The longest of these are periods, such as the Tertiary period, which spans from around 2.5 million years ago to 66 million years ago.
In the beginning of the Tertiary period, 70 million years ago, Arizona was flat and the river flowed in its present course, roughly east to west.
The ants' story has come alive in Poland where a pendant featuring the Tertiary Period work scene is one of the main attractions of Amberif, the annual amber trade fair.
The thin layer, which has been detected worldwide, is also considered the marker for the end of the Cretaceous and beginning of the Tertiary period, known as the K-T boundary.
Underwater volcanoes spread lava over a vast area, and when the ocean floor was pushed up during the Tertiary period, stratified landmasses were formed.
The tertiary period, which ran for a few million decades beginning in 65 million B.C., saw the rise of mammals, some of whom have received the benefits of tertiary education, otherwise known as college.
But the layer of rock just above it, which signaled the beginning of the later Tertiary period, lacked most of those Cretaceous species and contained only a few, much smaller species of forams.
The Cretaceous began 145.0 million years ago and ended 66 million years ago; it followed the Jurassic Period and was succeeded by the Paleogene Period (the first of the two periods into which the Tertiary Period was divided).
The term originally was applied to a formation of the Tertiary Period (later subdivided into the Paleogene and Neogene; 65.5 to 2.6 million years ago) occurring in the northern Alpine region but now denotes similar deposits of other ages and other places.
