Thousands of giant rocks scattered across Switzerland have puzzled people for centuries.
Many of these huge boulders are sitting far from the mountains where they were originally formed.
Now, researchers have recreated their remarkable journey for the first time, showing how glaciers carried millions of rocks across the Alps about 24,000 years ago.
The study, led by researchers at the University of Lausanne (UNIL) in Switzerland, used a powerful computer simulation to trace the movement of rocks during the last Ice Age. Their findings were published in the journal Earth Surface Dynamics.
Around 24,000 years ago, the Alps looked very different from today. Thick sheets of ice covered much of the mountain range.
Massive glaciers slowly flowed down from the high peaks into the valleys, acting like giant bulldozers.
As they moved, they scraped away rock, carried enormous boulders over long distances, carved deep valleys, and shaped the basins that later became many of Switzerland’s famous lakes.
These glaciers played a major role in creating the landscape we see today. Features such as the terraces beneath the city of Lausanne and the basin that became Lake Geneva were all influenced by the movement of ancient ice.
Although geologists have long known where many of these giant rocks originally came from, it has been much harder to understand the exact routes they followed. Some rocks ended up in places that seemed almost impossible to explain.
To solve this mystery, the research team developed the first computer model capable of tracking the movement of rocks across the entire Alpine region. Instead of following just a few boulders, the simulation traced millions of rocks and pieces of sediment as they traveled with the glaciers.
The researchers fed the model with detailed information about the Alps, including the shape of the mountains, the movement of the glaciers, and climate conditions during the Ice Age.
The simulation then calculated how the ice carried rocks downhill, across valleys, and even over mountain passes before leaving them where they are found today.
The project also produced a catalog that helps scientists identify where rocks and sediments in different parts of the Alps likely came from. This information will help geologists studying ancient glaciers, river systems, and the formation of lakes and valleys.
The research became possible thanks to a powerful computer model called IGM, developed at the University of Lausanne. One reason the model works so well is the use of modern graphics processing units, or GPUs.
These computer chips were originally designed to create realistic graphics for video games, but they are now widely used in scientific research because they can perform millions of calculations at the same time.
Using GPUs has made the glacier model up to 100 times faster than older versions. This allows scientists to simulate complicated natural processes that were previously far too slow to calculate.
Researchers hope the model will answer many long-standing questions about how landscapes form and change over thousands of years.
It can also be used to study glaciers under future climate conditions, helping scientists better understand how melting ice may continue to reshape mountain regions around the world.
