An iceberg about twice the size of Washington, D.C., recently broke off one of the fastest-shrinking glaciers in Antarctica, worrying scientists that the glacier could be headed toward collapse.

Scientists at Copernicus, the European Union’s Earth observation program, have been monitoring the Pine Island Glacier since October, when large cracks appeared along its edge.

The Washington Post reports satellite data shows a chunk of ice more than 130 square miles broke off the glacier sometime between Saturday and Sunday.

According to NASA’s Earth Observatory, the calving event — the term for a large iceberg breaking off from an ice shelf — is not particularly threatening to global sea levels, as ice at the edge of the glacier was already floating, and will not directly contribute to sea level rise when it melts.

But the break is one of a series of calving events in the region that seem to be taking place more frequently in the region.

NASA reports that calving events used to occur at Pine Island Glacier every four to six years, but over the past decade, large chunks of the glacier have broken off about every two years. NASA reports that the region around the Pine Island Glacier, and the Thwaites Glacier, also known as the doomsday glacier, contain enough “highly vulnerable ice” to raise the ocean by four feet.

The two glaciers are considered the fastest-retreating glaciers on the continent. Researchers recently reported water under the Thwaites Glacier to be more than 2 degrees above normal freezing temperature. The amount of ice flowing out of Thwaites and nearby glaciers has nearly doubled for the past three decades.

Meanwhile, Antarctica marked its warmest temperature on record last week, at 65 degrees Fahrenheit.