|
 |
An Interactive Handbook in Natural Resource Management
Geologic Time
The faunal resource manager is steeped in the past for it is the source of life, the time in which a million million selective forces worked on animals, and the deep spring from which the wonders of genetics and heredity may be drunk. Some managers believe that geology needs to be mastered, not to learn about rocks but about time. This unit is a refresher outline on the major time elements of geologic history and their faunal associates. Discoveries are made almost daily so this unit may be quickly dated. It is one that should be edited by the reader.
There were two eons.
The Earth may be about 7 to 9 billion years old. That estimate is the beginning of the Cryptozoic eon.
The Earth accretion may have been completed about 4.6 to 4.7 billion years ago.
The oldest dated rocks are 3.4 plus or minus 0.1 billion years old.
There are four eras.
It is usually helpful to think of the periods in the way that rock strata might be laid down, i.e., from the bottom up; oldest first.
The area manager realistically needs to deal only with the upper three...
The Paleozoic contains six Periods...
|
6 |
The Mesozoic era contains three periods...
The Cenozoic Era of the Phanerozoic Eon contains no Periods. Instead, there is more detail and evidence within the more recent strata of Earth so more refined categories are possible.
The word Epoch is used.
Within the Cenozoic are...
The following are brief notes on each unit of geologic time...
Phanerozoic Eon - Paleozoic Era
Period... Cambrian - Fossils first abundant. Period began 570 million years ago. Duration: 70 million years.
Ordovician - First invertebrates were abundant. Began 500 million years ago. Duration: 70 million years.
Silurian - Amphibians evolved from lung fish. Began 430 million years ago. Duration: 35 million years.
Devonian - First forests appeared. Began 395 million years ago. Duration: 50 million years. years.
Carboniferous (Mississippian and Pennsylvanian [most recent]) - Reptiles and amphibians appear. Began 345 million years ago. Duration: 65 million years.
Permian - Continental uplift. Began 225 million years ago. Duration: 35 million years.
This unit has provided a brief look at the six Periods of the Phanerozoic Eon containing the Paleozoic Era.
Next come notes on the Mesozoic Era.
Phanerozoic Eon - Mesozoic Era
Triasic - Small dinosaurs and first mammals. Began 225 million years ago. Duration: 35 million years.
Jurassic - Dinosaurs dominant. Began 190 million years ago. Duration: 54 million years."
Cretaceous - Dinosaurs (60 to 70 million disappeared). Began 136 million years ago. Duration: 71 million years.
The above has been a review of the three periods of the Mesozoic Era of the Phanerozoic Eon -
Now for more recent events...
Phanerozoic Eon - Cenozoic Era
Eocene
Oligocene
Miocene - Mammals climax.
Pliocene - People emerge.
Pleistocene - The stone age and massive glaciation.
Recent
This completes the unit on geologic time. The purpose has been to allow recall of earlier class work, to thereby enhance scientific reading. It has also been to encourage continual exploration of means to help people understand the life processes of the faunal management areas. Only a cad can gaze at a fossil without wonderment and amazement. In the fossil record of extinction are surely messages for all faunal managers. and for society itself.
Please go to the Capper Contents for other teaching / learning units.
| Capper Contents |
Perhaps you will share ideas recent findings about some of the topic(s) above .
Home
Rural System
Glossary
Robert H. Giles, Jr.
July 4, 2006