How to explain these strange formations observed on a frozen lake? ❄️

On the frozen waters of Lac des Rousses, in the Jura, an unusual spectacle captivated walkers. Snow and ice disks, resembling pancakes, emerged on the surface, offering an almost supernatural vision. This phenomenon, rare in France, intrigues with its beauty and complexity.


These formations, called "pancake snow," result from very specific weather conditions. Intense cold, a completely frozen lake, and a light wind are enough for snow to accumulate around small obstacles. Gradually, these mounds become covered with frost, taking on a characteristic circular shape.

Lac des Rousses, located at an altitude of over 1,000 meters (3,280 feet), is a prime location for this kind of phenomenon. Its microclimate, marked by freezing nights and high humidity, promotes the rapid crystallization of snow. These conditions, combined with a moderate wind, allow the creation of these ephemeral disks.

Science explains this process in several steps. Light snow first clings to fragments of ice or twigs. Then, frost covers these mounds, transforming them into disks. Finally, the wind shapes them, giving them a pancake-like appearance. This phenomenon, rare in France, is more common in other regions.

In Canada, the frozen lakes of Alberta and Saskatchewan are often the stage for these formations. In Scandinavia, frozen fjords and lakes also offer this spectacle. In Russia, the polar nights of Siberia sometimes allow the appearance of these ice disks.


To observe this phenomenon, it is advisable to go to high-altitude areas, such as mountain lakes. Clear nights, with temperatures below -5 °C (23 °F), are ideal. Dawn is often the best time to admire these formations, before the sun begins to melt them.

This natural spectacle, although brief, reminds us of the beauty and complexity of our environment. It attracts curious onlookers and photographers every year, eager to capture these unique moments. Lac des Rousses, with its particular conditions, remains a privileged location in France to witness this phenomenon.