What is the Geological Time Scale?

The geological time scale breaks down the history of the earth into time zones marked by different events, species and evolution of the species. Earth scientists such as geologists and paleontologists use the geological time scale to explain the times and associations of events that took place in the history of the earth.

Formulation of the geological time scale

The first significant attempt to construct a geological time scale applicable anywhere on earth was made towards the end of the 18th century. Werner supported the most significant attempt. William Smith, Jean d’Omlius d’Halloy, Georges Cuvier and Alexandre Brogniart made efforts to identify the strata using the fossils they contained in the early 19th century. These efforts have made it easier for geologists to create more precise divisions in the history of the earth. The correlation between cross-border and continental layers became possible. Two layers that contained the same fossil were considered to be spread over the same period regardless of how far apart the layers were located. A detailed study of the stratification and fossils of Europe was conducted between 1820 and 1850.

Geological table

The geological table was constructed by terrestrial geologists based on how layers and fossils were placed in the earth’s crust. Before radioactivity was discovered in 1896 and radiometric dating was developed, geologists estimated the times by studying erosion rates, weathering and sedimentation. In 1913, Arthur Holmes, a British geologist, published the first geological time scale with absolute dates. The geologist is also credited with promoting the discipline of geochronology and the publication of “The Age of Earth”, a world-renowned book that states that the earth is at least 1.6 billion years old.

Eras of the Geologic Time Scale

The geological time scale has four periods, the first being the Precambrian era, followed by the Paleozoic era, the Mesozoic era and the Cenozoic era.

It was Precambrian

The Precambrian era dates from the beginning of the earth to around 4.6 billion years ago. There was no life on earth during the Precambrian era.

Paleozoic era

The next time is the Palaeozoic era dating back to 542 million years ago to 250 million years ago. Many species developed during this era, but most were wiped out before the end of time.

Mesozoic era

The Mesozoic era followed the Paleozoic era. The period dated between 250 and 65 million years ago. Many species evolved during the Mesozoic era to replace those that became extinct in the previous era. The humid and tropical climate of the Mesozoic era leads to the growth of many types of plants. Another incident that marks the Mesozoic period is the evolution of dinosaurs into birds. Towards the end of this era, another great extermination of the species including the dinosaurs took place.

It was Cenozoic

The small mammals that survived the Mesozoic era prospered during the Cenozoic era. This period dates back to about 65 million years ago to the present day. Human evolution occurred during this time frame, and all life on earth evolved from their previous primitive states to their current states in the Cenozoic era.

Denomination of periods, epochs and geological eras

British geologists dominated the early stages of geological time scale developments. The influence of these geologists is evident in the names of geological periods such as the Cambrian, the Ordovician and the Silurian. The periods were named after the Welsh tribes and were defined using the strata formation sequence in Wales. Other periods with this influence include the Devonian which takes its name from the County of Devon and the Carboniferous adapted from the name of the British geologist for the layers “measures of coal”. However, geologists from other countries have defined certain periods. A good example is the “Triassic” named by Friedrich Von Alberti, a German geologist. The “Jurassic”, on the other hand, was appointed by a French geologist Alexandre Brogniart.

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