I just read this article, http://www.cnn.com/2001/TECH/science/05/10/mass.extinction/index.html
I’m wondering, if this WAS caused by an asteroid, and occured before the breakup of the super continent, would this have had an effect on plate tectonics? If movement of plate tectonics has always been, why would the earth have only a single continent?
My guess as to the single continent is that at some point they all got smooshed (if that’s a word) together. Given constant movement through plate tectonics, odds are at some point all the plates would run into each other.
regarding the linked article, don’t they have the period boundaries wrong? I’m not aware of any great extinction between the Triassic and Jurassic periods. There was a big one at the end of the Cretaceous (end of age of dinosaurs) and a much more massive one earlier at the end of the Permian (beginning of age of dinosaurs). Of course IANAP…
The supercontinent of Pangaea formed gradually through collisions between various land masses throughout the Paleozoic, and was fully formed by the Permian. It was intact through much of the Triassic, but began to break up in the Jurassic. An asteroid impact would be very unlikely to have much effect on plate tectonics, which is presumed to be driven through internal convection. However, it has been postulated that one could trigger massive flows of basalt such as the Deccan and Siberian Traps.
The Triassic-Jurassic mass extinction is one of five or six such events usually recognized. The others are:
Late Cambrian
Late Ordovician
Late Devonian
End Permian (Permian-Triassic)
End Cretaceous (K/T)
I realise this is difficult to explain without drawings and maps, but have those points of convection and merging changed over history? Or, have they always occured at the points that we know today to be active? If Pangea was located in say, the eastern hemisphere, why wouldn’t additional continents be forming in the western hemisphere?
They have changed greatly over geological time. As for drawings and maps, check out this site for zones of spreading and subduction at various times in Earth history.
New continental masses do not form, or at least have not for billions of years. The cores of each present continent, the “cratons” (e.g the Canadian Shield of North America, the Guiana Sheild of South America) are extremely ancient. These continental masses have grown over time through accretion of volcanic materials at their edges when oceanic plates are subducted beneath them, or by the collisions with islands formed at oceanic ridges or at hot spots (exotic terranes). Much of western North America has been “plastered” on to the core of the continent by such processes.
There were supercontinents long before Pangaea formed, and the continents will coalesce again about 250 million years from now.
thanks for the information and link to the site.
My impression was that geologists thought plate tectonics had been around since the beginning of the Earth, but it appears I was wrong: check out this article:
http://www.cnn.com/2001/TECH/science/05/11/tectonics.reut/index.html