Why aren't continents defined by plate tectonics?

California is on the edge of the North American plate and on the edge of the Pacific plate (the western Edge of Southern California from about San Francisco south). It's geological problems are caused by the plates moving past the North American plate.

 

Zealandia: Is there an eighth continent under New Zealand?


17 February 2017

From the section Asia
You think you know your seven continents? Think again, as there's a new contender hoping to join that club.

Say hello to Zealandia, a huge landmass almost entirely submerged in the southwest Pacific.

It's not a complete stranger, you might have heard of its highest mountains, the only bits showing above water: New Zealand.

Scientists say it qualifies as a continent and have now made a renewed push for it to be recognised as such.

In a paper published in the Geological Society of America's Journal, researchers explain that Zealandia measures five million sq km (1.9m sq miles) which is about two thirds of neighbouring Australia.


continued

http://www.bbc.com/news/world-asia-39000936

 

Exactly...so which continent would it rest on?

This is why the plates cannot be used to define a continent.

 

Well, part of California rests on the NA plate. Part of California rests on the Pacific plate. I agree, plates can't be used to define a continent. IMHO, it's a combination of culture and physical features. Otherwise, Europe and Asia would be considered the same continent. Most of Europe and Asia are on the Eurasian plate (with the eastern, and southern parts of it being on other plates).