Caledonian folding

Back in the early Cambrian some 500 million years ago, the continental dance had an active phase that resulted in the assembling of many of the plate fragments that form the bedrock beneath the European continent. Chunks of rock that were joined then that have stayed together through the vagaries of supercontinental gathering (the formation of Pangaea, completed some 300 million years back) and dispersal. There were two main landmasses in those days, known as Gondwana and Laurentia (for a piece on the formation of Gondwana see http://on.fb.me/1D548m8).

Initially separated by a vast ocean, the tectonic process of subduction (whereby a dense and cool oceanic plate a long way from the hot spreading ridge of its birth sinks under another plate (marine or continental) down into the mantle) gradually brought them together and into collision. More vast mountains were born, whose roots strew a line from Scotland and Scandinavia, rocks were folded, heated, squeezed and melted into new shapes and minerals. This event is known as the Caledonian orogeny (a technical term meaning mountain building plate collision event) after the ancient Roman name for Scotland.

Several micro plates peeled off Gondwana, including Avalonia (the root of England and Wales and parts of Eastern North America), Baltica, parts of modern France and Spain, and got smeared and ground onto the edge of Laurentia. The process lasted around 150 million years as the Iapetus ocean disappeared. Volcanoes born during this time are still icons of modern geology, such as Scafell in Cumbria (see http://on.fb.me/1DSkORb) and the granites of Scotland and Mona. This photo was taken in a Scandinavian fjord, and shows some stunning folding, a distant memory of the first construction of something recognisable as Europa, though by now she is a grand old dame rather than a callow and tempestuous youth. Source: EarthStory

This entry was posted in Geology. Bookmark the permalink.

Leave a Comment (email & website optional)