Researchers noticed a giant crack in the middle of the Brunt Ice Shelf in Antarctica.
How it'll happen: Two cracks in the shelf will lead to massive break-off. The Halloween crack, which first appeared in October 2016, will move eastward.
The second crack, which breaks off northward, has been fine for 35 years according to CNN. But that second crack started accelerating at about 2.5 miles per year. Once the cracks meet, the iceberg will be born.
When the crack widens enough, it will create an iceberg measuring about 660 square miles, according to USA Today. New York City measures 302 square miles.
"We don’t have a clear picture of what drives the shelf’s periods of advance and retreat through calving," said Chris Shuman, a glaciologist with NASA and the University of Maryland Baltimore County, in a statement. "The likely future loss of the ice on the other side of the Halloween Crack suggests that more instability is possible."
NASA did not confirm when it will happen. The agency said it is “poised” to happen, CNN reports.
The Brunt Ice Shelf currently leans out of the Weddell Sea just south of South America, according to CNN.