~Icetunnel..

This up to 1000 years old snow has metamorphosed
into highly pressurized glacier ice that contains
almost no air bubbles.
Thus it absorbs the visible light despite the
scattered shortest blue fraction, giving it its distinct
deep blue waved appearance.
This cavity in the glacier ice formed as
a result of a glacial mill, or moulin.

Rain and meltwater on the glacier surface is
channelled 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 cerrac.
This causes the indirect daylight to enter the ice cave
from both ends resulting in homogeneous
lighting of the ice tunnel.
Source