Historical geology focuses on the geological processes that change the Earth's surface and appearance. It uses stratigraphy, structural geology, and paleontology to determine the sequence of these events. It also focuses on the evolution of plants and animals over different time periods on a geological scale. The discovery of radioactivity and the development of several radiometric dating methods in the first half of the 20th century provided a means of deriving the absolute and relative ages of geological history.
Economic geology, the search for and extraction of fuels and raw materials largely depend on understanding the history of a particular area. Environmental geology, including determining the geological hazard of earthquakes and volcanic eruptions, must also include a detailed knowledge of geological history.
Founding Scientists
Nikolai Steno, also known as Niels Stensen, was the first to observe and propose some of the basic concepts of historical geology. One of these concepts was that fossils originally came from livingorganisms.
James Hutton and Charles Lyell also contributed to the early understanding of Earth's history. Hutton first proposed the theory of uniformitarianism, which is now a basic principle in all areas of geology. Hutton also supported the idea that the Earth was quite ancient, as opposed to the prevailing concept of the time, which said that the Earth was only a few thousand years old. Uniformism describes the Earth as created by the same natural phenomena that are at work today.
History of the discipline
The prevailing concept in the 18th century in the West was the belief that various cataclysmic events dominated the Earth's very short history. This view was strongly supported by adherents of Abrahamic religions based on a largely literal interpretation of religious biblical texts. The concept of uniformitarianism met with considerable resistance and led to controversy and debate throughout the 19th century. A plethora of discoveries in the 20th century provided ample evidence that Earth's history is the product of both gradual incremental processes and sudden cataclysms. These beliefs are now the foundations of historical geology. Catastrophic events such as meteorite impacts and large volcanic explosions shape the Earth's surface along with gradual processes such as weathering, erosion and sedimentation. The present is the key to the past and includes both catastrophic and gradual processes, which makes us understand the engineeringgeology of historical territories.
Geological time scale
The geological time scale is a chronological dating system that links geological layers (stratigraphy) to specific time intervals. Without a basic understanding of this scale, a person will hardly understand what historical geology studies. This scale is used by geologists, paleontologists, and other scientists to define and describe various periods and events in the history of the earth. In essence, modern historical geology is based on it. The table of geological time intervals presented on the scale is consistent with the nomenclature, dates and standard color codes established by the International Commission on Stratigraphy.
The primary and largest units of division of time are eons, successively following each other: Hadean, Archean, Proterozoic and Phanerozoic. Eons are divided into eras, which, in turn, are divided into periods, and periods are divided into epochs.
According to eons, eras, periods and epochs, the terms "anonymous", "eratem", "system", "series", "stage" are used to designate the rock layers that belong to these sections of geological time in history Earth.
Geologists classify these units as "early", "middle" and "late" when referring to time, and "lower", "middle" and "upper" when referring to the corresponding rocks. For example, the Lower Jurassic in chronostratigraphy corresponds to the early Jurassic in geochronology.
History and age of the Earth
Radiometric dating data indicate that the Earth is about 4.54 billion years old. Different spans of time on the geologic time scale are usually marked by corresponding changes in strata composition that indicate major geological or paleontological events such as mass extinctions. For example, the boundary between the Cretaceous and the Paleogene is defined by the Cretaceous-Paleogene extinction event, which marked the end of the dinosaurs and many other life groups.
Geological units from the same time but in different parts of the world often look different and contain different fossils, so deposits belonging to the same time period have historically been given different names in different places.
Historical geology with basic paleontology and astronomy
Some other planets and moons in the solar system have rigid enough structures to keep records of their own histories, such as Venus, Mars and the Moon. Dominant planets such as the gas giants do not retain their history in a comparable way. Other than massive meteorite bombardments, events on other planets probably had little effect on Earth, and events on Earth had correspondingly little effect on those planets. Thus, constructing a time scale that links the planets is of only limited value to the Earth's time scale, except in the context of the solar system. Perspectives on the historical geology of other planets - astropaleogeology - are still being debatedscientists.
Discovery of Nikolai Steno
At the end of the 17th century, Nikolai Steno (1638-1686) formulated the principles of the geological history of the Earth. Steno argued that the layers of rocks (or strata) were laid down sequentially, and each of them represents a "slice" of time. He also formulated the law of superposition, which states that any given layer is likely to be older than those above it and younger than those below it. Although Steno's principles were simple, their application proved difficult. Steno's ideas also led to the discovery of other important concepts that even modern geologists use. During the 18th century, geologists realized that:
- Layer sequences are often eroded, distorted, tilted or even inverted.
- Strats laid at the same time in different areas can have completely different structures.
- The strata of any given region are only part of Earth's long history.
James Hutton and Plutonism
The Neptunist theories popular at the time (set out by Abraham Werner (1749-1817) at the end of the 18th century) were that all rocks and rocks originated from some huge flood. A great shift in thinking occurred when James Hutton presented his theory before the Royal Society of Edinburgh in March and April 1785. John McPhee later claimed that James Hutton became the founder of modern geology that very day. Hutton suggested that the interior of the Earth is very hot, and that it is warmwas the engine that encouraged the creation of new stones and rocks. Then the Earth was cooled by air and water, which settled in the form of seas - which, for example, is partly confirmed by the historical geology of the sea over the Urals. This theory, known as "Plutonism", was very different from the "Neptunian" theory based on the study of water flows.
Discovery of other foundations of historical geology
The first serious attempts to formulate a geological time scale that can be applied anywhere on Earth were made at the end of the 18th century. The most successful of those early attempts (including Werner's) divided the rocks of the earth's crust into four types: primary, secondary, tertiary, and quaternary. Each type of rock, according to the theory, formed during a certain period in the history of the Earth. Thus, one could speak of a "Tertiary period" as well as "Tertiary rocks". Indeed, the term "Tertiary" (now Paleogene and Neogene) is still often used as the name of the geological period after the extinction of the dinosaurs, and the term "Quaternary" remains the formal name of the current period. Practical problems in historical geology were provided to armchair theorists very quickly, because everything they thought of on their own had to be proved in practice - as a rule, through long excavations.
Fossil content in sediments
Identification of strata by their fossils, first proposed by William Smith, Georges Cuvier, Jean d'Amalius d'Allah andAlexander Bronnart in the early 19th century allowed geologists to more accurately divide the history of the Earth. It also allowed them to map layers along national (or even continental) boundaries. If two strata contained the same fossils, then they were deposited at the same time. Historical and regional geology have provided overwhelming assistance in making this discovery.
Names of geological periods
Early work on the development of the geologic time scale was dominated by British geologists, and the names of the geologic periods reflect this dominance. "Cambrian" (the classical name for Wales), "Ordovician" and "Silur", named after ancient Welsh tribes, were periods defined using stratigraphic sequences from Wales. "Devon" was named after the English county of Devonshire, while "Carbon" was named after the obsolete coal measures used by 19th century British geologists. The Permian was named after the Russian city of Perm because it was defined using strata in that region by Scottish geologist Roderick Murchison.
However, some periods have been determined by geologists from other countries. The Triassic period was named in 1834 by the German geologist Friedrich von Alberti from three distinct layers (trias is Latin for "triad"). The Jurassic period was named by the French geologist Alexandre Bronnjart after the vast marine limestone rocks of the Jura Mountains. Cretaceous period (from the Latin creta, whichtranslated as "chalk") was first identified by the Belgian geologist Jean d'Omalius d'Halloy in 1822 after studying chalk deposits (calcium carbonate deposited by the shells of marine invertebrates) found in Western Europe.
Split epochs
British geologists also pioneered the sorting of periods and their division into epochs. In 1841, John Phillips published the first global geological time scale based on the types of fossils found in each era. The Phillips scale helped standardize the use of terms such as Paleozoic ("old life"), which he extended to a longer period than previous usage, and Mesozoic ("middle life"), which he invented on his own. For those who are still interested in learning about this wonderful science of the history of the earth, but do not have time to read Phillips, Steno and Hutton, we can advise Koronovsky's Historical Geology.
