A university campus-size iceberg spotted on the Antarctic peninsula margins is upending public expectations of classic Titanic-esque icebergs with sharp spires jutting from the ocean surface.

An aerial photo shared by NASA captured a rectangular slab of ice sliced so smoothly that it appears unnatural. Experts say they believe the iceberg fractured in May from Larsen C, a large ice shelf fed by several glaciers on the east side of the peninsula. They're still unsure whether it will cause the rest of the shelf to destabilise.

"Ice shelves release large icebergs from time to time. They do this naturally," said Christopher Shuman, a research scientist at the University of Maryland Baltimore County's Joint Centre for Earth Systems Technology at NASA. It means that the ice shelf is changing, which is not surprising given the changes scientists have seen nearby, he said.