Glaciations of the San Juan Mountains: A review of work since Atwood and Mather
— B. Johnson, M. Gillam, and J. Beeton

Atwood and Mather’s 1932 map of glaciers restored to their Last Glacial Maximum (LGM) dimensions in the San Juan Mountains is the starting point for any geomorphologist working in the region. Here, we examine more recent work completed in the Animas valley and eastern and central San Juan Mountains to update the work of Atwood and Mather. Specifically, we look at attempts to constrain the timing of glaciation using methods developed since the publication of the original map. We also present modern field descriptions of a number of sites and discuss the morphology of glacial landforms. Much of the work done in the San Juan Mountains has not been published and here we attempt to present as much of that data as possible. This examination of previous work highlights the detailed pre-LGM stratigraphy of the Animas Valley compared with moraines in the eastern and central San Juan Mountains which tend to be LGM in age.