There are plenty of ways for an iceberg to make an entrance. This one, for instance, practically did a backflip.
A video from Iceland captures a massive piece of ice suddenly surging upward from beneath the surface, rolling onto its side and throwing an enormous section of blue-white ice into the air. As the berg completes its slow-motion somersault, water pours off its newly exposed face and a series of small tsunami-like waves radiates outward.
It looks bizarre, but there’s some serious physics behind it. See the video linked here and below.
One possible mechanism is submarine calving, when ice breaks away from the submerged portion of a glacier and buoyancy sends it rocketing toward the surface. The National Park Service describes these “basal bergs” as pieces of underwater glacier ice that “rise suddenly and unexpectedly,” sometimes emerging “explosively, without warning at the water surface.”
The U.S. Geological Survey has documented the same phenomenon at Alaska’s Columbia Glacier, describing an iceberg that “broke free from under the water and shot to the surface,” spinning as it emerged.
Once free, an iceberg may also roll because its shape is unstable. Researchers writing in the Annals of Glaciology explain that newly calved bergs often capsize as they seek a more stable orientation. That violent redistribution of mass releases gravitational energy and can produce “large-amplitude surface-gravity waves known as tsunamis.”
Related: Watch: Calving Glacier in Greenland Creates “Massive Wave” as Ice Crashes into Ocean
That’s exactly what makes the Iceland clip so mesmerizing — and slightly terrifying. The iceberg doesn’t simply float to the surface. It heaves upward, rotates, crashes back down and pushes a visible pulse of water across the lagoon.
Surfers have intentionally chased glacier-generated waves before. Garrett McNamara and Kealii Mamala famously surfed waves up to 25 feet generated by calving ice in Alaska, while more recently surfers including Blair Conklin have continued pursuing the bizarre phenomenon.
But this particular setup looks considerably less inviting.
There’s something about surfing next to a giant iceberg performing a surprise somersault that makes waiting for a normal swell seem perfectly reasonable.
Related: Collapsing Greenland Glacier Sends Giant Tsunami Wave Crashing into Tour Boat (Video)
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