WASHINGTON (AFP) A massive crack is growing wider in the Antarctic ice sheet and could break apart in the coming months, forming an iceberg the size of New York City, NASA scientists warned on Thursday. The crack in western Antarcticas Pine Island Glacier stretches for at least 18 miles (30 kilometers) and runs 165 feet (50 meters) deep. The rift is widening at a rate of 6.5 feet (two meters) per day, said NASA project scientist Michael Studinger. When the ice breaks apart, it will produce an iceberg more than 340 square miles (880 square kilometers), said Studinger, who is part of the US space agencys IceBridge project. But the process is not a result of global warming, he said. We expect that later this year or early next year there will be a pretty large iceberg forming as part of a natural cycle, he added. These are cyclical events that occur every few years. The last big calving event occurred in 2001, so in general people have been expecting something to happen like that very soon. For us it is very exciting to actually see this while it is happening.