When lakes freeze up

The lakes in the Dolomites are irresistible even in winter, when their surfaces freeze and they are transformed into sheets of ice. And, if the layer of ice is thick enough to withstand our weight, then we can even walk on them (but be careful not to slip and, above all, before doing so, make sure that the ice is thick enough!) or speed across them on ice skates.

As cold as it may be, however, no lake freezes up completely. In fact, the sheets of ice that form on the surface shelter the water below from the cold, therefore it remains in its liquid form, allowing plants and aquatic animals to survive the winter.

This miracle of nature is due to the peculiar behaviour of water molecules that form the upper layer of the lake. When winter arrives, the water on the surface, which is most exposed to low external temperatures, cools down first. Usually, when in the water is colder, it also becomes denser and it consequently tends to slide towards the bottom. This in fact is what happens until temperatures do not fall below 4°C: as the water on the surface cools, it slides to the bottom and pushes up the warmer waters below, which in turn inevitably cool down and sink down, in a cycle that continues until all the lake reaches a uniform temperature.