Slow start of plate tectonics despite a hot early Earth

Photo: © Christian S. Marien - Writing in PNAS, scientists from Cologne university present important new constraints showing that plate tectonics started relatively slow, although the early Earth's interior was much hotter than today. In an international collaboration earth scientists at the University of Cologne discovered that during Earth's early history mantle convection on, i.e. the internal mixing of our planet, was surprisingly slow and spatially restricted. This finding is unexpected because our planet was much hotter during the first hundreds of million years after its formation. Therefore, it has been assumed that mantle convection on Earth was much faster in its infancy. According to their study ,,Convective isolation of Hadean mantle reservoirs through Archean time", however, the earth did not experience full speed mantle convection until 3 billion years ago, when modern plate tectonics is believed to have fully operated. For their study, the geologists investigated up to 3.5 billion years old igneous rocks from NW Australia that cover 800 million years of Earths early history. The analysis of these rock successions revealed that the oldest samples exhibit small anomalies in the isotope abundances of the element tungsten (W) that progressively diminish with time.