Early Tectonics

摘要

Plate tectonics, crucial for creating the oceans and atmosphere essential for life, began around a billion years earlier than we thought. Michelle Hopkins and colleagues at the University of California, Los Angeles, have found evidence of tectonics in zircon deposits that formed about 4 billion years ago. Analysis showed that minerals trapped within the zircon crystals had formed at a lower temperature and higher pressure than expected for crust of that age (Nature, vol 456, p 493). This suggests that the crystals had been formed in a subduction zone, where one rocky tectonic plate plunges beneath another, showing that plate tectonics was up and running at this time. While chemical traces in zircons have hinted that tectonics began this early, this is the first direct evidence from actual minerals of the period, says co-author Craig Manning.