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Sunday, April 8, 2012

Geological Time

Geology is a big subject. Can geological time be bigger? I've thought to learn a bit about both. You may find my blundering less upsetting if your ignorance is o f a magnitude close to mine. Familiarity with related vocabulary may help. I'll start with the names for some periods of geological time:
A super eon is composed of eons.
Eons are divided into eras.
Eras are divided into periods.
Periods are divide into epochs.
Epochs are divided into ages.
Ages are divided into chron.

Well, that was a big help.

Examples might help:
An example of a super-eon would be the duration of the Precambrian: 4000 million years(?!) I guess that means that the Precambrian time is a super-eon. What's a Precambria? What's a Cambria? Have I started backwards?

An example of an eon would be the Archean. Strangish vocabulary. This is going to take some sorting out.

An example of an era would be the Mesozoic. I've heard of the Mesozoic. Meso- means something like middle and -zoic refers to life forms. Maybe eras are marked by life forms. Maybe listing eras chronologically would be clarifying.

An example of a Period is the Camoan. It seems the Camoan Periods began 550 million years ago and lasted to 490 million years ago. Geological time! What is a Camoan. Who knew that there was more than one of the.

23 million years ago to 6 million years ago seems to be the measure of the Miocene Period. It seems that all Periods are not equal. I wonder how it is decided to end one Period and to begin another.

What I once heard called the Tertiary Period ended one or two million years ago and began with the end of Non-avian dinosaurs. The Tertiary may be obsolete. Is a Period marked by life forms. What is the difference between a dragon and an avian dinosaur? I think some dragons are more worm-like than birdlike.

This is pretty confusing. I need a better plan, better questions, or something. I bet a historical look would be helpful.

I'll make a few more notes anyway.

The Paleogene Period is made up of of the Paleocene, Eocene, and Oligocene epochs.

The Neogene Period has the Miocene and Pliocene epochs in it.

The Pleistocene epoch began about 2,588,000 yeqrs ago and con tinued to about 11,700 years ago. That's getting pretty close to home. The Pleistocene epoch follows the Pliocene and is followed by the Holocene epoch. It is my guess that we are in the Holocene. The Pleistocene is the first epoch of the Quaternary Period; whatever that means.
Eleven major glacial events occured in the Pleistocene epoch. An Epoch is made up of ages, so might a glacial event be an ice Age? How are glacial events detected?

What are Milankovich cycles? Russian?

What are oxygen isotope ratio cycles?  Oh, oh! This sounds like chemistry, physics, and math.

How are the beginnings and ends of epochs marked

Okay, that's it for now. Let's not quit completely yet.

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