The Great Thaw
From ShireWiki
The Great Thaw was an event which occurred when the abnormal amount of cows began to release enormous amounts of methane in the form of flatulence into the ecosystem. This event caused disproportionate amounts of heat in Nordland, thawing the gigantic glaciers that Nordland is known for. This uncovered acres of ancient lands, including the discovery of the Ohl'Tar.