Calgary's Glenmore Reservoir ice circle: mysterious or logical explanation?

People are asking a lot of questions about a mysterious "ice circle" that appeared on the frozen surface of Calgary's Glenmore Reservoir.

A unique design appeared carved out on the GlenmoreReservoir two concentric circles with arrows pointing towards a centrebullseye.

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Curious onlookers guess everything from an icy crop circleto a children's game carved into the snow.

But the Calgary Fire Department has a very logical reason for the icy design.

"It's actually for dive team training," said fire department spokesperson Carol Henke.

The fire department is training several new dive team recruits and beneath the surface are underwater safety ropes for divers to hang onto.

The shovelling pattern is a back-up safety precaution.

"Removing several inches of snow allows more light to go through the ice so, should they come off the rope, they could look up at the ice and see the outline of the circle and the arrows pointing to the hole in the ice," she said.