Q: I am currently studying plate tectonics and references are made to 'major' and 'minor' tectonic plates. Is there ay framework as to which is which? Nazca for example is neither as large nor small as many other plates. How would it be classified?
From Mr S Lolley (April 2010)
Reply by Dr Ted Nield These divisions are inevitably somewhat arbitrary, but by convention we recognise seven main or “primary” tectonic plates: these are the African Plate: Antarctic Plate, Eurasian Plate, Indo-Australian Plate, North American Plate, Pacific Plate, and South American Plate.
You mention the Nazca plate as not being particularly “minor”, and indeed there is an intermediate grouping, normally said to comprise the Arabian Plate, Caribbean Plate, Cocos Plate, Juan de Fuca Plate, Nazca Plate, Philippine Sea Plate, and the Scotia Plate. This is easy to remember because they also number seven!
All the rest are “tertiary” plates, and there is a very long list of them.
You can find a lot more about this on Wikipedia, which has a very good entry on this subject:
http://en.wikipedia.org/wiki/List_of_tectonic_plates