Image: Risto Mattila

Oulu resident and amateur photographer Risto Mattila was in for a bit of a shock when he came across a host of odd-looking "eggs" on a beach during a Sunday stroll on Hailuoto island, northern Ostrobothnia.

Piled up on the Marjaniemi beach was a 30-metre-wide collection of objects that looked like large eggs. Mattila said he had never seen anything like it during 25 years living in the vicinity of the sea. Other people out and about on Sunday afternoon were also mystified by the egg-shaped ice and snow formations.

"My wife and I stood there marvelling at the remarkable natural phenomenon. Since I had a camera with me I decided to preserve this unusual sight for posterity," Mattila added.

A rare phenomenon

Jouni Vainio, an ice specialist from the Finnish Meteorological Institute (FMI), said that the ice eggs were not a supernatural phenomenon, although they were rare. He noted that the formations require just the right air and water conditions, which have to be near freezing.

The shallow sandy beach and just the right ebb and flow of the frigid water would be almost enough for the "eggs" to form, he explained. However there would also have to be another factor to allow the ball of snow and ice to form around it.

That could be a snowflake, a small stone on the beach or even a bit of flotsam in the sea. The water would then freeze around the object, while a suitable wind would ensure continued ice build-up with the back and forth movement of the water.

"Too much wind would prevent the ball from forming. On the other hand, if it’s calm, [the water] would just freeze on the beach in an even layer," Vainio continued.

Mattila’s encounter with the ice eggs was serendipitous, because they are usually only discernible for a short time. Regular shoreline conditions such as a high wind can easily cause them to accumulate into a large deposit of ice in which the individual eggs would no longer be visible.