The great silent glow and the singing lake

Those who were lucky enough to be in the Upper Engadine in the days before Christmas were not only able to take beautiful walks along the shores of the Engadine lakes in glorious weather, but also witnessed a rare natural phenomenon. Overnight, Lake Sils was covered with a layer of the rare black ice. Beforehand, it had been freezing cold for a long time and it had not snowed. Thus, the initially wafer-thin skin of ice on the lake became a coherent black sheet of ice. To be precise, the ice was not “black” of course, but because it had formed in clear weather, it now lay mirror-smooth and amazingly transparent in front of us, and through the crystal-clear surface one could see into the dark depths of the water.
  It was getting towards evening, and the unique light conditions in the Upper Engadine – this great silent glow – brought with it a great calm. It was broken by strange sounds that spread over the ice. A murmur, hissing, gurgling, then a sudden bang was heard. After about three hours it was over. But only until the next morning, when the sound spectacle begins again about two hours before sunrise. A natural phenomenon that only occurs with black ice.

Large temperature differences and small cracks

The reason for the “singing lakes” is tension in the ice, because like any other material it reacts to large temperature differences. When the sun shines, the large black ice surface provides ideal conditions for them to form. If it gets warmer, the upper side of the ice expands, if it gets colder, it contracts. The lower side of the ice, on the other hand, remains rigid and hardly changes. Now the ice “works”. At the lower edge, small cracks form, which run through the ice surface like a spider’s web, and which only open up a little at exceptionally low temperatures. The cracking of these cracks causes the “singing”: The sound propagates at great speed along these tension cracks in the ice sheet, which can easily be several hundred metres long. It is faster in the ice than in the air, and the faster, the higher the sound to the human ear. If the ice is covered with snow, it acts like a sound absorber and the “icy” music disappears. This is the secret of the “singing lake”, which could well lead to mystical explanations.

Flowers of ice

But the cracks also lead to another fairy-tale-like phenomenon to be admired: the hoarfrost ice flowers – that, too, a rather rare phenomenon on the Upper Engadine lakes. There is also a scientific explanation for their formation. The ingredients are the sun in the steel-blue winter sky and the resulting large evaporation over the icy lake. When it gets cooler after sunset, the air’s capacity to absorb water vapour decreases. The air above the ice is now quite humid. With the cold temperatures at night, it condenses. In the morning, the landscape looks like it is covered in sugar from the hoarfrost that has formed. The small piles of ice crystals with their faces and edges, which have formed on the surface of the ice from the lake water, form the nuclei on which beautiful ice flowers can “grow” thanks to the moisture in the air. They are often found in whole groups or flocks. How they form exactly depends mainly on humidity, temperature and wind. If the crevices are moistened by seawater, diverse, enchanting formations also grow along them. Sometimes a real sea of ice flowers forms on the ice.

From the depths of the lake bed

But these are not the only phenomena in the black ice that invite you to linger and investigate. In some places in the still young ice cover, columns become visible that are reminiscent of the thought bubbles in a comic strip. They are formed by methane gas bubbles that rise from the bottom of the lake and freeze in the process.
  Anyone who has had to suffer frost damage from burst water pipes gets to see a vivid example of the expansion of the ice here on the shore of the frozen lake, because after several days of exposure to the sun, broken layers of ice have slid over each other to form a confused but decorative jumble of glassy debris stripes.
  So, the black ice became a good subject for the camera and stimulated reflection and investigation, just like the ice flowers, the gas bubbles and the many other “wonders” that nature can produce.
  There is something very relaxing about being in nature and observing what fascinating phenomena are possible. Whoever does this with their children is doing them a labour of love. Not only do they learn to observe attentively and draw conclusions, but they also sharpen their senses and gain more inner peace in an everyday life that today is often dominated by “action” and fast-moving “events”. In doing so, they strengthen their emotional connection to nature and to the land in which they live. •
 

Firnelicht

Wie pocht’ das Herz mir in der Brust
Trotz meiner jungen Wanderlust,
Wann, heimgewendet, ich erschaut
Die Schneegebirge, süss umblaut,
Das grosse stille Leuchten!

Ich atmet eilig, wie auf Raub,
Der Märkte Dunst, der Städte Staub.
Ich sah den Kampf. Was sagest du,
Mein reines Firnelicht, dazu,
Du grosses stilles Leuchten?

Nie prahlt ich mit der Heimat noch
Und liebe sie von Herzen doch!
In meinem Wesen und Gedicht
Allüberall ist Firnelicht,
Das grosse stille Leuchten.

Was kann ich für die Heimat tun,
Bevor ich geh im Grabe ruhn?
Was geb ich, das dem Tod entflieht?
Vielleicht ein Wort, vielleicht ein Lied,
Ein kleines stilles Leuchten!

Conrad Ferdinand Meyer
(* 11.10.1825, † 28.11.1898)