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Earth Transcription

Earth is four and half billion years old and may have looked more like the planet Mercury. For a billion years meteorites and comets impacted the planet. The hot core created convection currents in the mantle. The crust cooled and separated into lighter continents at the surface, while denser ocean crust sank into the mantle and re-melted. Lighter continents almost float on the denser ocean crust and mantle. Continents appear to ‘drift’ a few centimeters a year from place to place. Old crust blocks exist as the cores of modern continents. The oldest known rocks are in the Canadian Shield, dated to four billion years. Ocean crust is 200 million years old or less. It is created at seafloor volcanic chains and destroyed at subduction zones in deep ocean trenches.

850 million years ago continents were arranged as a supercontinent called Rodinia. As continents move, they are sometimes pushed together to form supercontinents, while other times they are broken and scattered across the globe. Some scientists believe Earth was almost entirely covered by ice about 700 million years ago. Starting 600 million years ago, fragments were torn away from ancient ‘South America’ and ‘Africa’. The Iapetus Ocean, separating them from ‘North America’, began to close. 490 million years ago the terranes called Ganderia and Avalonia began moving toward ancient North America. 455 million years ago Ganderia and Avalonia approached ancient North America. The Iapetus Ocean was subducted beneath North America. Volcanic island chains were created. 435 million years ago pieces of ancient ‘South America’ and ‘Africa’ collided with the old core of ‘North America’, this was the start of New Brunswick. By about 360 million years ago the supercontinent Pangea was formed. New Brunswick was near the equator. 300 million year old rocks and fossils in New Brunswick are almost identical to their counterparts in Great Britain and Europe. They were all part of the same continent of Pangea when they were formed. About 250 million years ago a new ocean was created. The Atlantic Ocean split Pangea into pieces. North and South America were on one side of the new ocean – Europe and Africa were on the other side. For the past 200 million years the Atlantic Ocean has slowly widened.  At 50 million years ago the globe looks very similar to the modern world. Although the distance between New Brunswick and Europe has increased, we still have very similar rocks from before the breakup.