footprints in mud

At http://news.nationalgeographic.com/2016/10/ancient-human-footprints-afri… … we learn of the discovery of footprints near the volcanic mountain the Maasai call the Mountain of God. They are preserved in mud dating between 19,000 and 5,000 years ago (which is a large margin of error). There are some 400 footprints in an area the size of a tennis court, situated on the shore of a lake in Tanzania. The current view is that the mud dried out as quickly as a couple of hours.