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Monday, October 17, 2005

Now, the Holocene, the Cenozoic

The Cenozoic is the present and most recent of the four geological eras. It was preceded by the Mesozoic era which encompassed the the Triassic, the Jurassic and the Cretaceous periods. The dinosaurs died at the end of the Cretaceous period 65.5 million years ago. The Cenozoic is the age of mammals. In the last 65.5 million years we hairy milk producing beasties have evolved into a diverse collection of land, sea and flying mammals. However our history began long before then as we mammals coexisted with the dinosaurs.The Cenozoic could also be called the age of birds, insects and flowering plants as they have also evolved to the same degree during this time.

The Cenozoic is also divided into subsections. It consists of the Tertiary and the Quaternary. The Tertiary is divided into the Neogene (which covers the Pliocene and the Miocene) and the Paleogene (which covers the Oligocene, Eocene and Paleocene). These terms are as familiar to scientists as phrases like ‘early modern’ or ‘divine right of kings’ are to historians. In the last week I have struggled to learn about natural history because I lacked an understanding of this basic vocabulary. I hope I haven’t made any mistakes in this article because all the new words are a bit confusing.

We live in the Quaternary, which stretches back to about 1.6-1.8 million years ago. Recent changes in international classification have subsumed the Quaternary into the Neogene. Assuming for now that we can still use the term Quaternary, it is itself divided into the Pleistocene and Holocene epochs. The last 10, 000 radiocarbon years (each year equal to 1.3 normal years) have been the Holocene. If I’ve understood it correctly a glacial period divided the Holocene and Pleistocene. A glacial period is not the same thing as an ice age. I think an ice age covers warm and cold periods known as glacial and interglacial. The Holocene is an interglacial period. I’m a little bit confused but I assume the ice age is over and we’re not just in a lull. Are we?

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