The formation of the ozone layer
The formation of the ozone layer
The 4 eras are Cenozoic era, the mesozoic era, the paleozoic era, and the precambrian era.
During the Cenozoic era, which began around 66 million years ago, dinosaurs went extinct at the end of the previous Mesozoic era. Therefore, the existence of dinosaurs is something that did not occur during the Cenozoic era.
No, the most well-known Ice Age was in the Cenozoic Era, during the Pleistocene epoch.
We are currently in the 21st century. We entered the 21st century in 2001.