I thank C. Badgley, C. Garzione, J. Quade, and R. Van der Voo for thorough reviews of different versions of the manuscript, and the editors for soliciting a paper in honor of Will Downs, a special person. Garzione, in particular, pointed out a number of implications of stable isotopes that I had overlooked, and Quade called attention to one potentially illogical inference. C. Petit guided me on literature concerning the Baikal Rift zone. R. Aalto offered an explanation for the decrease in sediment accumulation rates in the Bengal Fan. Support from the National Science Foundation under grant EAR- 0435795 motivated this research.