The Cenozoic Era is one of the most exciting periods in Earth’s history, geologically, climatically, and biologically. It is also the most recent(and current) period of history. The Cenozoic Era is divided into two periods, the Paleogene and Neogene which are divided into epochs. The Cenozoic has seen the extinction of the non-avian dinosaurs and the rise of mankind. It is marked by the Cretaceous-Tertiary extinction event at the end of the Cretaceous period and the end of the Mesozoic Era. This era is the era of new life. Mammals may not have risen from the oceans at this time, but they did evolve into a diverse collection of terrestrial, marine, and avian forms.
The major geological happenings of the Cenozoic Era are that the continents moved into their current positions. After splitting with Gondwana during the early Cretaceous, Australis-New Guinea drifted north and collided with Southeast Asia. Antarctica moved into its current position over the South Pole and the Atlantic Ocean widened. Eventually, South America became attached to North America.
India collided with Asia between 55 and 45 million years ago; Arabia collided with Eurasia, closing the Tethy’s Ocean around 35 million years ago.
Climatically, the Cenozoic Era has been a long period of cooling. The creation of the Drake Passage caused South America to fully detach from Antarctica during the Oligocene, the climate cooled significantly because of the of the Antarctic Circumpolar Current which brought cool, deep Antarctic water to the surface. The cooling trend continued in the Miocene, with relatively short warmer periods. When South America became attached to North America(the Isthmus of Panama), the Arctic region cooled due to the strengthening of the Humboldt and Gulf Stream currents. This eventually led to the Pleistocene ice age.
Biologically, the Cenozoic Era is referred to as the Age of Mammals, even though birds outnumber mammals two-to-one. The Cenozoic is as much the age of savannahs, the age of co-dependent plants and insects, or the age of birds as it the age of mammals. Many species flourished have during this era. Grass has played a very important role in this epoch. It has shaped the evolution of the birds and mammals that feed on it. One group that diversified significantly in the Cenozoic are the snakes. During the Cenozoic, the snakes evolved into a wide variety of forms, especially colubrids, following the evolution of their current primary prey source, the rodents. In the early part of the Cenozoic, the world was dominated by gastornid birds, land based crocodiles, and a handful of primitive large mammal groups. As the forests began to recede and the climate began to cool, other mammals took over.
Here on Universe Today we offer a great article about the possibility that humans have changed the Earth enough that we are living in a new Era. Astronomy Cast offers a good episode about plate tectonics. These are some of the forces that helped to shape the Cenozoic Era.