landslide-lake-in-northwest-pakistan-43175/
- NASA Glacier Collapse Buries Swiss Village : https://science.nasa.gov/earth/earth-observatory/glacier-collapse-buries-swiss-village-154387/
- State of Alaska Barry Arm Landslide and Tsunami Hazard: https://dggs.alaska.gov/hazards/barry-arm-landslide.html
- Cascading land surface hazards as a nexus in the Earth system: https://www.usgs.gov/publications/cascading-land-surface-hazards-a-nexus-earth-system
Also Read: Water Security After Floods: A Look Into Consequences, Remediation, and Mitigation
Muntaha Uzair is a top scorer for Scientia’s Science Writing Internship Cohort Five. She studies in High School Islamabad.
