Plate motions for the past 500 million years demonstrate the rise and fall of latest supercontinent Pangea. The new 'orthoversion' theory of the supercontinent cycle predicts a future supercontinent forms at the edge of the previous supercontinent (blue), 90 degrees away from the center of the previous supercontinent (yellow). Back-and-forth motions of all continents about a stable axis on the equator allow the center of a supercontinent to be quantitatively measured.