1. Department of Geosciences, Guyot Hall, Princeton University, Princeton, New Jersey, 08544, Magistère de Sciences de la Terre, École Normale Supérieure de Lyon, 46 Allée d’Italie, Lyon, France 69364, Department of Earth and Atmospheric Sciences, Harvard University, Cambridge, MA 02138, and U.S. Geological Survey, 431 National Center, Reston, VA 20192