The last rays of the day are reflected in the tip of a translucent iceberg with its hexagonal ice crystals and fern-like branches on Mendenhall Lake yesterday evening. The cold weather has transformed Mendenhall Lake into one giant skating rink. Icebergs are now more accessible than ever before, though the threat of instability remains a constant. It’s easy to forget that this is a dynamic environment. Because of the constant erosion of the base of icebergs by lake water, any iceberg could flip on its side or turn upside down at any time.