In just 30 minutes at the end of June, four-and-a-half miles of icebergs fractured off of Greenland’s Helheim glacier in an icy churn. Researchers managed to catch it on camera, and they’ve released a sped-up video that condenses the violence of the ice-shattering event into a little over 90 seconds.

The Helheim glacier dips into the ocean in eastern Greenland, and the first ice chunk to break off was wide and shallow, “like a pancake,” says David Holland, an NYU professor who led the expedition to Greenland. Then came the pinnacle icebergs — tall spikes of ice that toppled and turned. “Every conceivable type of iceberg was produced,” Holland says. All told, a section of the glacier as big as lower and midtown Manhattan combined broke apart and floated into the ocean, according to a news release, making global sea levels rise, just a little.

We can see the results of rising sea levels in the more frequent floods hitting our coasts at high tide. But it’s easy to forget the key ingredients feeding those floods. They include warming water, which expands and takes up more space, and land-based glaciers that dribble meltwater and drop chunks of ice into the ocean. Break an iceberg off a glacier, and it’s like plopping an ice cube into a cup of water, Holland says: the water line rises.

That makes sense — in the abstract. But it’s one thing to read about satellite images and aerial surveys that show the glacier shrinking. It’s quite another to see the glacier breaking apart up close. Watching the icebergs churn and float away from the glacier, it’s easy to see that there’s no putting the glacier back together again — at least, not anytime soon. It’s something Holland has been thinking about, too. “This process is very violent, very dramatic, and very one-way,” he says. “It raises sea level, and it does it very abruptly.”

Understanding when, why, and to what extent glaciers calve will be key to modeling how sea levels will rise as our planet continues to heat up. Looking down at the glaciers in Greenland and Antarctica from space, there’s certainly more of those fracturing events going on, Holland says. The hard part is predicting how much, and how often, glaciers might break in the future.

That’s why catching the glacier calving on camera was such a lucky break for the researchers, and it was thanks to the foresight of Denise Holland, who coordinates logistics for research programs at NYU’s New York and Abu Dhabi campuses. She, David Holland, and their colleagues were in Greenland to check on the equipment they use to monitor the glacier, and she set up the camera just in case. The team was getting ready to go to sleep when she heard the glacier’s normal cracks and rumbles change. “It’s hard to describe. It’s like a jet engine, lots and lots of big booms, and it ricochets all over the calving,” she says. “I turned on my camera, and I was lucky to catch what we saw.”