Asteroid Impact Infograph (IMAGE) University of the Witwatersrand Caption A model for the compositional evolution of the early Earth's crust due to fractional crystallization of impact melt sheets followed by detachment and sinking of their dense primitive portions towards the crust-mantle boundary. Credit Rais Latypov Usage Restrictions None License Licensed content Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.