Irish-Scottish rock formation may be rare record of ‘snowball Earth’ period

Researchers say exposed rock shows transition from warm, tropical environment to global freeze about 700m years ago

A rock formation that spans Ireland and Scotland may be a rare record of snowball Earth" - a crucial moment in planetary history when the globe was covered in ice.

The Port Askaig Formation, which is made up of layers of rock up to 1.1km (0.7 miles) thick, is likely to have been laid down between 662m and 720m years ago during the Sturtian glaciation, research suggests. This was the first of two global freezes thought to have triggered the development of complex life.