Historical geology focuses on geological processes that change the surface of the earth and its 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 at 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 obtaining the absolute and relative age of geological history.
Economic geology, the search and extraction of fuel and raw materials are largely dependent on an understanding of the history of a particular area. Environmental geology, including determining the geological hazard of earthquakes and volcanic eruptions, should also include 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 living organisms.
James Hatton and Charles Lyell also contributed to an early understanding of Earth history. Hatton first proposed the theory of uniformitarianism, which is now the main principle in all areas of geology. Hatton also supported the idea that the Earth is quite ancient, in contrast to the prevailing concept of the time, which stated that the Earth numbered only a few millennia of its existence. Uniformatism describes the Earth, created by the same natural phenomena that operate today.
Discipline history
The predominant concept of the 18th century in the West was the belief that various catastrophic events prevailed in a very short history of the Earth. 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 disputes and discussions throughout the 19th century. Many discoveries in the 20th century gave enough evidence that the history of the Earth is the product of both gradual incremental processes and sudden cataclysms. Now these beliefs are the foundations of historical geology. Catastrophic events, such as falling meteorites and large volcanic explosions, form the Earth's surface along with gradual processes such as weathering, erosion and precipitation. The present is the key to the past and includes both catastrophic and gradual processes, which allows us to understand the engineering geology of historical territories.
Geological timeline
A geological time scale is a chronological dating system that links geological layers (stratigraphy) with specific time intervals. Without a basic understanding of this scale, a person hardly understands that he is studying historical geology. This scale is used by geologists, paleontologists and other scientists to determine 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 time division are the eons successively following one after another: Hadean, Archean, Proterozoa and Phaneroza. Eons are divided into eras, which, in turn, are divided into periods, and periods into eras.
In accordance with aeons, eras, periods and epochs, the terms “anonym”, “eratem”, “system”, “series”, “stage” are used to designate layers of rock that belong to these sections of geological time in the history of the Earth.
Geologists qualify these units as “early”, “middle” and “late” when it comes to time, and “lower”, “middle” and “upper” when it comes to corresponding stones. For example, the Lower Jurassic deposits in chronostratigraphy correspond to the early Jurassic era in geochronology.
Earth history and age
Radiometric dating indicates that the Earth is about 4.54 billion years old. Different time intervals on the geological timeline are usually marked by corresponding changes in the composition of the strata, which indicate major geological or paleontological events, such as mass extinctions. For example, the boundary between the Cretaceous period and the Paleogene period is determined by the Cretaceous-Paleogenic extinction, which marked the death of dinosaurs and many other groups of life.
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 the basics of paleontology and astronomy
Some other planets and satellites of the solar system have sufficiently rigid structures to keep records of their own stories, for example, Venus, Mars and the Moon. Dominant planets, such as gas giants, do not preserve their history in a comparable way. In addition to massive bombardments by meteorites, events on other planets probably had little effect on the Earth, and events on Earth, respectively, had little effect on these planets. Thus, the construction of a timeline that connects planets is only of limited value for the Earth's timeline, with the exception of the context of the solar system. The prospects for the historical geology of other planets - astropaleogeology - are still being debated by scientists.
The discovery of Nikolai Steno
At the end of the XVII century, Nikolai Steno (1638-1686) formulated the principles of the geological history of the Earth. The Wall claimed that rock layers (or strata) were laid sequentially, and each of them is a “slice” of time. He also formulated the law of superposition, which states that any single layer is probably older than those above it and younger than those below it. Although the principles of Steno were simple, their application was 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:
- Sequence of layers often undergo erosion, distortion, tilt, or even inversion.
- Strata, laid at the same time in different areas, can have a completely different structure.
- Strata of any area are only part of the long history of the Earth.
James Hatton and Plutonism
The theories of the Neptunists, popular at that time (set forth by Abraham Werner (1749-1817) at the end of the 18th century), boiled down to the fact that all the stones and rocks originate from some kind of huge flood. A big shift in thinking occurred when James Hutton presented his theory to 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. Hatton suggested that it was very hot inside the Earth and that this heat was the engine that prompted the creation of new stones and rocks. Then the Earth was cooled by air and water, settled in the form of seas - which, for example, is partially confirmed by the historical geology of the sea over the Urals. This theory, known as "Plutonism", was very different from the "Neptunistic" theory based on the study of water flows.
The discovery of other foundations of historical geology
The first serious attempts to formulate a geological time scale that can be applied anywhere in the world were made at the end of the 18th century. The most successful of those early attempts (including Werner) divided the rocks of the earth's crust into four types: primary, secondary, tertiary and quaternary. Each type of rock, according to theory, formed during a certain period in the history of the Earth. Thus, it was possible to talk about the "Tertiary period", as well as about the "Tertiary breeds". Indeed, the term “tertiary” (currently Paleogene and Neogene) is still often used as the name of the geological period that began after the extinction of dinosaurs, and the term “Quaternary” remains the formal name of the current period. Practical tasks in historical geology were given to cabinet theoreticians very quickly, because everything that they thought of themselves had to be proved in practice - as a rule, through long excavations.
Deposits
The identification of strata by the fossils contained in them, first proposed by William Smith, Georges Cuvier, Jean d'Amalius d'Allach and Alexander Bronnart at the beginning of the 19th century, allowed geologists to more accurately divide the history of the Earth. It also allowed them to compare layers along national (or even continental) borders. If two strata contained the same fossils, then they were laid at the same time. Historical and regional geology rendered overwhelming help in making this discovery.
Names of geological periods
In the early work on the development of the geological time scale, British geologists dominated, and the names of the geological periods reflect this dominance. “Cambrian” (the classic name for Wales), “Ordovician” and “Silurian”, named after the ancient Welsh tribes, were periods identified using stratigraphic sequences from Wales. “Devon” was named after the English county of Devonshire, and “Carbon” was named after the obsolete coal measures used by 19th century British geologists. The Perm period was named after the Russian city of Perm, because it was identified using strata in this region by the Scottish geologist Roderick Murchison.
However, some periods were determined by geologists from other countries. The Triassic period was named in 1834 by the German geologist Friedrich Von Alberti from three different layers (trias in Latin "triad"). The Jurassic period was named by the French geologist Alexander Bronnyart in honor of the vast marine limestone rocks of the Jurassic Mountains. The Cretaceous period (from the Latin creta, which translates as "chalk") was first identified by the Belgian geologist Jean d'Omalius d'Halloy in 1822 after studying the Cretaceous deposits (calcium carbonate precipitated by shells of marine invertebrates) found in Western Europe.
Separation of eras
British geologists also first introduced the sorting of periods and their division into eras. In 1841, John Phillips published the first global geological timeline based on the types of fossils discovered in each era. The Phillips scale helped standardize the use of terms such as the Paleozoic (“old life”), which he extended for a longer period than in the previous use, and the Mesozoic (“middle life”), which he independently invented. Those who are still interested in learning about this wonderful science that studies the history of the earth, but don’t have time to read Phillips, Steno and Hatton, can be advised by Koronovsky’s “Historical Geology”.