Geologic time scale

The geologic time scale is a stratigraphic table showing the geological history chronologically and hierarchically. With the beginning of the Phanerozoic ( the "Age of visible ( animal ) life" ) 542 million years ago is a continuous fossil record, which allows using the methods of biostratigraphy a more differentiated classification.

In geological tables are the older time periods below ( Lying ), the younger above ( hanging wall ) are just as the series of sedimentary rocks found within an idealized, tectonically undisturbed rock profile. Other representations do not meet the international standard.

A binding international division of the geologic time scale is carried out by the International Commission on Stratigraphy (ICS ). The table to the right shows the era after ICS standard in compact overview. It is not complete ( the division into series and stages missing) and not commented. A detailed table can be found here.

• 2.1 Limits of age determination
• 2.2 Role of the atmosphere
• 2.3 Role of Fossils
• 2.4 Paläobotanik

• 4.1 Comparison era - A Day
• 4.2 Comparison with the United Nations building in New York

• 5.1 tertiary
• 5.2 Quaternary

International Tables standards

Eon, era, period, epoch, age

The geological history spanning a vast period of time, which is divided into hierarchically structured time intervals:

• Aeon ( eon german, big αἰών Aion "eternity" ) Era, geological era (English era, mlat. Aera " age" ), also known as age group or simplistic Period ( engl. period, large περίοδος periodos " repeating section" ) Epoch (English epoch, large ἐποχή epoch " breakpoint " ) Age ( engl. age)

The time intervals can be structured by further subcategories. Thus the period of carbon in the sub-periods Pennsylvanian (Upper Carboniferous) and Mississippian example, is divided (Lower Carboniferous).

Historically evolved from names of rock units, the designation of the time intervals. For example, originate Devonian rocks from the time interval Devon. Sometimes you have to distinguish whether abstract, absolute time intervals are meant or time intervals, which were deduced from rock strata. Depending on different designations for the above categories used, for example: aeon (absolute) - Äonothem ( rock related), epoch (absolute) - series ( rock related). See geochronology and chronostratigraphy.

Different tables

Some slightly different tables of the geological time scale worldwide are currently used:

• The Table of the International Commission on Stratigraphy (ICS )
• The international benchmark scale of the Geological Society of America ( GSA)
• The Table of the Commission de la Carte du Monde Géologique ( CCGM ), Paris

In different tables can be different:

• The names of the time intervals, which are often selected according to locally occurring rocks or fossils. For the same period there may be different names, such as for the cold periods in the Alps (eg Günz cold period ) and in Northern Germany (Elbe glacial period ).
• Information at the beginning and end of the time intervals in mya. So the beginning of the Cambrian is mya in different tables, for example, 540, 542 mya specified or 570 mya. Modern tables are based partly improved methods of age determination.
• The ranking of individual sections within the hierarchy. So Paleogene and Neogene are " ascended " in the hierarchy, where the Neogene (recently one period) contains his former followers now as epochs.

But the different tables are always together:

• The absolute time information ( in mya ) in relation to a fossil, as its age can be determined on the rock. In such an age, the tables are therefore equivalent (see also age determination: Archaeology ).

History of geological scales

In the 17th century it was known by the work of Nicolaus Steno that different rock layers represent different periods of Earth's history, but there was no method to date them or assign. Fossil record of marine life in the high mountains were also early to the conclusion that the earth is not immutable, but profound changes is subjected. Therefore, this knowledge had been strange, because the geological periods have been vastly underestimated. One way of absolute age determination did not exist. Also mistakenly was assumed that finds a rock would have to be created each time. The problem was raised by numerous scientists over again, including the British geologist William Smith and Charles Lyell.

Today, the age of the earth and the acting geological processes are well known and recognized, but the exact sequence of the geological development is incompletely understood. There are only shadowy knowledge about the particular long time before the appearance of the first fossils.

First graphical representations created by recorded the sequence of rock layers together individuals and led such representations in a table. Even modern scales follow this tradition, the structure of the tables is now set by organizations. Their members shall agree in accordance with specified criteria on a consensus.

In addition to the tables today there are also maps of the world to the different ages. For this tableau form of the earth's history, there is currently no standardized or generally accepted version.

Comments

Boundaries of age determination

The ages and periods of the Phanerozoic are now classified based on fossils, especially, the age of the rocks is determined by radiochemical methods and thus the age of the fossils is established (see also age determination). Rocks older periods can only associate with geophysical methods that can shed light on the development in the Proterozoic and Archean increasingly. Largely unknown are the events in the Hadean, mainly because hardly any are still present rocks from this period. Since that time, occurring exogenous and endogenous geological upheavals of the earth's crust have removed a lot of the time created sculptures or pushed down in great depth.

Role of the atmosphere

There is growing recognition that the Earth's atmosphere is an important factor in Earth's history. She was composed differently at different epochs, which was accompanied mutually with the evolution of the living world. In particular their composition in ancient geological periods is still unclear today. It is certain that atmospheric oxygen is a direct result of the development and life would not exist without living beings. Various sedimentary rocks that now occur in great numbers, only ever could therefore arise (eg limestone ).

Role of fossils

Wild life has greatly influenced the geological face of the earth. Life has developed relatively quickly after the formation of the Earth and taken all offered to him habitats. In the so-called Cambrian explosion, there was a sudden increase of living organisms in the fossil record. Since then, almost every corner of the Earth's surface is alive - the biomass was added to a surface feature of our planet. For the dating of rock layers, the index fossils are crucial.

Paleobotany

In the Paläobotanik the ending- phytikum is used instead of suffix- zoikum. The Paleozoic is in botany divided into Palaeophytic ( Silurian to Permian) and Eophytikum ( Cambrian and Ordovician ).

Since the Neophytikum ( = Känophytikum ) took 95 million years and the Neozoikum ( = Cenozoic ) 65 million years, the boundaries are shifted against each other.

Time scale with enlarged cutouts

The Phanerozoic is as the age of the fossils of particular interest. Here, the classification becomes more accurate, the periods are shorter. This is especially true for the Cenozoic, ie the period since the mass extinction of the dinosaurs. So here's a representation with enlarged cutouts.

Illustrate the periods

The geological era include enormous periods of time that are hard to measure. This misunderstanding may arise, for example, the opinion, for the entire evolution had not been enough time. The following comparisons are used to illustrate the periods.

Compare era - A Day

If the Earth were a day old, so there would be people for only a few seconds.

Comparison with the UN building in New York

It is 40 stories high. Each floor would correspond here 100 million years.

(*) Suppose, on the roof of the building would be a book of 500 pages, which would correspond to the age of mankind, then would describe the time since the birth of Christ, the last page of the book.

Earlier classification of the Cenozoic

The Ärathem of the Cenozoic was formerly divided into the Tertiary and Quaternary. Meanwhile, the Tertiary is of the International Commission on Stratigraphy in the geological time scale ( Geologic Time Scale 2004) no longer used. Today, the Cenozoic in Paleogene, Neogene and Quaternary is divided.

The term " tertiary " ( 66 to 1.806 Ma) comes from the fact that Europe's former geologist greatly overestimated this period because of the very powerful sediments ( about 200 years ago). So he was placed as third epoch of Earth's history the meso-and Paleozoic to the side.

Because of the wide disparity in the heavily populated basins thick sediment layers and because of alpidischen orogeny you divided the Tertiary very diverse:

• Paleogene with Paleocene, Eocene and Oligocene ( and each further subdivisions in accordance with regional stratigraphic aspects )
• Neogene ( " newly created ") with the Miocene and the Pliocene ( and each further subdivisions in accordance with regional stratigraphic aspects )

The name of the Quaternary ( 2,588 Ma to present) means " Fourth Earth Poche " - reasoning as above.

• Pleistocene ( four major ice ages and three interglacial periods )
• Holocene ( geologic presence since about 11,000 years ago )

Some geologists a newest era is suggested that the Anthropocene ( since 1800 ).