• Ultrahigh pressure (UHP) eclogite is absent from the rock record before c. 0.6 Ga. Continental crust (CC) has experienced secular change, becoming more felsic with time. Mafic Archean CC becomes too dense to exhume UHP conditions are reached. More mafic would have been submerged by a global ocean 1.3 km deep. Implications for hypotheses requiring subaerial land emergence of life. The absence ...