There is this lake in Eastern Finland. It freezes in the early winter and stays frozen until the end of March. It is a large lake and when the winter starts and the temperature drops a thin layer of ice begins to form starting from the shorelines and moving slowly towards the center. Then it can snow and the thin layer of ice gets covered by a white mantle which hides how thick the ice really is. But this is a large lake. Water moves. There are streams and currents hidden under the ice. In the silence of the the winter one can easily hear the sudden sound of cracks or a strange noise as if huge bubbles would try to break and escape the hard ice surface that will cover them until the spring.