school energy&environment

Studying ice caves

The entire glacier body moves continuously downstream and in this movement it drags whatever is on its surface and inside. Therefore also the ice cave systems move downward together with the glacier in which they have formed. By studying the mechanisms by which these cavities form, it has been possible to observe that a new sinkhole forms every year in the same point of the glacier, above a fixed point of the substratum. It is as if in that point there were particular conditions, due, for example, to the characteristics of the substratum, that determine the formation of a moulin in the ice that is in that point at that time. The same occurs in the case of whirlpools and eddies in the current of a stream of water: the shape of the whirlpool is always the same, and also the point in which it forms, but the water that forms the whirlpool is continually replaced. For this reason, even though they vary continuosly, glacial caves are stable structures inside a glacier. The distance separating a new sinkhole from the one that formed the previous year, therefore, is equal to the speed of the glacier’s downward movement: measuring the distance between aligned moulins is therefore an excellent and rapid system to evaluate the speed of a glacier. And by observing aligned moulins from the top of the mountain to the valley, it has been observed that the speed is not the same for the entire glacier, but it is as if within the body of the glacier there are areas flowing with different flows, that may be more or less rapid: the distances between moulins belonging to the same alignment enable a “visual” evaluation, and do not require complex measurements, the areas that are faster are where the moulins are further apart one from the other, and the slower areas are where the moulins are to be found closer together.