Union
Well-Known Member
OMG , I forgot about the 2 periods about the creation of the earth ......
Geologic Time scale
Eons and Eras
The first principal subdivision is called the eon. An eon, the largest division of the geologic time scale, spans hundreds to thousands of millions of years. Geologists generally agree that there are two major eons: the Precambrian eon and the Phanerozoic eon. The Precambrian goes from the formation of the earth to the time when multicellular organisms first appeared - that's a really long time - from 4,500 million years ago to just about 543 million years ago. Then begins the Phanerozoic eon, which continues up to today.
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.
Keep in mind that these three eras are all grouped within the Phanerozoic eon. Remember that other eon, the Precambrian eon? Well, that one doesn't get to have any eras inside it. We don't have a lot of information....
http://earthsurfaceprocesses.com/3c-E-MassExtn.html
http://imnh.isu.edu/exhibits/online/geo_time/geo_time_eons.htm
The Structure of Geologic Time
http://geology.com/time.htm
Geologic Time Scale
A Time Line for the Geological Sciences
Dividing Earth History into Time Intervals
Geologists have divided Earth's history into a series of time intervals. These time intervals are not equal in length like the hours in a day. Instead the time intervals are variable in length. This is because geologic time is divided using significant events in the history of the Earth.
Examples of Boundary "Events"
For example, the boundary between the Permian and Triassic is marked by a global extinction in which a large percentage of Earth's plant and animal species were eliminated. Another example is the boundary between the Precambrian and the Paleozoic which is marked by the first appearance of animals with hard parts.
Eons
are the largest intervals of geologic time and are hundreds of millions of years in duration. In the time scale above you can see the Phanerozoic Eon is the most recent eon and began more than 500 million years ago......
Geologic Time scale
Eons and Eras
The first principal subdivision is called the eon. An eon, the largest division of the geologic time scale, spans hundreds to thousands of millions of years. Geologists generally agree that there are two major eons: the Precambrian eon and the Phanerozoic eon. The Precambrian goes from the formation of the earth to the time when multicellular organisms first appeared - that's a really long time - from 4,500 million years ago to just about 543 million years ago. Then begins the Phanerozoic eon, which continues up to today.
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.
Keep in mind that these three eras are all grouped within the Phanerozoic eon. Remember that other eon, the Precambrian eon? Well, that one doesn't get to have any eras inside it. We don't have a lot of information....
http://earthsurfaceprocesses.com/3c-E-MassExtn.html
http://imnh.isu.edu/exhibits/online/geo_time/geo_time_eons.htm
The Structure of Geologic Time
http://geology.com/time.htm
Geologic Time Scale
A Time Line for the Geological Sciences
Dividing Earth History into Time Intervals
Geologists have divided Earth's history into a series of time intervals. These time intervals are not equal in length like the hours in a day. Instead the time intervals are variable in length. This is because geologic time is divided using significant events in the history of the Earth.
Examples of Boundary "Events"
For example, the boundary between the Permian and Triassic is marked by a global extinction in which a large percentage of Earth's plant and animal species were eliminated. Another example is the boundary between the Precambrian and the Paleozoic which is marked by the first appearance of animals with hard parts.
Eons
are the largest intervals of geologic time and are hundreds of millions of years in duration. In the time scale above you can see the Phanerozoic Eon is the most recent eon and began more than 500 million years ago......