 But you've also got these diatom layers where diatoms are a kind of algae. And the diatoms tend to be whitish in color. So you've got these white and gray banding patterns that show up. Well, the typical assumption with these couplets is that you have one per year. If you assume that it's one per year, that's what you call a varve. And varves are a favorite argument for many old earthers to try to argue with.