In this photograph by Aoraki Mount Cook Alpine Village, we see the dark blue bottom of an iceberg in the terminal lake of New Zealand’s largest glacier, the Tasman Glacier.

According to dr_glaciology, the ice is so blue because it was near the bed of the glacier and thus under a lot of pressure from the overlying ice. The pressure means the ice lacks pockets of air, giving it the dark blue hue.

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In this rare sighting we see a black iceberg. According to the Canadian Encyclopedia:

Most icebergs are white except along freshly calved ice cliffs, which tend to appear blue. Others may appear green, brown or black, or combinations of these colours. These icebergs have usually rolled over, exposing basal ice, or have emerged from below water level. The various colorations are caused by differences in density, air-bubble content and impurities. For example, black ice is of high density and bubble free; dark layers indicate the presence of rock materials derived from the base of the parent glacier. Occasionally, rocks may be found on the original upper surface of the iceberg. As the iceberg melts, these materials precipitate into marine or lake sediments. [Source]

‘Calving’ occurs when a piece of ice becomes detached from its parent glacier, forming an ‘iceberg’. The photo was posted to Reddit by user Rundboll, although I was unable to determine who took the photograph. A reverse image search on Google and TinEye did not produce any concrete results.

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