New study suggests that plate tectonics did not create the continents
A study published by researchers at the Queensland University of Technology have suggested that "gravitational overturn events" are responsible for creating stable continents.
The East Pilbara craton in Western Australia is a stable area of continental crust and is considered "a natural laboratory for Early Earth research". Rocks from the East Pilbara craton were analysed and dated to ~3.6 billion years ago, a time when the Earth's mantle was at its hottest.
Their analysis indicates that these rocks were not formed through tectonic events but through gravitational overturn events, where denser materials mixed down into the hotter mantle below and lighter materials rose to the surface. These events caused the chemical and thermal mixing that led to the emergence of stable continents.
The researchers suggest that the East Pilbara craton was affected by three successive gravitational overturn events, in 100 million year cycles, before plate tectonic processes took over 3.2 billion years ago. Similar cycles could also explain the creation of stable cratons in India and Africa.
“Our research has provided direct evidence of the processes that were occurring [during early Earth] and will provide valuable input for modelling of how our planet came to be, the architecture of its crust and where mineralisation occurs,” said Dr David Murphy, one of the researchers.
Image created by Hesperian