That change means recent events recorded in the rocks are much better known than the older happenings of our earth, and the events of the very early world are mostly unknown. There are no fossils in the oldest rocks because there were no living things. In this geologic column, it is younger on the top than on the bottom, just like the piles of paper on my desk, or a layered sequence of sedimentary rock. Four major divisions Roughly, we can divide the time column into units comprehensible to us by saying the Cenozoic was the past time from present day back to the disappearance of the dinosaurs. Volcanoes and erosion are also active forces that shape the land.
Volcanoes bring up new material for land, erosion wears it down.
That's part of the rock cycle. Here is a map showing the regions of Arkansas today. The timeline summary below tells you how our part of the world got like this. Wind blown dust and sand dunes, along with stream deposits covered portions of the land, but erosion was also active, and carried away surface material. The Ozark highlands of north Arkansas looked similar to the canyonlands of the western United States today.