"The ice has time to spread out and become perfectly flat", Poinar adds, so when an iceberg breaks off from a large ice shelf along an existing fissure, it looks like a large, flat rectangle. Scientists have documented this sort of thing before, but this latest 'berg, which recently split from Antarctica's Larsen C ice shelf, happens to be a rather extraordinary example.
Such objects are not unknown, however, and even have a name - tabular icebergs.
Covering an estimated 5,800 sq km, the Larsen C ice shelf extends along the east coast of the Antarctic Peninsula from Cape Longing to Smith Peninsula. "You can just get these fracture lines that can form these interesting geometric structures", he says, and points out a different, triangle-shaped iceberg spotted by NASA scientists recently.
The size was hard to guess, Ms Brunt said, but suggested it was likely more than a mile long.More news: Anthony Kiedis Ejected From LeBron James’ First Home Lakers Game
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"What makes this one a bit unusual is that it looks nearly like a square", she told the LiveScience website.
"My guess is that A68 will continue rotating as it is now around that western point, until what is currently the northern edge collides with the Larsen C ice front".
And as with all icebergs only 10% of it is visible; the rest if buried below the surface of the water.
That was not the only shape that scientists spotted last Wednesday.