The onset timing of plate tectonics  

  

Plate tectonics is widely accepted as a fundamental theory in Earth science and is hailed as an important scientific discovery of the 20th century. However, the major challenge of the theory since its foundation for half a century now is the debate over when Earth first developed plate tectonics—4 billion years ago vs. 1 billion years later—an uncertainty which spans nearly three-quarters of Earth history. Dr. Bo Wan innovatively proposed that the global subduction network is an important signpost to identify the onset of modern plate tectonics. He creatively carried out high-resolution and comprehensive geological and geophysical observations of the northern margin of the North China Craton. He first recognized key information supporting significant horizontal movement and subduction of an oceanic plate at a convergent tectonic boundary nearly 2 billion years ago, and reconstructed the position of North China in the Earth’s first supercontinent based on its iconic subduction record. He further revealed the geophysical interface preserved by the ancient continental convergence. These features are identical to the surface and deep structure of the modern Himalayan orogenic belt, indicating that North China underwent a similar geological process at 2 billion years ago. Putting the key findings from China in a global context, Wan proposed that the earth gave birth to its global plate subduction network 2 billion years ago, leading to the formation of Earth's earliest supercontinent due to the pulling forces of subduction. Only after the onset of the global plate tectonic network did the earth start the cyclic assembly and dispersal of supercontinents. Such active plate margin led to intensive mass and energy exchange between Earth’s surface and interior, which was an important driving force for maintaining planetary habitability. The onset of plate tectonics signifies the contrasting evolutionary paths between Earth and other planets.