関連ワード:  why is plate tectonics a theory    why is plate tectonics a theory and not a law    why is plate tectonics a unifying theory in geology    why is plate tectonics still a theory    why is plate tectonics considered a theory    why is plate tectonics a unifying theory    why is plate tectonics a scientific theory    why is plate tectonic theory important    why is plate tectonics called a unifying theory    is plate tectonics a theory or fact