Three of North America's Great Lakes freeze over

Three of North America's Great Lakes - Huron, Superior and Erie - have frozen over for the first time in nearly a decade after icy weather lasting more than a month.

Weeks of temperatures below minus 20 degrees have caused an ice blanket averaging as much as 60cm on the lakes, creating problems for shipping companies and ferries.

The three lakes are part of the five Great Lakes, including Lake Michigan and Lake Ontario, which constitute the largest fresh-water system in the world and represent 18 per cent of global fresh-water supply and 95 per cent of the US supply.