Geological time scale
| Era | Period | Plant and Animal Development |
|---|---|---|
| Cenozoic | Quaternary | Humans develop “Age of mammals” Extinction of dinosaurs and many other species. |
| Tertiary | ||
| Mesozoic | Cretaceous (144) | First flowering plants First birds Dinosaurs dominant. |
| Jurassic (206) |
What are the major eons eras and periods in geologic time?
Eons are made up of eras, divisions that span time periods of tens to hundreds of millions of years. The three major eras are the Paleozoic, the Mesozoic, and the Cenozoic. The Cenozoic era is the one we are in today. It began 65 million years ago, right about the time that the dinosaurs went extinct.
What are eons eras periods and epochs?
eon = The largest unit of time. era = A unit of time shorter than an eon but longer than a period. period = A unit of time shorter than an era but longer than epoch. epoch = A unit of time shorter than a period but longer than an age. Archean = “Ancient” eon from 4,500 Mya – 2,500 Ma.
What is eons in geologic time scale?
eon, Long span of geologic time. In formal usage, eons are the longest portions of geologic time (eras are the second-longest). Three eons are recognized: the Phanerozoic Eon (dating from the present back to the beginning of the Cambrian Period), the Proterozoic Eon, and the Archean Eon.
How long is geologic period?
Period: This is the basic unit of geologic time. A Period lasts tens of millions of years, which is the time it takes to form one type of rock system.
What are the 3 eras of geologic time?
The Phanerozoic Eon is divided into three eras, the Paleozoic, Mesozoic and Cenozoic eras. These were named for the kinds of fossils that were present. The Cenozoic is the youngest era and the name means “new life”.
What is a geologic time period?
geologic time, the extensive interval of time occupied by the geologic history of Earth. Geologic time is, in effect, that segment of Earth history that is represented by and recorded in the planet’s rock strata.
How long is a period geologic time?
Terminology
| Segments of rock (strata) in chronostratigraphy | Time spans in geochronology | Notes to geochronological units |
|---|---|---|
| Erathem | Era | 10 defined, several hundred million years |
| System | Period | 22 defined, tens to ~one hundred million years |
| Series | Epoch | 34 defined, tens of millions of years |
| Stage | Age | 99 defined, millions of years |
How are geological time periods determined?
The geologic time scale was constructed to visually show the duration of each time unit. This was done by making a linear time line on the left side of the time columns. Thicker units such as thee Proterozoic were longer in duration than thinner units such as the Cenozoic.
