Cosmic bombardment may have forged Earth's early continents
A new study argues that intense asteroid impacts during the Hadean heated and thinned Earth’s crust far more than internal heat sources, keeping the crust molten and preventing plate tectonics. As the impact flux waned around 3.9–3.5 billion years ago, internal heat then dominated, allowing the crust to thicken and enabling the rise of continental tectonics. This outer-heating scenario helps explain the scarcity of preserved Hadean crust and zircons, with lunar crater data helping calibrate the impact history and models predicting eventual crust recycling and the emergence of continents in the Archean.
