AN unusual natural phenomenon almost never seen in the UK has been observed in the Tyne Valley.

Hexham resident Alison Lee was out walking near Dilston on Thursday, January 31, when she saw a large, almost perfectly circular slab of ice floating down Devil's Water.

Known as ice circles or ice disks, the strange phenomenon occurs in slow moving water in cold climates.

Aidan Pollard, Fisheries Manager at Tyne Rivers Trust says: "It’s a bit like a snowball forming. Ice particles in the river are caught in an eddy - a circular current - which has just enough energy to keep turning the collecting particles in a circular motion so that they form a circular mass. "The mass keeps growing, gathering more ice to reach the largest circle the current can support."

The Met Office refers to the phenomenon as "ice pancakes."

A spokeswoman for the weather service said: "Ice pancakes are relatively rare phenomenon that tend to occur in very cold oceans and lakes. "They are most frequently seen in the Baltic Sea and around Antarctica but also form relatively frequently on the Great Lakes of the United States and Canada."

Ice disks are very rare in the UK, however.

In 2009, an ice circle spotted in Devon made national headlines, and was thought to be the first time the phenomenon had been observed in the UK.