Thursday, 29 March 2007

New discovery in Greenland changes our view of early plate tectonics

An exciting discovery was reported in Science this week as evidence of plate tectonics occurring 3.8 billion years ago turned up in Greenland. Plate tectonics is the large-scale movement of the Earth's crust. New ocean floor is made by the spreading apart of these plates at ocean ridges. It was previosly thought that during Earth's early years it was too hot for this process to have occurred in the same way as it does today, and some other methods of heat loss have been suggested instead. However, the recent discovery of ophiolite sequences (ocean crust that is exposed on land) in Greenland has confirmed that the same ocean spreading senario thought to happen today also occured 2 billion years earlier than previously thought.

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Malacoda said...

Hi Janine, am I right in thinking that the next oldest oceanic crust we have is Jurassic in age?

Janine Kavanagh said...

Hi Malacoda, yes i think you are right that the oldest crust is about 180 Ma, which makes it Jurassic. There are some nice maps of crustal age that you can see on google if you like.

By studying these conveniently uplifted and displaced ophiolote sequences (which have been saved from subduction) we've been able to "record" plate tectonics and the creation of the seafloor over a few billion years and apparently for most of Earth's history. Exciting stuff!

Cheers, good question :)