The Avalon TerraneIt’s rather remarkable that right now, a person in Poland is standing on a s
The Avalon TerraneIt’s rather remarkable that right now, a person in Poland is standing on a slice of the same crust as the inhabitants of London and as visitors to Boston’s Fenway Park. This map shows the re-assembled Avalon terrane, with spreading of the Atlantic Ocean removed, and marks modern day political boundaries. The Avalon terrane or Avalonia formed originally as an island arc off the coast of Gondwana, connected to or at least close to what is today West Africa. It is made of a mixture of large igneous bodies and sedimentary rocks, as would be found today at many oceanic island arcs above subduction zones. That slice of crust was rifted away from Gondwana and moved across the Iapetus Ocean, eventually colliding with one of the other ancient blocks of crust wandering the world, Baltica.The collision with Baltica set off the first part of the Caledonian Orogeny, a period of mountain building in the Silurian and Devonian recognized by folded rocks throughout Scotland, Ireland, Scandinavia, and Greenland. That orogeny continued because shortly thereafter the combined Avalon and Baltica continent began impinging on the Laurentian craton that today makes up the heart of North America. This collision assembled Laurentia, Baltica, and Avalonia into a single supercontinent and triggered the Acadian Orogeny in North America.A few other crustal blocks, such as Iberia, later collided with this assembled continent to finish assembling what we know of as Europe today. A few hundred million years later, this crustal block collided with Gondwana to assemble the supercontinent Pangaea.When Pangaea rifted apart, Avalonia was sliced in two. Pieces of Avalonia now make up the heart of Northern Europe’s crust and parts of New England; a half-billion year old connection between the two continents.-JBBImage credit: https://commons.wikimedia.org/wiki/File:AVALONIA.jpgReferences:http://specialpapers.gsapubs.org/content/423/375.abstracthttp://bit.ly/29eBG7uhttp://www.globalchange.umich.edu/ben/publications/gsab01.pdfhttp://bit.ly/29jCSrphttp://sites.williams.edu/geos101/ -- source link
#geology#continent#avalonia#plate tectonics#poland#england#wales#new england#orogeny#acadian#science#pangaea#continental drift