Icebergs are not always uniformly white. Blue stripes are formed as iceberg layers melt and refreeze quickly, while green stripes are created by the freezing of algae-rich sea water. Other coloured stripes, such as black, brown and yellow, were created by sediment collected by the ice as it moved down a hillside towards the sea. As the iceberg melts, it often rotates to expose contrasting layers.
These icebergs may have taken hundreds or even thousands of years to form.