According to modern ideas of scientists, the geological history of our planet is 4.5-5 billion years. In the process of its development, it is customary to single out the geological periods of the Earth.
General information
Geological periods of the Earth (table below) are a sequence of events that have occurred in the process of the planet's development since the formation of the earth's crust on it. Over time, various processes take place on the surface, such as the emergence and destruction of landforms, submersion of land areas under water and raising them, glaciation, as well as the appearance and disappearance of various species of plants and animals, etc. Our planet bears obvious traces of his education. Scientists claim that they are able to fix them with mathematical accuracy in various layers of rocks.
Main sediment groups
Geologists, trying to reconstruct the history of the planet, are studying rock layers. It is customary to divide these deposits into five main groups, distinguishing the following geological eras of the Earth: the most ancient (Archaean), early (Proterozoic), ancient (Paleozoic), middle (Mesozoic) and new (Cenozoic). It is believed thatthe boundary between them runs along the largest evolutionary phenomena that have occurred on our planet. The last three eras, in turn, are divided into periods, since the remains of plants and animals are most clearly preserved in these deposits. Each stage is characterized by events that have had a decisive influence on the current relief of the Earth.
Ancient stage
The Archean era of the Earth was distinguished by quite violent volcanic processes, as a result of which igneous granite rocks appeared on the surface of the planet - the basis for the formation of continental plates. At that time, only microorganisms existed here that could do without oxygen. It is assumed that deposits of the Archean era cover certain areas of the continents with an almost solid shield, they contain a lot of iron, silver, platinum, gold and ores of other metals.
Early Stage
The Proterozoic era is also characterized by high volcanic activity. During this period, mountain ranges of the so-called Baikal folding were formed. To this day, they have practically not survived, today they are just separate insignificant uplifts on the plains. During this period, the Earth was inhabited by the simplest microorganisms and blue-green algae, the first multicellular organisms appeared. The Proterozoic rock formation is rich in minerals: mica, non-ferrous metal ores and iron ores.
Ancient stage
The first period of the Paleozoic era was marked by the formation of mountain ranges of the Caledonian folding. This led toa significant reduction in marine basins, as well as the emergence of huge land areas. Separate ranges of that period have survived to this day: in the Urals, in Arabia, Southeast China and Central Europe. All these mountains are "worn out" and low. The second half of the Paleozoic is also characterized by mountain building processes. Here the ridges of the Hercynian folding were formed. This era was more powerful, vast mountain ranges arose in the territories of the Urals and Western Siberia, Manchuria and Mongolia, Central Europe, as well as Australia and North America. Today they are represented by very low blocky massifs. Animals of the Paleozoic era are reptiles and amphibians, the seas and oceans are inhabited by fish. Among the flora, algae predominated. The Paleozoic era (Carboniferous period) is characterized by large deposits of coal and oil, which arose precisely in this era.
Middle Stage
The beginning of the Mesozoic era is characterized by a period of relative calm and the gradual destruction of the mountain systems created earlier, submersion of flat territories (part of Western Siberia) under water. The second half of this period was marked by the formation of Mesozoic folding ridges. Very vast mountainous countries appeared, which today have the same appearance. As an example, we can cite the mountains of Eastern Siberia, the Cordillera, certain parts of Indochina and Tibet. The ground was densely covered with lush vegetation, which gradually died off and rotted away. Due to the hot and humid climate, active formation of peatlands andswamps. It was the era of giant lizards - dinosaurs. The inhabitants of the Mesozoic era (herbivores and predatory animals) spread throughout the entire planet. At the same time, the first mammals appear.
New stage
The Cenozoic era, which replaced the middle stage, continues to this day. The beginning of this period was marked by an increase in the activity of the internal forces of the planet, which led to a general uplift of huge areas of land. This era is characterized by the emergence of mountain ranges of Alpine folding within the Alpine-Himalayan belt. During this period, the Eurasian continent acquired its modern shape. In addition, there was a significant rejuvenation of the ancient massifs of the Urals, Tien Shan, Appalachians and Altai. The climate on Earth changed dramatically, periods of powerful ice cover began. Movements of glacial masses changed the relief of the continents of the Northern Hemisphere. As a result, hilly plains with a huge number of lakes were formed. Animals of the Cenozoic era are mammals, reptiles and amphibians, many representatives of the initial periods have survived to this day, others have become extinct (mammoths, woolly rhinos, saber-toothed tigers, cave bears and others) for one reason or another.
What is a geological period?
The geological stage as a unit of the geochronological scale of our planet is usually divided into periods. Let's see what the encyclopedia says about this term. Period (geological) is a large interval of geological time during which rocks were formed. In turn, hesubdivided into smaller units, which are commonly called epochs.
The first stages (Archaean and Proterozoic) due to the complete absence or insignificant amount of animal and vegetable deposits in them, it is not customary to divide into additional sections. The Paleozoic era includes the Cambrian, Ordovician, Silurian, Devonian, Carboniferous and Permian periods. This stage is characterized by the largest number of subintervals, the rest were limited to only three. The Mesozoic era includes the Triassic, Jurassic and Cretaceous stages. The Cenozoic era, the periods of which are most studied, is represented by the Paleogene, Neogene and Quaternary subinterval. Let's take a closer look at some of them.
Triassic
The Triassic period is the first subinterval of the Mesozoic era. Its duration was about 50 million years (beginning - 251-199 million years ago). It is characterized by the renewal of marine and terrestrial fauna. At the same time, a few representatives of the Paleozoic continue to exist, such as spiriferides, tabulates, some laminabranchs, and others. Among the invertebrates, ammonites are very numerous, giving rise to many new forms important for stratigraphy. Among corals, six-rayed forms predominate, among brachiopods - terebratulids and rhynchonelids, in the group of echinoderms - sea urchins. Vertebrate animals are mainly represented by reptiles - large lizard dinosaurs. Thecodonts are widespread land reptiles. In addition, the first large inhabitants of the aquatic environment appear in the Triassic period - ichthyosaurs andplesiosaurs, however, they reach their heyday only in the Jurassic period. Also at this time, the first mammals arose, which were represented by small forms.
Flora in the Triassic period (geological) loses Paleozoic elements and acquires exclusively Mesozoic composition. Fern species of plants, sago-like, coniferous and ginkgoales predominate here. Climatic conditions are characterized by significant warming. This leads to the drying up of many inland seas, and in the remaining seas the level of salinity increases significantly. In addition, the areas of inland water bodies are greatly reduced, resulting in the development of desert landscapes. For example, the Tauride Formation of the Crimean Peninsula is attributed to this period.
Yura
The Jurassic Period got its name from the Jurassic Mountains in Western Europe. It constitutes the middle part of the Mesozoic and most closely reflects the main features of the development of the organics of this era. In turn, it is customary to divide it into three sections: lower, middle and upper.
The fauna of this period is represented by widespread invertebrates - cephalopods (ammonites, represented by numerous species and genera). They sharply differ from representatives of the Triassic in sculpture and character of shells. In addition, in the Jurassic period, another group of mollusks, the belemnites, flourished. At this time, six-ray reef-building corals, sea sponges, lilies and urchins, as well as numerous lamellar gills, reach significant development. Butspecies of the Paleozoic brachiopod completely disappear. The marine fauna of vertebrate species is significantly different from the Triassic, it reaches an enormous diversity. In the Jurassic, fish are widely developed, as well as aquatic reptiles - ichthyosaurs and plesiosaurs. At this time, there is a transition from land and adaptation to the marine environment of crocodiles and turtles. A huge variety is achieved by various types of terrestrial vertebrates - reptiles. Among them, dinosaurs come to their heyday, which are represented by herbivores, carnivores and other forms. Most of them reach 23 meters in length, for example, diplodocus. In the sediments of this period, a new type of reptile is found - flying lizards, which are called "pterodactyls". At the same time, the first birds appear. The flora of the Jura reaches a luxuriant flowering: gymnosperms, ginkgos, cycads, conifers (araucaria), bennettites, cycads and, of course, ferns, horsetails and club mosses.
Neogene
The Neogene period is the second period of the Cenozoic era. It began 25 million years ago and ended 1.8 million years ago. Significant changes in the composition of the fauna took place at this time. A wide variety of gastropods and bivalves, corals, foraminifers, and coccolithophores emerge. Amphibians, sea turtles and bony fishes have been widely developed. In the Neogene period, terrestrial vertebrate forms also reach great diversity. For example, rapidly progressing hipparion species appeared: hipparions, horses, rhinos, antelopes, camels, proboscis, deer,hippos, giraffes, rodents, saber-toothed tigers, hyenas, great apes and others.
Under the influence of various factors, the organic world is rapidly evolving at this time: forest-steppes, taiga, mountain and plain steppes appear. In tropical areas - savannahs and wet forests. Climatic conditions are approaching modern.
Geology as a science
Geological periods of the Earth are studied by science - geology. It appeared relatively recently - at the beginning of the 20th century. However, despite her youth, she was able to shed light on many controversial issues about the formation of our planet, as well as the origin of the creatures inhabiting it. There are few hypotheses in this science, mainly only the results of observations and facts are used. There is no doubt that the traces of the development of the planet stored in the earth's layers will in any case give a more accurate picture of the past than any written book. However, not everyone is able to read these facts and understand them correctly, therefore, even in this exact science, erroneous interpretations of certain events can occur from time to time. Where traces of fire are present, it is safe to say that there was fire; and where there are traces of water, with the same certainty it can be argued that there was water, and so on. And yet, mistakes also happen. In order not to be unfounded, consider one such example.
Frost patterns on glasses
In 1973, the magazine "Knowledge is Power" published an article by the famous biologist A. A. Lyubimtsev "Frost patterns on glass." In it, the author draws the reader's attention tostriking similarity of ice patterns with plant structures. As an experiment, he photographed a pattern on glass and showed the photo to a botanist he knew. And without slowing down, he recognized the petrified footprint of a thistle in the picture. From the point of view of chemistry, these patterns arise due to the gas-phase crystallization of water vapor. However, something similar occurs in the production of pyrolytic graphite by pyrolysis of methane diluted with hydrogen. Thus, it was found that dendritic forms are formed away from this flow, which are very similar to plant remains. This is explained by the fact that there are general laws that govern the formation of forms in inorganic matter and wildlife.
For a long time, geologists have dated each geologic period based on traces of plant and animal forms found in coal deposits. And just a few years ago, there were statements by some scientists that this method was wrong and that all the fossils found were nothing more than a by-product of the formation of the earth's layers. There is no doubt that everything cannot be measured in the same way, but it is necessary to approach dating issues more carefully.
Was there a global glaciation?
Let's consider one more categorical statement of scientists, and not only geologists. All of us, starting from school, were taught about the global glaciation that covered our planet, as a result of which many animal species became extinct: mammoths, woolly rhinos and many others. And the modern younger generation is brought up on the quadrology "Ice Age". Scientists unanimously saythat geology is an exact science that does not allow theories, but uses only verified facts. However, this is not the case. Here, as in many areas of science (history, archeology, and others), one can observe the rigidity of theories and the steadfastness of authorities. For example, since the end of the nineteenth century, there has been heated debate on the sidelines of science about whether there was a glaciation or not. In the middle of the twentieth century, the famous geologist I. G. Pidoplichko published a four-volume work “On the Ice Age”. In this work, the author gradually proves the inconsistency of the version of global glaciation. He relies not on the works of other scientists, but on the geological excavations he personally carried out (moreover, he carried out some of them, being a Red Army soldier, participating in battles against the German invaders) throughout the territory of the Soviet Union and Western Europe. He proves that the glacier could not cover the entire continent, but was only local in nature, and that it did not cause the extinction of many animal species, but completely different factors - these are catastrophic events that led to the shift of the poles ("Sensational history of the Earth", A. Sklyarov); and economic activity of the person himself.
Mysticism, or Why Scientists Don't Notice the Obvious
Despite the irrefutable evidence provided by Pidoplichko, scientists are in no hurry to abandon the accepted version of glaciation. And then even more interesting. The author's works were published in the early 50s, however, with the death of Stalin, all copies of the four-volume edition were withdrawn from the libraries and universities of the country,were preserved only in the storerooms of libraries, and it is not easy to get them from there. In Soviet times, everyone who wanted to borrow this book from the library was registered with the special services. And even today there are certain problems in obtaining this printed edition. However, thanks to the Internet, anyone can get acquainted with the works of the author, who analyzes in detail the periods of the geological history of the planet, explains the origin of certain traces.
Geology is an exact science?
It is believed that geology is an exclusively experimental science, which draws conclusions only from what it sees. If the case is doubtful, then she does not state anything, expresses an opinion that allows for discussion, and postpones the final decision until unambiguous observations are obtained. However, as practice shows, the exact sciences are also wrong (for example, physics or mathematics). Nevertheless, mistakes are not a disaster if they are accepted and corrected in time. Often they are not global in nature, but have local significance, you just need to have the courage to accept the obvious, draw the right conclusions and move on towards new discoveries. Modern scientists show a radically opposite behavior, because most of the luminaries of science at one time received titles, awards and recognition for their work, and today they do not want to part with them at all. And such behavior is noticed not only in geology, but also in other fields of activity. Only strong people are not afraid to admit their mistakes, they rejoice at the opportunity to develop further, becausefinding a bug is not a disaster, but rather a new opportunity.
