The main stages of the geological history of the earth's crust. Fold belts and mountains

The period of the folding phase is the period of the most intense manifestation of internal forces in the geosyncline. At the same time, all other forms of manifestation of endogenous processes are activated: magmatic activity, earthquakes, etc.

As a result of the manifestation of folding phases, the structure of this section of the earth's crust changes dramatically. The area where folding occurs usually experiences uplift; if there was a sea here, then it recedes and land is formed, on which denudation processes begin to act. The locks of newly formed folds are usually cut off by denudation. During subsequent subsidence, marine sediments are deposited in this place on the eroded surface of folded layers. Consequently, the layers, folded into folds, are in contact with the newly deposited horizontal layers at a certain angle. This arrangement of rocks is called angular unconformity.

Baikal. It is divided into two phases: early (in the middle of R) and more common late ( boundary R-V). The structures of this era are very similar to the ancient platforms. The only difference is that the lower tier is one billion years younger (it includes Riphean deposits). Typical areas for the development of geosynclinal formations formed as a result of Baikal folding (Baikalids) are the folded systems of the Yenisei Ridge and the Baikal Mountain Region. Orogenic formations in these areas are of different ages (earlier on the Yenisei Ridge) and poorly differentiated. The specific features of the areas of Baikal folding in their tectonotype are the duration of formation, which corresponds to almost the entire Late Proterozoic, the predominantly sedimentary composition of thick accumulations of the shallow sea, the oppression of eugeosynclinal zones, and the limited granite formation, which is inferior in scale to a similar process in the era of the Caledonian folding. The Baikalides form the ancient cores of many Paleozoic folded systems: the Urals, Taimyr, Central Kazakhstan, the Northern Tien Shan, significant expanses of the basement of the West Siberian Plate, etc.

Salair. It also appeared in the form of two phases: the more common early (Є1-2) and late (O2).

Caledonian. Completed by the end of S. Divided into several phases. Distributed very widely. The Caledonian tectonomagmatic epoch was characterized not only by an increase in magmatism, but also led to a rise above sea level and the unification of the northern continents into a new supercontinent similar to southern Gondwana - Laurasia. The latter was separated from Gondwana by the large ocean Tethys [epoch of regression]. As a result of tectonic and magmatic activity, convergence and collision of continents in the Caledonian era, the highest and longest mountain-folded structures were formed. In the western hemisphere, these are the Appalachians, and in Central Asia - the mountain ranges of Central Kazakhstan, Altai, the Western and Eastern Sayan Mountains, the mountains of Mongolia, as well as the now flattened and destroyed mountain structures of Eastern Australia, the islands of Tasmania and Antarctica.

Hercynskaya. Completed by the end of the Paleozoic. Located between Gondwana and Laurussia, the Tethys Ocean ceased to exist. Then these giant continents united and one continent arose on the planet, which. There was also one ocean on the planet at that time. It was the giant ancient Pacific or Pantalas. The convergence and collision of lithospheric plates and blocks of the earth's crust led to the emergence of large mountain structures, which, after the name of the epoch, are called Hercynian mountain structures. These are Tibet, Hindu Kush, Karakoram, Tien Shan, Gorny and Rudny Altai, Kunlun, Urals, mountain systems of Central and Northern Europe, South and North America (Appalachians, Cordilleras), northwest Africa and Eastern Australia. As a result of the consolidation of stable areas that make up the lithospheric plates, epihercynian plates or young platforms arose. These include part of the West European platform, the Scythian, Turan and West Siberian plates, etc.

Mesozoic. Completed by the end of the Paleozoic. The upper tier is represented by blocky Cenozoic formations.

Alpine. Ended in the Paleogene. One of the areas of typical manifestation of Alpine folding is the Alps, in Europe - the Pyrenees, the Andalusian Mountains, the Apennines, the Carpathians, the Dinaric Mountains, the Balkans; in North Africa, the Atlas Mountains; in Asia - the Caucasus, the Pontic Mountains and the Taurus, the Turkmen-Khorasan Mountains, the Elburz and Zagros, the Suleiman Mountains, the Himalayas, the folded chains of Burma, Indonesia, Kamchatka, the Japanese and Philippine Islands; in North America - the folded ridges of the Pacific coast of Alaska and California; in South America - the Andes; archipelagos framing Australia from the east, incl. islands New Guinea and New Zealand. Alpine folding manifested itself not only within geosynclinal regions in the form of epigeosynclinal folded structures, but in some places also affected neighboring platforms - the Jura Mountains and part of the Iberian Peninsula (Iberian chains) in Western Europe, the southern part of the Atlas Mountains in North Africa, the Tajik depression and the southwestern spurs of the Hissar Range in Central Asia, the Eastern Rocky Mountains in North America, the Patagonian Andes in South America, the Antarctic Peninsula in Antarctica, etc.

Speaking of subduction processes, it should be said about the fate of sediments that overlap the oceanic lithosphere. The edge of the plate, under which the ocean subducts, cuts the sediments accumulated on it, like a bulldozer's knife, deforms these sediments and grows them to the continental plate in the form accretionary wedge. At the same time, some part of the sedimentary deposits sinks together with the plate into the depths of the mantle.

Also to be mentioned about a collision or collision, two continental plates, which, due to the relative lightness of the material that composes them, cannot sink under each other, but collide, forming a mountain-fold belt with a very complex internal structure. So, for example, the Himalayan mountains arose when the Hindustan plate collided with the Asian plate 50 million years ago. This is how the Alpine mountain-fold belt was formed during the collision of the African-Arabian and Eurasian continental plates.

Tests for self-control

Set the correct sequence in the alternation of geological periods.

1. paleogene

2. Specify metamorphic rocks

gneiss, granite

dolomite, chalk

marble, gneiss

quartzite, pumice

3. What geological period does the time of 75 million years belong to?

paleogene

4. Select the states where the most destructive earthquakes can occur

Finland 2) Honduras 3) Japan 4) Kazakhstan

5. What platforms or plates formed in the Archean - Proterozoic time?

Turan

Scythian

Siberian

South Chinese

6. Indicate the feature common to the continental and oceanic crust:

there is a granite layer;

the average thickness is 30-40 km;

characteristic three-layer structure;

continuous under continents and oceans.

7. Select the mountains that are the most ancient:

2. Cordillera;

   Scandinavian;

8. The age of modern mountains coincides with the age of folds in areas of ... folding

Baikal

Hercynian

Mesozoic

Cenozoic

9. Seismic belts of the Earth are formed:

only at the boundaries of the collision of lithospheric plates

only at the boundaries of expansion and rupture of lithospheric plates

at the boundaries of collision and rupture of lithospheric plates

in areas with the highest speed of movement of lithospheric plates

10. The eruption of which volcano led to the death of the city of Pompeii?

Etna 2) Hekla

3) Vesuvius 4) Krakatoa

11. The distribution of platform and folded areas on Earth is the main content of ... maps

1) soil 2) physical

3) geological 4) tectonic

12. Minerals of predominantly igneous origin include

1) hard and brown coal 2) copper and tin ores

3) natural gas and oil 4) table salt and asbestos

13. The age of modern mountains coincides with the age of folds in the regions .... folding

1) Baikal 2) Hercynian 3) Mesozoic 4) Cenozoic

14. At present, the zones of rift faults in the earth's crust on land are most clearly expressed on the continents

Australia and Africa

Africa and Eurasia

Eurasia and South America

South America and North America

15. Mountain systems were formed in one folding ...

1) Ural and Cordillera 2) Cordillera and Andes

3) Andes and the Caucasus 4) Caucasus and the Urals

The entire geological history of the Earth (about 4.5 billion years) is contained in a tiny geochronological table compiled by scientists. During this time, the continents split and moved, and the oceans changed their location. Mountains formed on the surface of our planet, then they collapsed, and then new mountain systems arose in their place - even larger and even higher.

This article will focus on one of the earliest epochs of terrestrial folding - the Baikal one. How long did it last? What mountain systems arose at this time? And what are the mountains of the Baikal folding - high or low?

Ages of folding of the Earth

The entire history of mountain building on our planet is divided by scientists into conditional intervals, periods, and they called them folding. We did this primarily for convenience. Of course, there have never been any pauses in the process of the formation of the earth's surface.

In total, there are six such periods in the history of the planet. The oldest folding is Archean, and the most recent is Alpine, which continues to this day. The following lists all the geological folding of the Earth in chronological order:

• Archean (4.5-1.2 billion years ago).
• Baikal (1.2-0.5 billion years ago).
• Caledonian (500-400 million years ago).
• Hercynian (400-230 million years ago).
• Mesozoic (160-65 million years ago).
• Alpine (65 million years ago to the present day).

Geomorphological structures that were formed in a particular era of mountain building are called accordingly - Baikalids, Hercynides, Caledonides, etc.

Baikal folding: chronological framework and general features of the era

The era of terrestrial tectogenesis, covering the period from 650 to 550 million years of the geological history of the Earth (Riphean - Cambrian), is commonly called the Baikal folding. It began about 1.2 billion years ago and ended about 500 million years ago. The geological epoch was named after Lake Baikal, since it was at this time that the southern part of Siberia was formed. The term was first used by the Russian geologist Nikolai Shatsky in the 1930s.

In the Baikal folding, due to the activation of the processes of folding, volcanism and granitization in the earth's crust, a number of new geological structures were formed on the body of our planet. As a rule, such formations arose on the outskirts of ancient platforms.

Typical folding can be found on the territory of Russia. This, for example, is the Khamar-Daban ridge in Buryatia or the Timan ridge in the north of the country. How do they look externally? Will the mountains be high or low? Let's answer this question too.

What do Baikalids look like?

The Baikalids formed a very long time ago. Even by geological standards of time. Therefore, it is quite logical that most of them are now in a dilapidated state. For millions of years, these structures were subjected to active denudation: they were destroyed by wind, atmospheric precipitation, and temperature changes. Thus, the mountains of the Baikal folding will be low or medium in height.

Indeed, the absolute heights of the Baikalids rarely exceed 2000 meters above sea level. This can be easily verified by comparing the tectonic and physical maps of the Earth. On geological and tectonic maps, the mountains of the Baikal folding, as a rule, are marked in purple.

True, the ancient Baikalids in many places on the globe were partially regenerated (rejuvenated) by later Alpine tectonic movements. So, for example, it happened in the mountains of the Caucasus and Turkey.

Significant reserves of non-ferrous metals are most often associated with the geological structures of the Baikal folding. So, within their limits are the richest deposits of mercury, tin, zinc, copper and tin.

Mountains of the Baikal folding: examples

Geological formations of this age are found in different corners planets. They are in Russia and Kazakhstan, Iran and Turkey, India, France and Australia. The Baikalides are located on the shores of the Red Sea and partially cover the territory of Brazil.

It is important to note that the term "Baikal folding" is common only in the scientific literature of the post-Soviet space. In other countries of the world, this era is called differently. So, for example, in Europe, it corresponds in time to the Kadom and Assinta folding, in Australia - Luinskaya, in Brazil - the Brazilian of the same name.

Within Russia, the following geomorphological structures are considered the most famous Baikalids:

• Eastern Sayan.
• Khamar-Daban.
• Baikal ridge.
• Yenisei Ridge.
• Timan Ridge.
• Patom Highlands.

Mountains of the Baikal folding in Russia. Baikal Range

The name of this ridge is consonant with the name of the era of mountain building we are considering. Therefore, we will begin the characterization of the main Baikalids of Russia with it.

The Baikal Range borders the depression of the lake of the same name from the north-western side. It is located within the Irkutsk region and Buryatia. Total length The ridge is 300 kilometers.

In the north, the Akitkan Ridge visually continues the geological structure. The average heights of this Baikalidae range from 1800-2100 meters. The highest point of the ridge is the peak of Chersky (2588 m). The mountain is named after the geographer who made a huge contribution to the study of the nature of the Baikal region.

Eastern Sayan

The Eastern Sayan is the largest mountain system in Southern Siberia, stretching for almost a thousand kilometers. Perhaps the most powerful of the Baikalids of Russia. The highest point of the Eastern Sayan reaches 3491 meters (mountain Munku-Sardyk).

The Eastern Sayan is composed mainly of hard crystalline rocks - gneisses, quartzites, marble and amphibolites. Large deposits of gold, bauxite and graphite have been discovered in its bowels. The most picturesque are the eastern spurs of the mountain system, nicknamed by tourists the Tunkinsky Alps.

The most developed (orographically) is the central part of the Eastern Sayan. It consists of alpine massifs, which are characterized by vegetation and landscapes of the subalpine type. Kurums are widespread within the Eastern Sayan. These are huge stone placers, consisting of rough fragments of rocks of various sizes.

Byrranga mountains

Byrranga are another interesting mountains of the Baikal folding. They are located on the northern Taimyr Peninsula. The mountains are a series of individual ridges, rolling plains and plateaus, deeply cut by canyons and trough valleys. The total length of the mountain system is about 1100 kilometers.

“There is a kingdom of evil spirits, stone, ice and nothing else,” wrote the Nganasans, representatives of one of the indigenous peoples of Siberia, about these places. The Russian traveler Alexander Middendorf was the first to put on the map.

These mountains are very low. Although they look quite impressive, as they are located right on the ocean. The height of their maximum point is only 1146 meters. The relief of this mountain system is very diverse. Here you can see both steep and gentle slopes, flat and pointed peaks, as well as a huge variety of glacial forms.

Yenisei and Timan ridges

We will finish our acquaintance with the Baikalids of Russia with a description of two ridges - the Yenisei and the Timan. The first of them is located within and only in some places exceeds a thousand meters in height. The Yenisei Ridge is composed of ancient and very hard rocks - conglomerates, shales, traps and sandstones. The structure is rich in iron ores, bauxite and gold.

The Timan Ridge is located in the north of the country. It stretches from the shores of the Barents Sea and adjoins the Ural Mountains. The total length of the ridge is about 950 km. The ridge is weakly expressed in the relief. The most elevated is its central part, where highest point- Chetlas stone (only 471 m high). Like other structures of the Baikal folding, the Timan Ridge is rich in minerals (titanium, bauxite, agate, and others).

Tectonic movements, magmatism and sedimentation. During the early Paleozoic, the earth's crust experienced strong tectonic movements, called the Caledonian folding. These movements did not manifest themselves simultaneously in the geosynclinal belts and reached their maximum at the end of the Silurian period. The most widespread Caledonian folding manifested itself in the Atlantic belt, a large northern part of which turned into a folded area of ​​the Caledonides. The Caledonian orogeny was accompanied by the emplacement of various intrusions.

In the tectonic movements of the early Paleozoic, a certain regularity is observed: in the Cambrian and the beginning of the Ordovician, subsidence processes prevailed, and at the end of the Ordovician and in the Silurian, uplift processes prevailed. These processes in the first half of the Early Paleozoic caused intensive sedimentation in geosynclinal belts and on ancient platforms, and then led to the creation of Caledonian mountain ranges in a number of areas of geosynclinal belts and to a general regression of the sea from the territory of ancient platforms.

The main areas of sedimentation were geosynclinal belts, where very thick, many kilometers long volcanic-sedimentary, terrigenous and carbonate formations accumulated. Carbonate and terrigenous sediments were formed on the ancient platforms of the northern hemisphere. Vast areas of sedimentation were located on the Siberian and Chinese-Korean platforms, and on the East European and North American platforms, sedimentation occurred in limited areas. Gondwana was predominantly an area of ​​erosion, and marine sedimentation occurred in minor marginal areas.

Physical and geographical conditions

According to the theory of lithospheric plate tectonics, the position and outlines of the continents and oceans in the Paleozoic differed from the modern one. By the beginning of the era and throughout the Cambrian, the ancient platforms (South American, African, Arabian, Australian, Antarctic, Hindustan), rotated by 180 °, were united into a single supercontinent called Gondwana. This supercontinent was located mainly in the southern hemisphere, from the south pole to the equator, and covered a total area of ​​more than 100 million km². Gondwana contained a variety of high and low plains and mountain ranges. The sea periodically invaded only the marginal parts of the supercontinent. The remaining smaller continents were located mainly in the equatorial zone: North American, East European and Siberian.

There were also microcontinents:

Central European, Kazakhstan and others. In the marginal seas there were numerous islands bordered by low-lying coasts with a large number of lagoons and river deltas. Between Gondwana and other continents there was an ocean, in the central part of which there were mid-ocean ridges. There were two largest plates in the Cambrian: the entirely oceanic Proto-Kula and the predominantly continental Gondwana plate.

In the Ordovician, Gondwana, moving south, entered the region of the South Geographic Pole (now it is the northwestern part of Africa). The Proto-Farallon oceanic lithospheric plate (and probably the Proto-Pacific plate) was subducted under the northern margin of the Gondwana plate. The reduction of the Proto-Atlantic basin, located between the Baltic Shield, on the one hand, and the single Canadian-Grenland Shield, on the other hand, began, as well as the reduction of oceanic space. During the entire Ordovician, there is a reduction in oceanic spaces and the closure of the marginal seas between the continental fragments: Siberian, Proto-Kazakhstan and China. In the Paleozoic (up to the Silurian - the beginning of the Devonian), the Caledonian folding continued. Typical Caledonides have survived in the British Isles, Scandinavia, North and East Greenland, Central Kazakhstan and the North Tien Shan, Southeast China, Eastern Australia, the Cordillera, South America, the Northern Appalachians, the Middle Tien Shan and other areas. As a result, the relief of the earth's surface at the end of the Silurian period became elevated and contrasting, especially on the continents located in the northern hemisphere. In the early Devonian, the closing of the Proto-Atlantic basin and the formation of the Euro-American continent took place, as a result of the collision of the Pro-European continent with the Pro-North American one in the region of present-day Scandinavia and Western Greenland. In the Devonian, the displacement of Gondwana continues, as a result, the South Pole is in the southern region of modern Africa, and possibly present-day South America. During this period, the Tethys ocean depression formed between Gondwana and the continents along the equatorial zone, three entirely oceanic plates were formed: Kula, Farallon and Pacific (which sank under the Australo-Antarctic margin of Gondwana).

In the Middle Carboniferous, Gondwana and Euroamerica collided. The western edge of the current North American continent collided with the northeastern margin of the South American, and the northwestern edge of Africa - with the southern edge of present-day Central and Eastern Europe. As a result, a new supercontinent, Pangea, was formed. In the late Carboniferous - early Permian, the Euro-American continent collided with the Siberian continent, and the Siberian continent with the Kazakhstan continent. At the end of the Devonian, the grandiose era of the Hercynian folding began with the most intense manifestation during the formation of the mountain systems of the Alps in Europe, accompanied by intense magmatic activity. In places where the platforms collided, mountain systems arose (with a height of up to 2000-3000 m), some of them have existed to this day, for example, the Urals or the Appalachians. Outside Pangea was only the Chinese block. By the end of the Paleozoic in the Persmian period, Pangea stretched from the South Pole to the North. The geographic South Pole at that time was within the boundaries of present-day East Antarctica. The Siberian continent, which was part of Pangea, which was the northern outskirts, approached the North Geographic Pole, not reaching it by 10--15 ° in latitude. The North Pole was in the ocean throughout the Paleozoic. At the same time, a single oceanic basin was formed with the main Proto-Pacific Basin and the Tethys Ocean Basin, which is the same with it.

Minerals

Early Paleozoic deposits are relatively poor in minerals. In contrast to the Precambrian, the first industrial deposits of combustible minerals, phosphorites, and rock salts were formed in the early Paleozoic. There are deposits of metallic minerals, but their share in the world reserves and production of mineral raw materials is small.

Combustible minerals - oil. and combustible gas - are of little industrial importance, their deposits are known in Russia on the Siberian platform, in the USA, Canada and in northern Africa. Of much greater importance are the Estonian oil shale deposits of Ordovician age.

Deposits of metallic minerals are divided into two groups. The first group includes rich deposits of iron and manganese ores of sedimentary origin. Huge reserves of sedimentary iron ores are found in the east of North America (Appalachian Mountains, Newfoundland). The second group includes deposits associated with igneous rocks - iron, manganese, copper, chromium, nickel, platinum and gold (Altai-Sayan region, Ural, Scandinavian mountains).

Of the non-metallic minerals, rock salt deposits in the south of the Siberian Platform near Irkutsk, in the USA, in Pakistan are of industrial importance. Large deposits of phosphorites are concentrated in the USA and China. Rich deposits of phosphorites are known on the Karatau Range in Central Asia (Cambrian), in the Baltic States (Ordovician), in the Eastern Sayan and Kuznetsk Alatau. Asbestos and talc deposits associated with ultramafic intrusions are known in the Urals.

The history of the Earth is subdivided into pregeological and geological.

Pregeological history of the Earth. The history of the Earth experienced a long chemical evolution before it turned from clots of cosmic matter into a planet. The time when the planet Earth began to form as a result of accretion is separated from the present by no more than 4.6 billion years, and the time during which accretion of the gas-dust nebula substance took place, according to some researchers, was short and amounted to no more than 100 million years. In the history of the Earth, a period of 700 million years - from the beginning of accretion to the appearance of the first dated rocks–It is customary to refer to the pregeological stage of the development of the Earth. The Earth was illuminated by the weak rays of the Sun, the light from which in those distant times was twice as weak as today. The young Earth at that time was subjected to increased meteorite bombardment and was a cold, uncomfortable planet covered with a thin crust of basalts. The Earth did not yet have an atmosphere and a hydrosphere, but powerful impacts of meteorites not only heated the planet, but, throwing out a huge amount of gases, contributed to the emergence of the primary atmosphere, the condensation of gases gave rise to the hydrosphere. From time to time, the basalt crust broke up, and massifs of hardened mantle matter “floated up” and sank along the cracks. The relief of the earth's surface resembled the modern lunar one, covered with a thin layer of loose regolith. It is believed that about 4.2 billion years ago, the Earth experienced active tectonic processes, which received the name of the Greenland period in geology. The earth began to warm up rapidly. Convective processes - the mixing of the Earth's substances, the chemical-density differentiation of the material of the Earth's spheres - led to the formation of the primary lithosphere and the origin of the oceans and atmosphere. The resulting primary atmosphere consisted of carbon dioxide, sulfur dioxide, water vapor and other components erupted by numerous volcanoes from rift zones. The first metamorphic and sedimentary rocks appeared - a thin earth's crust arose. Since that time (3.8-4 billion years ago), the actual geological history of the Earth begins.

Geological history of the Earth. This is the longest stage in the development of the Earth. The main events that have taken place on Earth since that time and up to the present era are shown in Fig. 3.4.

In the geological history of the Earth, various events took place during the long period of its existence. Numerous geological processes emerged, including tectonic ones, which led to the formation of the modern structural appearance of platforms, oceans, mid-ocean ridges, rifts, belts, and numerous minerals. Epochs of unusually intense magmatic activity were replaced by long periods with a weak manifestation of volcanic and magmatic activity. Epochs of enhanced magmatism were characterized by a high degree tectonic activity, i.e. significant horizontal movements of the continental blocks of the earth's crust, the occurrence of folded deformations, faults, vertical movements of individual blocks, and during periods of relative calm, geological changes in the relief of the earth's surface turned out to be weak.

Data on the age of igneous rocks, obtained by various methods of radiogeochronology, make it possible to establish the existence of relatively short periods of magmatic and tectonic activity and long periods of relative rest. This, in turn, makes it possible to carry out a natural periodization of the history of the Earth according to geological events, according to the degree of magmatic and tectonic activity.

Summary data on the age of igneous rocks, in fact, are a kind of calendar of tectonic events in the history of the Earth. Tectonic restructuring of the face of the Earth is carried out periodically by stages and cycles, which are called tectogenesis. These stages have manifested themselves and are manifesting themselves in different territories of the Earth and have different intensity. Cycle tectonic- long periods in the development of the earth's crust, beginning with the formation of geosynclines and ending with the formation of folded structures over vast areas of the globe; distinguish the Caledonian, Hercynian, Alpine, and other tectonic cycles. There are many tectonic cycles in the history of the Earth (there is information about 20 cycles), each of which is characterized by a peculiar magmatic and tectonic activity and the composition of the rocks that have arisen, the most studied of which are: Archean (Belozerskaya and Sami folding), Early Proterozoic (Belomorskaya and Seletska folding ), Middle Proterozoic (Karelian folding), Early Riphean (Grenville folding), Late Proterozoic (Baikal folding), Early Paleozoic (Caledonian folding), Late Paleozoic (Hercynian folding), Mesozoic (Cimmerian folding), Cenozoic (Alpine folding), etc. Each cycle ended with a closure on a greater or lesser part of the mobile areas and the formation of mountain-folded structures in their place - Baikalid, Caledonod, Hercynide, Mesozoid, Alpid. They successively "attached" to the ancient platform areas of the earth's crust stabilized in the Precambrian, resulting in the growth of the continents.

Rice. 3.4. The most important events in the geological history of the Earth (according to Koronovsky N.V., Yasamanov N.A., 2003)

Considering the existing structures of the earth's crust, one should take into account the evolution of the geological process, expressed in the complication of the geological phenomena themselves and the results of the manifestation of tectonic stages. So, the first geosynclines at the beginning of the Archean had a very simple structure, and vertical and horizontal movements of the cooled masses did not differ in strong contrast. In the Middle Proterozoic, ancient platforms, geosynclines, and mobile belts acquired a more complex structure and a significant variety of rocks that compose them. In the early Proterozoic, ancient platforms take shape. The Late Proterozoic and Paleozoic are considered to be the time of build-up of ancient platforms due to folded areas that experienced orogenesis processes and the platform stage. Most areas of the Mesozoic folding and part of the earlier one, the Hercynian in the Cenozoic, were subjected to extra-geosynclinal (block) orogeny, without having time to become platforms.

Evolutionary stages in the history of the Earth are manifested in the form of epochs of folding and mountain building, i.e. orogeny. So, in each tectonic stage, two parts are distinguished: a long evolutionary development and short-term violent tectonic processes, accompanied by regional metamorphism, the intrusion of acidic composition (granites and granodiorites) and mountain building.

The final part of the evolutionary cycle in geology is called folding era, which is characterized by a directed development and transformation of the geosynclinal system (mobile belt) into an epigeosynclinal orogen and the transition of the geosynclinal region (system) into a platform stage of development, or into non-geosynclinal mountain structures.

Evolutionary stages are characterized by the following features:

– long-term subsidence of mobile (geosynclinal) areas and accumulation in them of thick strata of sedimentary and volcanic-sedimentary strata;

– leveling of the land relief (the processes of erosion and washout of rocks on the continent predominate);

– widespread subsidence of platform margins adjacent to geosynclinal areas, their flooding with waters of epicontinental seas;

- equalization of climatic conditions due to the spread of shallow and warm epicontinental seas and humidification of the climate of the continents;

- the emergence of favorable conditions for the life and settlement of fauna and flora.

As can be seen from the features of the stages of the Earth's development, they have in common a wide distribution of marine clastic deposits (terrigenous), carbonate, organogenic and chemogenic. The stages of the evolutionary development of the Earth in geology are called thalassocratic ( from the Greek"talassa" - the sea, "kratos" - strength), when the areas of the platforms actively caved in and were flooded by the sea, i.e. major transgressions developed. Transgression- a kind of process of the advance of the sea on land, caused by the sinking of the latter, the rise of the bottom, or an increase in the volume of water in the basin. Thalassocratic epochs are distinguished by active volcanism, a significant influx of carbon into the atmosphere and ocean waters, the accumulation of thick layers of carbonate and terrigenous marine sediments, as well as the formation and accumulation of coal in coastal zones, oil in warm epicontinental seas.

The epochs of folding and mountain building have the following characteristic features:

– widespread development of mountain-building movements in mobile (geosynclinal) areas, oscillatory movements on the continents (platforms);

– manifestation of powerful intrusive and effusive magmatism;

– uplift of the margins of platforms adjacent to epigeosynclinal areas, regression of epicontinental seas and complication of land relief;

- the predominance of the continental climate, the strengthening of zoning, the expansion of arid zones, the increase in deserts and the appearance of areas of continental glaciation;

- extinction of dominant groups organic world due to the deterioration of conditions for its development, the renewal of entire groups of animals and plants.

The epochs of folding and mountain building are characterized by theocratic conditions (literally - the dominance of land) with the development of continental deposits; very often in the sections there are red-colored formations (with layers of carbonate, gypsum and saline rocks). These rocks are distinguished by a variety of genesis: continental and transitional from continental to marine.

In the geological history of the Earth, a number of characteristic and major stages of its development are distinguished.

ancient geological stage – Archaean(4.0-2.6 billion years ago). At this time, the bombardment of the Earth by meteorites began to decline and fragments of the first continental crust began to form, which gradually increased, but continued to experience fragmentation. In the deep Archean, or in the Katarchean, at the turn of 3.5 billion years, an outer liquid and solid inner core is formed approximately the same size as at the present time, as evidenced by the presence at that time of a magnetic field similar to the modern one in its characteristics. About 2.6 billion years ago, separate large massifs of the continental crust “soldered” into a huge supercontinent called Pangea 0. This supercontinent was probably opposed by the Panthalassa superocean with oceanic-type crust, i.e. not having a granite-metamorphic layer characteristic of the continental crust. The subsequent geological history of the Earth consisted in the periodic splitting of the supercontinent, the formation of the oceans, their subsequent closure with the sinking of the oceanic crust under the lighter continental crust, the formation of a new supercontinent - the next Pangea - and its new fragmentation.

Researchers agree that in the Early Archean the Earth formed the main volume of the lithosphere (80% of its modern volume) and the whole variety of rocks: igneous, sedimentary, metamorphic, as well as the core of protoplatforms, geosynclines. Low mountain-folded structures, the first aulacogenes, rifts, troughs, and deep-water depressions appeared.

In the geological development of subsequent stages, the build-up of continents is traced due to the closure of geosynclines and their transition to the platform stage. There is a split of the ancient continental crust into plates, the formation of young oceans, horizontal displacements over considerable distances of individual plates before their collision and thrusting, and, as a result, an increase in the thickness of the lithosphere occurs.

Early Proterozoic stage(2.6-1.7 billion years) the beginning of the breakup into separate large continental masses of the huge supercontinent Pangea-0, which existed for about 300 million years. The ocean is already developing according to the theory of lithospheric plate tectonics - spreading, subduction processes, the formation of active and passive continental margins, volcanic arcs, marginal seas. This time is marked by the appearance of free oxygen in the atmosphere due to photosynthetic cyanobionts. Red-colored rocks containing oxide iron begin to form. Approximately at the turn of 2.4 billion years, the appearance of the first extensive glaciation in the history of the Earth, called the Huronian (named after Lake Huron in Canada, on the coast of which the most ancient glacial deposits- moraines). About 1.8 billion years ago, the closure of ocean basins led to the creation of another supercontinent - Pangea-1 (according to Khain V.E., 1997) or Monogea (according to Sorokhtin O.G., 1990). Organic life develops very weakly, but organisms appear in whose cells the nucleus has already been isolated.

Late Proterozoic,or Riphean-Vendian stage(1.7-0.57 billion years.). The supercontinent Pangea-1 existed for almost 1 billion years. At that time, deposits accumulated either in continental conditions or in shallow marine environments, as evidenced by the very slight distribution of rocks of the ophiolite formation, characteristic of the oceanic type of crust. Paleomagnetic data and geodynamic analysis date the start of the collapse of the Pangea-1 supercontinent - about 0.85 billion years ago, oceanic basins formed between the continental blocks, a number of which closed by the beginning of the Cambrian, thereby increasing the area of ​​the continents. During the breakup of the supercontinent Pangea-1, the oceanic crust subducts under the continental one, and active continental margins with powerful volcanism, marginal seas, and island arcs are formed. Along the edges of the oceans increasing in size, passive margins were formed with a thick layer of sedimentary rocks. Separate large blocks of continents were inherited to one degree or another in later Paleozoic times (for example, Antarctica, Australia, Hindustan, North America, Eastern Europe etc., as well as the Proto-Atlantic and Proto-Pacific Ocean) (Fig. 3.5). The second largest glaciation, the Laplander, took place in the Vendian. At the turn of the Vendian and Cambrian - about 575 Ma. back - the most important changes take place in the organic world - the skeletal fauna appears.

For Paleozoic stage(575-200 million years), the trend established during the breakup of the supercontinent Pangea-1 continued. At the beginning of the Cambrian, depressions of the Atlantic Ocean (Iapetus Ocean), the Mediterranean belt (Tethys Ocean) and the Old Asian Ocean began to emerge in place of the Ural-Mongolian belt. But in the middle of the Paleozoic, a new association of continental blocks began, new mountain-building movements began (which began in the Carboniferous period and ended at the turn of the Paleozoic and Mesozoic, called the Hercynian movements), the Pro-Atlantic Ocean Iapetus and the Ancient Asian Ocean closed with the unification of the East Siberian and East European platforms through the folded structures of the Urals and the foundation of the future West Siberian plate. As a result, in the Late Paleozoic, another giant supercontinent Pangea-2 was formed, which was first identified by A. Wegener under the name Pangea.

Rice. 3.5. Reconstruction of the continents of the Late Proterozoic supercontinent Pangea-1 according to paleomagnetic data (according to Piper I.D. from the book Karlovich I.A., 2004)

One part of it - the North American and Eurasian plates - united into a supercontinent called Laurasia (sometimes Laurussia), the other - South American, African-Arabian, Antarctic, Australian and Hindustan - into Gondwana. The Tethys Ocean, which opened to the east, separated the Eurasian and African-Arabian plates. About 300 million years ago, in the high latitudes of Gondwana, the third major glaciation arose, which lasted until the end of the Carboniferous period. Then came the period global warming leading to the complete disappearance of the ice sheet.

In the Permian period, the Hercynian stage of development ends - the time of active mountain building, volcanism, during which large mountain ranges and massifs arose - Ural mountains, Tien Shan, Alay, etc., as well as more stable areas - the Scythian, Turan and West Siberian plates (the so-called epihercynian platforms).

An important event at the beginning of the Paleozoic era was the increase in the relative oxygen content in the atmosphere, which reached about 30% of the modern one, and the rapid development of life. Already at the beginning of the Cambrian period, all types of invertebrates and chordates existed and, as noted above, a skeletal fauna arose; 420 million years ago, fish appeared, after another 20 million years, plants came to land. The flowering of terrestrial biota is associated with the Carboniferous period. Tree forms - lycopsform and horsetail - reached 30-35 meters in height. A huge biomass of dead plants accumulated and eventually turned into coal deposits. At the end of the Paleozoic, parareptiles (cotilosaurs) and reptiles took the leading place in the animal kingdom. In the Permian period (about 250 million years ago), gymnosperms appeared. However, at the end of the Paleozoic there was a mass extinction of the biota.

For mesozoic stage(250-70 million years) significant changes took place in the geological history of the Earth. Tectonic processes covered platforms and folded belts. Particularly strong tectonic movements were manifested in the territory of the Pacific, Mediterranean and partially Ural-Mongolian belts. The Mesozoic era of mountain building is called cimmerian, and the structures created by it - Cimmerides or mesozoids. Folding processes were most intense at the end of the Triassic (Old Cimmerian folding phase) and at the end of the Jurassic (New Cimmerian phase). Magmatic intrusions are confined to this time. Folded structures arose in the Verkhoyansk-Chukotka and Cordillera regions. These sites developed into young platforms and merged with the Precambrian platforms. The structures of Tibet, Indochina, Indonesia were formed, the structure of the Alps, the Caucasus, etc. became more complex. Almost all platforms of the Pangea-2 supercontinent at the beginning of the Mesozoic era experienced a continental mode of development. From the Jurassic they began to sink, and the Cretaceous saw the greatest sea transgression in the northern hemisphere. The Mesozoic era determined the split of Gondwana and the formation of new oceans - the Indian and Atlantic. Strong trap volcanism took place in the places where the earth's crust was split - an outpouring of basalt lava that engulfed the Siberian platform in the Triassic, South America and South Africa, and in the Cretaceous - and India. The traps are of considerable thickness (up to 2.5 km). For example, on the territory of the Siberian platform, traps are distributed over an area of ​​more than 500 thousand km2.

On the territory of the Alpine-Himalayan and Pacific fold belts, tectonic movements actively manifested themselves, which caused different paleogeographic settings. On the ancient and young platforms in the Triassic, rocks of the red-colored continental formation accumulated, and in the Cretaceous, formations of carbonate rocks were formed, and thick coal strata accumulated in the troughs.

In the Triassic period, the formation of the Northern Ocean began, which at that time was not yet covered with ice, since the average annual temperature on Earth in the Mesozoic exceeded 20 ° C and there were no ice caps at the poles.

After the Paleozoic large-scale extinctions, the Mesozoic is characterized by the rapid evolution of new forms of flora and fauna. Mesozoic reptiles were the largest in the history of the Earth. Among the plant world, gymnosperms prevailed, later flowering plants appeared, and the dominant role passed to angiosperms. At the end of the Mesozoic, the "great Mesozoic extinction" occurred, when about 20% of families and more than 45% of different genera disappeared. Belemnites and ammonites, planktonic foraminifers, and dinosaurs have completely disappeared.

Cenozoic stage of the Earth's development (70 million years - up to the present). In the Cenozoic era, both vertical and horizontal movements were very intensive on the continents and in oceanic plates. The tectonic epoch that manifested itself in the Cenozoic era is called Alpine. It was most active at the end of the Neogene. Alpine tectogenesis covered almost the entire face of the Earth, but most strongly within the Mediterranean and Pacific mobile belts. Alpine tectonic movements differ from the Hercynian, Caledonian and Baikal ones by a significant amplitude of uplifts of both individual mountain systems and continents and subsidence of intermountain and oceanic depressions, the splitting of continents and oceanic plates and their horizontal movements.

At the end of the Neogene, the modern appearance of continents and oceans was formed on Earth. At the beginning of the Cenozoic era, rifting intensified on the continents and in the oceans, and the process of plate movement also intensified significantly. By this time, the separation of Australia from Antarctica. The completion of the formation of the northern part of the Atlantic Ocean falls on the Paleogene, the southern and central parts of which were fully opened in the Cretaceous. At the end of the Eocene, the Atlantic Ocean was almost within its present boundaries. The further development of the Mediterranean and Pacific belts is associated with the movement of lithospheric plates in the Cenozoic. Thus, the active movement of the African and Arabian plates to the north led to their collision with the Eurasian plate, which led to the almost complete closure of the Tethys Ocean, the remains of which were preserved within the boundaries of the modern Mediterranean Sea.

Paleomagnetic analysis of rocks on the continents and data from magnetometric measurements of the bottom of the seas and oceans made it possible to establish the course of changes in the position of the magnetic poles from the Early Paleozoic to the Cenozoic inclusive and trace the path of movement of the continents. It turned out that the position of the magnetic poles has an inversion character. In the early Paleozoic, the magnetic poles occupied places in the central part of the Gondwana mainland (the region of the modern Indian Ocean - the south pole) and in the vicinity of the northern coast of Antarctica (the Ross Sea - the north pole). The main number of continents at that time was grouped in the southern hemisphere closer to the equator. A completely different picture with magnetic poles and continents developed in the Cenozoic. So, the south magnetic pole began to be located northwest of Antarctica, and the north - northeast of Greenland. The continents are located mainly in the northern hemisphere and thus "liberated" the southern hemisphere for the ocean.

In the Cenozoic era, the spreading of the ocean floor, inherited from the Mesozoic and Paleozoic eras, continued. Some of the lithospheric plates were absorbed in subduction zones. For example, in the northeast of Eurasia in the Anthropogen (according to Sorokhtin I.G., Ushakov S.A., 2002), the continental and part of the oceanic plates with a total area of ​​about 120 thousand km2 subsided. The presence of mid-ocean ridges and banded magnetic anomalies, discovered by geophysicists in all oceans, testifies to seafloor spreading as the leading mechanism for the movement of oceanic plates.

In the Cenozoic era, the Farallon Plate, located on the East Pacific Rise, was divided into two plates - Nasca and Cocos. At the beginning of the Neogene period, the marginal seas and island arcs along the western periphery of the Pacific Ocean acquired an approximately modern appearance. In the Neogene, volcanism intensified on the island arcs, which continues to operate at the present time. For example, more than 30 volcanoes erupt in Kamchatka.

During the Cenozoic era, the outlines of the continents in the northern hemisphere changed in such a way that the isolation of the Arctic basin increased. The inflow of warm Pacific and Atlantic waters into it has decreased, and the removal of ice has decreased.

During the second half of the Cenozoic era (Neogene and Quaternary periods), the following occurred: 1) an increase in the area of ​​the continents and, accordingly, a decrease in the area of ​​the ocean; 2) an increase in the height of the continents and the depths of the oceans; 3) cooling of the earth's surface; 4) a change in the composition of the organic world, and an increase in its differentiation.

As a result of Alpine tectogenesis, Alpine folded structures arose: the Alps, the Balkans, the Carpathians, the Crimea, the Caucasus, the Pamirs, the Himalayas, the Koryak and Kamchatka ranges, the Cordilleras and the Andes. The development of mountain ranges in a number of places continues at the present time. This is evidenced by the uplift of mountain ranges, the high seismicity of the territories of the Mediterranean and Pacific mobile belts, active volcanism, as well as the ongoing process of lowering intermountain depressions (for example, the Kura in the Caucasus, Ferghana and Afghan-Tajik in Central Asia).

For the mountains of Alpine tectogenesis, a distinctive feature is the manifestation of horizontal displacements of young formations in the form of overthrusts, covers, ridges up to one-sided overturned occurrence towards rigid plates. For example, in the Alps, horizontal movements of sedimentary formations reach tens of kilometers in the Neogene (section along the Siplon tunnel). The mechanism of formation of fold systems, divergent overturning of folds in the Caucasus, in the Carpathians, etc., is explained by the compression of geosynclinal systems due to the movement of lithospheric plates. An example of the compression of sections of the earth's crust, which manifested itself in the Mesozoic, and especially in the Cenozoic era, is the Himalayas with the crowding of ridges and the formation of a powerful lithosphere due to the collision of the Himalayas and the Tien Shan, or the pressure of the Arabian and Hindustan plates from the south. Moreover, the movement is established not only for entire plates, but also for individual ridges. Thus, instrumental observations of the ridges of Peter I and the Gissar range showed that the first is moving towards the spurs of the Hissar range at a speed of 14-16 mm per year. If such horizontal movements continue, then in the near geological future intermountain plains and depressions in Uzbekistan, Tajikistan, Kyrgyzstan will disappear, and they will turn into mountain country similar to Nepal.

Alpine structures were compressed in many places, and the oceanic crust turned out to be pushed over the continental one (for example, in the region of Oman in the east of the Arabian Peninsula). Part of the young platforms in modern times experienced a sharp rejuvenation of the relief by blocky shifts (Tien Shan, Altai, Sayans, Urals).

Glaciation in the Quaternary period covered 60% of the territory of North America, 25% of Eurasia and about 100% of Antarctica, including the glaciers of the shelf belt. It is customary to distinguish between terrestrial, underground (permafrost) and mountain glaciation. Terrestrial glaciation manifested itself in the subarctic, in the temperate zone and in the mountains. These belts were characterized by an abundance of precipitation and the predominance of negative temperatures.

In North America, there are traces of six glaciations - Nebraska, Kansas, Iowa, Illinois, Early Wisconsin and Late Wisconsin. The center of the North American glaciation was located in the northern part of the Cordilleras, the Laurentian Peninsula (Labrador and Kivantin) and Greenland.

The center of European glaciation covered a vast territory: Scandinavia, the mountains of Ireland, Scotland, Great Britain, New Earth and the Polar Urals. In the European part of Eurasia, at least six times, and in Western Siberia five times, glaciation occurred (Table 3.3).

Table 3.3

Glacial and interglacial epochs of Russia (according to Karlovich I.A., 2004)

The average duration of glacial epochs was 50-70 thousand years. The largest glaciation is considered to be the Dnieper (Samarov) glaciation. The length of the Dnieper glacier in the south direction reached 2200 km, in the east - 1500 km and in the north - 600 km. And the smallest glaciation is considered to be the Late Valdai (Sartan) glaciation. About 12 thousand years ago, the last glacier left the territory of Eurasia, and in Canada it melted about 3 thousand years ago and survived in Greenland and the Arctic.

It is known that there are many reasons for glaciation, but the main ones are cosmic and geological. After the general regression of the seas and the uplift of the land took place in the Oligocene, the climate on Earth became drier. At this time, there was a rise of land around the Arctic Ocean. Warm sea currents, as well as air currents, changed their direction. An almost similar situation has developed in the regions adjacent to Antarctica. It is assumed that in the Oligocene the height of the Scandinavian mountains was somewhat higher than the modern one. All this led to the onset of cooling here. The Pleistocene ice age covered the northern and southern hemispheres in some places (Scandinavian and Antarctic glaciation). Glaciations in the northern hemisphere influenced the composition and distribution of terrestrial groups of mammals, and especially ancient man.

In the Cenozoic era, the place of organisms that disappeared in the Mesozoic era is occupied by completely different forms of flora and fauna. The vegetation is dominated by angiosperms. Among marine invertebrates, gastropods and bivalve mollusks, six-ray corals and echinoderms, bony fish are moving forward to the leading positions. Of the reptiles, only snakes, turtles and crocodiles survived the catastrophe in the depths of the seas and oceans. Mammals spread rapidly - not only on land, but also in the seas.

The next cooling at the turn of the Neogene and the Quaternary period contributed to the disappearance of some forms of heat-loving and the emergence of new animals adapted to the harsh climate - wolves, reindeer, bears, bison, etc.

At the beginning of the Quaternary animal world The land gradually acquired a modern look. by the most important event the Quaternary period was the appearance of man. This was preceded by a long evolution of primates (Table 3.4) from Dryopithecus (about 20 million years ago) to Homo sapiens (about 100 thousand years ago).

Table 3.4

The evolution of primates from Dryopithecus to modern man

Cro-Magnons by appearance little different from modern people, knew how to make spears, arrows with stone tips, stone knives, axes, lived in caves. The time interval from the appearance of the Pithecanthropus to the Cro-Magnons is called the Paleolithic (Ancient Stone Age). It is replaced by the Mesolithic and Neolithic (Middle and Late Stone Age). After him comes the age of metals.

The Quaternary period is the time of the formation and development of human society, the time of the strongest climatic events: the onset and periodic change of glacial epochs by interglacials.