In the southern part of Iceland is the national park of Skaftafell. On its territory there is a spur of the glacier Vatnajöküldl - glacier Skaftafetlsjökul with the famous ice cave.
Ice cave is a natural creation, which was formed as a result of the work of the glacier. The glacier for many centuries of work, made a layering on the frozen lagoon of Swinafelskel. Ice descended the slopes of the glacier, forming a cave. It looks amazingly beautiful and impressive.
Because of the high pressure of the mass, the ice displaced air from the solid layers, so the ice cave does not contain air bubbles in the walls. The absence of bubbles led to the fact that all light is absorbed. Thus, the ice cave shines from the inside, in blue and creates a feeling that it is lined with sapphires. But in blue, the cave does not always shine. In winter, long rains wash off the top layer.
The ice cave is generally unsafe. At any moment it can collapse. This is connected with the fact that the glacier is in constant motion. It is safely in it in the winter, when the ice hardens under the influence of frost and the probability of a collapse is quite small. In addition, during the winter you can hear the cracking of ice and have time to get out. What can not you say about the summer time. During this period, the cave walls become not so solid, and the movement of the ice does not create a sound. From the entrance, from 6 meters, the cave narrows less than a meter.
Source: http://etotam.com/?p=466
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