Just a trick of the image. Seen from space, this particular iceberg has a rich diversity of sharp-edged friends — and although it initially seemed perfectly rectangular, it's not.
The black arrow points to the iceberg in question.
"and although it initially seemed perfectly rectangular, it's not. The black arrow points to the iceberg in question."
That's just a trick the aliens use to disguise their handiwork from other aliens out there who may be watching.