A map of Pangea overlaid with current country’s borders

[muriel_volestrangler]

12. Between about 500 and 400 million years ago, England, Wales, the New England and Nova Scotia coast

the south of Ireland and a bit of present-day mainland Europe (eg the Low Countries) broke away from Gondwana (ie the supercontinent which includes what is now Africa), to form Avalonia; this then collided with Baltica, to form most of present-day nothern Europe, and that combined mass then collided with Laurentia, which forms most of present-day North America. That collision formed the mountains in the British Isles - the Scottish side having been part of Laurentia.

http://en.wikipedia.org/wiki/Geology_of_Great_Britain

The combined supercontinent of North America and Eurasia, Laurasia, stayed together until the Atlantic starting forming - apparently it took from about 200 million years ago until 55 million years ago (roughly the era of the dinosaurs) to completely separate, and Scotland got left on the eastern side, while the New England coast, Nova Scotia, and most of Newfoundland were on the west, despite coming from Avalonia.