Earlier papers in this series addressed the climatology and historic observations of the Medieval Warm Period and Little Ice Age and how the data obtained from the Little Ice Age should constrain our study of climate change and our speculations regarding previous glaciations. In this final paper of the series, geologic observations resulting from the Little Ice Age are presented. As climatologic observations from recent centuries should constrain paleoclimatology, so also should geologic observations from Little Ice Age deposits constrain our interpretation of apparently glacial deposits elsewhere.