Peru is home to 75% of the world’s tropical glaciers. On the Salkantay trek, our guide explained what they mean and the kind of disasters they can trigger.
The story of Peru's tropical glaciers
As you hike up toward Salkantay Pass, you pass within a few hundred meters of one of the most impressive glaciers in the tropical Andes. Our guide then explains what these masses of ice really mean for the people who live below them. A source of life. And sometimes, of death.
75% of the world's tropical glaciers in Peru
Tropical glaciers are glaciers found near the equator, in an area where average temperatures are much higher than in polar regions.
Peru holds 75 % of all the tropical glaciers on the planet. That figure is hard to picture, but it says a lot about this country's unique geography.
The world's largest tropical glacier used to be Quelccaya, in the Cusco region, with an area of 70 km². I say "used to be" because its melting, documented for several decades, has significantly reduced its size. Between 2000 and 2002, a ski resort was even built there before being quickly abandoned, notably because of environmental regulations and the acceleration of glacial retreat.
The Salkantay itself is ringed by imposing glaciers. Its namesake pass at 4 630 meters marks the divide between the eastern Andes and the Amazon Basin, and the glaciers around it directly feed the rivers that irrigate the valleys below.
Vital springs at 4,000 meters
For the communities living between 3,500 and 4,000 meters above sea level in the Andean valleys, glaciers are not just scenery. They are their source of drinking water and what makes farming possible.
Peru has only two seasons: the rainy season and the dry season. During the dry season, it is the glaciers that feed the rivers, irrigation systems, and natural reservoirs. Without them, crops fail, livestock die, and communities have to move.
It is this vital dependence that explains the veneration of the Apus in Andean cosmology. A mountain that has nourished an entire valley for millennia is not just a geographic backdrop: it is an entity to which life itself is owed.
When glaciers turn into disasters: huaycos
A Huayco (pronounced "Wayco") is what we would call in French a "mudflow" or an "ice-and-rock tsunami." It's the most feared phenomenon in the Andean valleys.
The principle is simple but devastating: a chunk of glacier breaks away from the mountain face, falls into a high-altitude lagoon or stream, and triggers a shock wave that makes the water overflow, sweeping away everything in the valley below. Houses, crops, roads, infrastructure: a Huayco leaves nothing behind.
Peru is one of the countries in the world that records the highest number of natural disasters of this kind. The reason is geological: the country lies on the Pacific Ring of Fire, at the collision point of the Nazca Plate and the South American Plate. These two plates are constantly rubbing against each other, causing 85% of the earthquakes in this area. Every quake can trigger Huaycos in the glacial valleys.
On 31 May 1970, a magnitude 7.9 earthquake struck northern Peru. What followed was one of the deadliest natural disasters of the 20th century.
The earthquake caused part of the North Glacier of Huascarán, the highest peak in Peru at 6,768 meters, to break away. Millions of cubic meters of ice, rock, and mud came loose and rushed down the mountain at an estimated speed of between 200 and 300 km/h.
The town of Yungay, with its 69,000 inhabitants, lies in the valley below. A natural wall prevents residents from seeing what's coming. In less than four minutes, the town is completely buried under several meters of mud and rock. The only survivors from the town center are a few residents who were on a slightly elevated hill, and a handful of children who were taking part in sports activities outside the town that day.
Today, the Yungay that exists today is a rebuilt town next to the original site. The former town center is a national cemetery. You can still see the top of the church bell tower sticking out of the mud.
To go further: The town of Yungay and the Campo Santo marking the location of the old city are accessible from Huaraz, about a 1-hour drive away. It is a deeply moving place of remembrance, often left out of standard tourist routes.
Recent events in the Salkantay region
The Salkantay region itself has seen several major events in recent decades.
In 1993, part of the South Salkantay glacier broke off and fell into the Aobamba River, causing it to overflow and sweeping away the town of Santa Teresa downstream.
In 2002, another block fell into a tributary of the same river, striking the Machu Picchu hydroelectric plant. Half of the infrastructure was torn away, and above all, the train tracks linking Cusco to Aguas Calientes, the main commercial route for the region's fruit and coffee, were never rebuilt.
In March 2020, right at the start of the worldwide lockdown, a whole section of the glacier broke away on the side opposite the valley where the trek passes. The river in the Lucmabamba Valley rose by 180 meters in just a few hours, sweeping away every house, crop, path, and road in the valley. The local community was cut off from the world for nine months, supplied only by army helicopters. Two years of pandemic with no tourism followed, leaving residents with no resources to rebuild.
If you do the Salkantay trek, your guide will show you the traces of the 2020 event on the valley slopes. These marks are a reminder that the mountain, as beautiful as it is, is still an environment that deserves deep respect.
Accelerated melting and its consequences
Andean glaciers are melting at a documented and worrying rate. This melt has two main consequences that seem contradictory at first.
In the short term, it increases river flow, which can temporarily benefit agriculture. But in the long term, once the glaciers have retreated enough, the rivers will run dry in the dry season, depriving local communities of their main water source.
Melting also releases Inca mummies and other archaeological artifacts preserved in the ice for centuries. These finds are scientifically valuable, but they come with the gradual destruction of an irreplaceable natural heritage.
Finally, glacier melt naturally raises the risk of Huaycos: less stable ice masses on more exposed slopes, glacial lagoons that fill up faster, and downstream valleys whose infrastructure is not designed for floods of this magnitude.
