Ice caves are temporary structures that appear at the edge of glaciers. They look amazingly beautiful from the inside. This particular cave is located on the frozen lagoon of the Svínafellsjökull glacier in Skaftafell, Iceland.
The centuries old ice coming down the slopes of Öræfajökull via Svínafellsjökull glacier has metamorphosed into highly pressurized glacier ice that contains almost no air bubbles. The lack of air means that it absorbs almost all visible light, apart from the blue fraction which is then visible to the naked eye.
However, this blue ice can be seen only under certain circumstances. It can be seen in winter after long periods of rain when the surface layer of the glacier has been washed away. It can be seen in ice-caves like this one and on floating icebergs that have recently rolled over.
This cave in the glacier ice is the result of glacial mill, or Moulin where rain and melt water on the glacier surface are channeled into streams that enter the glacier at crevices. The waterfall melts a hole into the glacier while the ponded water drains towards lower elevations by forming long ice caves with an outlet at the terminus of the glacier. The fine grained sediments in the water along with wind blown sediments cause the frozen meltwater stream to appear in a muddy colour while the top of the cave exhibits the deep blue colour. Due to the fast movement of the glacier of about 1 m per day over uneven terrain, this ice cave cracked up at its end into a deep vertical crevice, called serac. This causes the indirect daylight to enter the ice cave from both ends resulting in homogeneous lighting of the ice tunnel.
The cave is accessible through a 22-foot entrance on the shoreline. At the end it tapers to a tight squeeze no more than four feet high. Ice caves are in general unstable things and can collapse at any time. They are safe to enter only in winter when the cold temperatures harden the ice. Even so one could hear constant cracking sounds inside the cave. It was not because it was going to collapse but because the cave was moving along with the glacier itself. Each time the glacier moved a millimeter loud sounds could be heard.