The area around John Day contains some of the most important paleontological resources known. From about the time the dinosaurs disappeared right up until the Pleistocene, the region was subjected to significant volcanism and other processes that preserved many fossils. Because the matrix in which the fossils are entombed is datable, the fossils themselves can be dated with excellent precision. This gives paleontologists the ability to study how species changed over time and also how the relationship between ecosystems and climate changed.