 Much of central England formed a stable block of crust which has remained largely undeformed ever since.500 million years ago, in the Ordovician period, southern Britain, the east coast of North America and south-east Newfoundland broke away from Gondwanaland to form the continent of Avalonia.The Skiddaw slates of the Lake District consist of metamorphosed marine sediments laid down on the northern margin of Avalonia.