EntranceGeological eras in chronological order. Geological age of the earth
In the beginning there was nothing. In the endless space there was only a giant cloud of dust and gases. It can be assumed that from time to time spaceships carrying representatives of the universal mind rushed through this substance at great speed. The humanoids looked boredly out the windows and did not even remotely realize that in a few billion years intelligence and life would arise in these places.
The gas and dust cloud transformed over time into the Solar System. And after the star appeared, the planets appeared. One of them was our native Earth. This happened 4.5 billion years ago. It is from those distant times that the age of the blue planet is counted, thanks to which we exist in this world.
Stages of Earth's development
The entire history of the Earth is divided into two huge stages.. The first stage is characterized by the absence of complex living organisms. There were only single-celled bacteria that settled on our planet about 3.5 billion years ago. The second stage began approximately 540 million years ago. This is the time when living multicellular organisms spread across the Earth. This refers to both plants and animals. Moreover, both seas and land became their habitat. The second period continues to this day, and its crown is man.
Such huge time stages are called eons. Each eon has its own eonothema. The latter represents a certain stage of the geological development of the planet, which is radically different from other stages in the lithosphere, hydrosphere, atmosphere, and biosphere. That is, each eonoteme is strictly specific and not similar to others.
There are 4 eons in total. Each of them, in turn, is divided into eras of the Earth, and those are divided into periods. From this it is clear that there is a strict gradation of large time intervals, and the geological development of the planet is taken as the basis.
Katarhey
The oldest eon is called Katarchean. It began 4.6 billion years ago and ended 4 billion years ago. Thus, its duration was 600 million years. Time is very ancient, so it was not divided into eras or periods. During the times of the Catarchaeus there was neither earth's crust, no core. The planet was a cold cosmic body. The temperature in its depths corresponded to the melting point of the substance. From above, the surface was covered with regolith, like the lunar surface in our time. The relief was almost flat due to constant powerful earthquakes. Naturally, there was no atmosphere or oxygen.
Archaea
The second eon is called Archean. It began 4 billion years ago and ended 2.5 billion years ago. Thus, it lasted 1.5 billion years. It is divided into 4 eras: Eoarchean, Paleoarchean, Mesoarchean and Neoarchean.
Eoarchaean(4-3.6 billion years) lasted 400 million years. This is the period of formation of the earth's crust. A huge number of meteorites fell on the planet. This is the so-called Late Heavy Bombardment. It was at that time that the formation of the hydrosphere began. Water appeared on Earth. Comets could have brought it in large quantities. But the oceans were still far away. There were separate reservoirs, and the temperature in them reached 90° Celsius. The atmosphere was characterized by a high content of carbon dioxide and a low content of nitrogen. There was no oxygen. At the end of the era, the first supercontinent of Vaalbara began to form.
Paleoarchaean(3.6-3.2 billion years) lasted 400 million years. During this era, the formation of the solid core of the Earth was completed. A strong magnetic field appeared. His tension was half the current one. Consequently, the surface of the planet received protection from the solar wind. This period also saw primitive forms of life in the form of bacteria. Their remains, which are 3.46 billion years old, were discovered in Australia. Accordingly, the oxygen content in the atmosphere began to increase, due to the activity of living organisms. The formation of Vaalbar continued.
Mesoarchean(3.2-2.8 billion years) lasted 400 million years. The most remarkable thing about it was the existence of cyanobacteria. They are capable of photosynthesis and produce oxygen. The formation of the supercontinent has completed. By the end of the era it had split. There was also a huge asteroid impact. The crater from it still exists in Greenland.
Neoarchaean(2.8-2.5 billion years) lasted 300 million years. This is the time of formation of the real earth's crust - tectogenesis. Bacteria continued to develop. Traces of their life were found in stromatolites, whose age is estimated at 2.7 billion years. These lime deposits were formed by huge colonies of bacteria. They were found in Australia and South Africa. Photosynthesis continued to improve.
With the end of the Archean era, the Earth's era continued in the Proterozoic eon. This is a period of 2.5 billion years - 540 million years ago. It is the longest of all the eons on the planet.
Proterozoic
The Proterozoic is divided into 3 eras. The first one is called Paleoproterozoic(2.5-1.6 billion years). It lasted 900 million years. This huge time interval is divided into 4 periods: siderian (2.5-2.3 billion years), rhyasium (2.3-2.05 billion years), orosirium (2.05-1.8 billion years) , stateria (1.8-1.6 billion years).
Siderius notable in the first place oxygen catastrophe. It happened 2.4 billion years ago. Characterized by a dramatic change in the Earth's atmosphere. Free oxygen appeared in it in huge quantities. Before that, the atmosphere was dominated carbon dioxide, hydrogen sulfide, methane and ammonia. But as a result of photosynthesis and the extinction of volcanic activity at the bottom of the oceans, oxygen filled the entire atmosphere.
Oxygen photosynthesis is characteristic of cyanobacteria, which proliferated on Earth 2.7 billion years ago. Before this, archaebacteria dominated. They did not produce oxygen during photosynthesis. In addition, oxygen was initially consumed in the oxidation of rocks. It accumulated in large quantities only in biocenoses or bacterial mats.
Eventually, a moment came when the surface of the planet became oxidized. And the cyanobacteria continued to release oxygen. And it began to accumulate in the atmosphere. The process accelerated due to the fact that the oceans also stopped absorbing this gas.
As a result, anaerobic organisms died, and they were replaced by aerobic ones, that is, those in which energy synthesis was carried out through free molecular oxygen. The planet was shrouded in the ozone layer and the greenhouse effect decreased. Accordingly, the boundaries of the biosphere expanded, and sedimentary and metamorphic rocks turned out to be completely oxidized.
All these metamorphoses led to Huronian glaciation, which lasted 300 million years. It began in Sideria, and ended at the end of Rhiasia 2 billion years ago. The next period of orosiria is notable for its intense mountain building processes. At this time, 2 huge asteroids fell on the planet. The crater from one is called Vredefort and is located in South Africa. Its diameter reaches 300 km. Second crater Sudbury located in Canada. Its diameter is 250 km.
Last staterian period notable for the formation of the supercontinent Columbia. It includes almost all the continental blocks of the planet. There was a supercontinent 1.8-1.5 billion years ago. At the same time, cells were formed that contained nuclei. That is, eukaryotic cells. This was a very important stage of evolution.
The second era of the Proterozoic is called Mesoproterozoic(1.6-1 billion years). Its duration was 600 million years. It is divided into 3 periods: potassium (1.6-1.4 billion years), exatium (1.4-1.2 billion years), sthenia (1.2-1 billion years).
During the time of Kalimium, the supercontinent Colombia broke up. And during the Exatian era, red multicellular algae appeared. This is indicated by a fossil find on the Canadian island of Somerset. Its age is 1.2 billion years. A new supercontinent, Rodinia, formed in Stenium. It arose 1.1 billion years ago and disintegrated 750 million years ago. Thus, by the end of the Mesoproterozoic there was 1 supercontinent and 1 ocean on Earth, called Mirovia.
The last era of the Proterozoic is called Neoproterozoic(1 billion-540 million years). It includes 3 periods: Thonian (1 billion-850 million years), Cryogenian (850-635 million years), Ediacaran (635-540 million years).
During the Thonian era, the supercontinent Rodinia began to disintegrate. This process ended in cryogeny, and the supercontinent Pannotia began to form from 8 separate pieces of land formed. Cryogeny is also characterized by complete glaciation of the planet (Snowball Earth). The ice reached the equator, and after it retreated, the process of evolution of multicellular organisms sharply accelerated. The last period of the Neoproterozoic Ediacaran is notable for the appearance of soft-bodied creatures. These multicellular animals are called Vendobionts. They were branching tubular structures. This ecosystem is considered the oldest.
Life on Earth originated in the ocean
Phanerozoic
Approximately 540 million years ago, the time of the 4th and last eon began - the Phanerozoic. There are 3 very important eras of the Earth. The first one is called Paleozoic(540-252 million years). It lasted 288 million years. Divided into 6 periods: Cambrian (540-480 million years), Ordovician (485-443 million years), Silurian (443-419 million years), Devonian (419-350 million years), Carboniferous (359-299 million years) and Permian (299-252 million years).
Cambrian considered to be the lifespan of trilobites. These are marine animals similar to crustaceans. Along with them, jellyfish, sponges and worms lived in the seas. Such an abundance of living beings is called Cambrian explosion. That is, there was nothing like this before and suddenly it suddenly appeared. Most likely, it was in the Cambrian that mineral skeletons began to emerge. Previously, the living world had soft bodies. Naturally, they were not preserved. Therefore, complex multicellular organisms of more ancient eras cannot be detected.
The Paleozoic is notable for the rapid expansion of organisms with hard skeletons. From vertebrates, fish, reptiles and amphibians appeared. The plant world was initially dominated by algae. During Silurian plants began to colonize the land. At first Devonian The swampy shores are overgrown with primitive flora. These were psilophytes and pteridophytes. Plants reproduced by spores carried by the wind. Plant shoots developed on tuberous or creeping rhizomes.
Plants began to colonize land during the Silurian period
Scorpions and spiders appeared. The dragonfly Meganeura was a real giant. Its wingspan reached 75 cm. Acanthodes are considered the oldest bony fish. They lived during the Silurian period. Their bodies were covered with dense diamond-shaped scales. IN carbon, which is also called the Carboniferous period, a wide variety of vegetation rapidly developed on the shores of lagoons and in countless swamps. It was its remains that served as the basis for the formation of coal.
This time is also characterized by the beginning of the formation of the supercontinent Pangea. It was fully formed during the Permian period. And it broke up 200 million years ago into 2 continents. These are the northern continent of Laurasia and the southern continent of Gondwana. Subsequently, Laurasia split, and Eurasia and North America were formed. And from Gondwana arose South America, Africa, Australia and Antarctica.
On Permian there were frequent climate changes. Dry times alternated with wet ones. At this time, lush vegetation appeared on the banks. Typical plants were cordaites, calamites, tree and seed ferns. Mesosaur lizards appeared in the water. Their length reached 70 cm. But by the end of the Permian period, early reptiles died out and gave way to more developed vertebrates. Thus, in the Paleozoic, life firmly and densely settled on the blue planet.
The following eras of the Earth are of particular interest to scientists. 252 million years ago came Mesozoic. It lasted 186 million years and ended 66 million years ago. Consisted of 3 periods: Triassic (252-201 million years), Jurassic (201-145 million years), Cretaceous (145-66 million years).
The boundary between the Permian and Triassic periods is characterized by mass extinction of animals. 96% of marine species and 70% of terrestrial vertebrates died. The biosphere was dealt a very strong blow, and it took a very long time to recover. And it all ended with the appearance of dinosaurs, pterosaurs and ichthyosaurs. These sea and land animals were of enormous size.
But the main tectonic event of those years was the collapse of Pangea. A single supercontinent, as already mentioned, was divided into 2 continents, and then broke up into the continents that we know now. The Indian subcontinent also broke away. It subsequently connected with the Asian plate, but the collision was so violent that the Himalayas emerged.
This is what nature was like in the early Cretaceous period
The Mesozoic is notable for being considered the warmest period of the Phanerozoic eon.. This is the time of global warming. It began in the Triassic and ended at the end of the Cretaceous. For 180 million years, even in the Arctic there were no stable pack glaciers. Heat spread evenly across the planet. At the equator, the average annual temperature was 25-30° Celsius. The circumpolar regions were characterized by a moderately cool climate. In the first half of the Mesozoic, the climate was dry, while the second half was characterized by humid climate. It was at this time that the equatorial climate zone was formed.
In the animal world, mammals arose from the subclass of reptiles. This was due to the improvement of the nervous system and brain. The limbs moved from the sides under the body, and the reproductive organs became more advanced. They ensured the development of the embryo in the mother's body, followed by feeding it with milk. Hair appeared, blood circulation and metabolism improved. The first mammals appeared in the Triassic, but they could not compete with dinosaurs. Therefore, for more than 100 million years they occupied a dominant position in the ecosystem.
The last era is considered Cenozoic(beginning 66 million years ago). This is the current geological period. That is, we all live in the Cenozoic. It is divided into 3 periods: Paleogene (66-23 million years), Neogene (23-2.6 million years) and the modern Anthropocene or Quaternary period, which began 2.6 million years ago.
There are 2 main events observed in the Cenozoic. The mass extinction of dinosaurs 65 million years ago and the general cooling of the planet. The death of the animals is associated with the fall of a huge asteroid with a high content of iridium. The diameter of the cosmic body reached 10 km. As a result, a crater was formed Chicxulub with a diameter of 180 km. It is located on the Yucatan Peninsula in Central America.
Surface of the Earth 65 million years ago
After the fall, there was an explosion of enormous force. Dust rose into the atmosphere and blocked the planet from the sun's rays. The average temperature dropped by 15°. Dust hung in the air for a whole year, which led to a sharp cooling. And since the Earth was inhabited by large heat-loving animals, they became extinct. Only small representatives of the fauna remained. It was they who became the ancestors of the modern animal world. This theory is based on iridium. The age of its layer in geological deposits corresponds exactly to 65 million years.
During the Cenozoic, the continents diverged. Each of them formed its own unique flora and fauna. The diversity of marine, flying and terrestrial animals has increased significantly compared to the Paleozoic. They became much more advanced, and mammals took a dominant position on the planet. Higher angiosperms appeared in the plant world. This is the presence of a flower and an ovule. Cereal crops also appeared.
The most important thing in the last era is anthropogen or quaternary period, which began 2.6 million years ago. It consists of 2 eras: the Pleistocene (2.6 million years - 11.7 thousand years) and the Holocene (11.7 thousand years - our time). During the Pleistocene era Mammoths, cave lions and bears, marsupial lions, saber-toothed cats and many other species of animals that became extinct at the end of the era lived on Earth. 300 thousand years ago, man appeared on the blue planet. It is believed that the first Cro-Magnons chose the eastern regions of Africa. At the same time, Neanderthals lived on the Iberian Peninsula.
Notable for the Pleistocene and Ice Ages. For as long as 2 million years, very cold and warm periods of time alternated on Earth. Over the past 800 thousand years, there have been 8 ice ages with an average duration of 40 thousand years. During cold times, glaciers advanced on the continents, and retreated during interglacial periods. At the same time, the level of the World Ocean rose. About 12 thousand years ago, already in the Holocene, the next ice age ended. The climate became warm and humid. Thanks to this, humanity spread throughout the planet.
The Holocene is an interglacial. It has been going on for 12 thousand years. Over the past 7 thousand years, human civilization has developed. The world has changed in many ways. Flora and fauna have undergone significant transformations thanks to human activity. Nowadays, many animal species are on the verge of extinction. Man has long considered himself the ruler of the world, but the era of the Earth has not gone away. Time continues its steady course, and the blue planet conscientiously revolves around the Sun. In a word, life goes on, but the future will show what will happen next.
The article was written by Vitaly Shipunov
Studying the contents of the paragraph provides the opportunity to: study the history of the formation of the Earth and methods for determining the age of rocks; become familiar with the geochronological scale and its use in practical activities.
What is the Universe, the Solar theme? What are “gravitational forces”? There are many different hypotheses for the origin of the Earth. They are discussed in detail in the astronomy course. Currently, the most common hypothesis is O. Yu. gas-dust cloud. Particles
These clouds, revolving around the Sun, collided, “stuck together,” forming clumps that grew like a snowball. It is believed that age solar system(including the Earth) is about 5 billion years. As a result of the evolution of the Earth, the rocks that make up the earth's crust were formed.
The time and sequence of formation of rocks is called geological chronology. There are absolute and relative ages of rocks. The absolute age is calculated from the beginning of rock formation to the present. It dates back thousands, millions and even billions of years and is mainly determined by studying the decay of radioactive chemical elements. The age of the most ancient rocks studied on the globe reaches 3.8 billion years.
Relative age reflects the sequence of deposition of rock layers in a geological section. The main methods for determining the relative age of rocks are stratigraphic (from Latin stratum - layer and Greek grapho - describe) - the ratio of layers, sedimentary strata
"petrographic (from the Greek petros - stone, grapho - description) - the study of the composition of rocks; paleontological (from the Greek palaios - ancient, logas - study) - the study of the remains of ancient extinct organisms; spore-pollen analysis - based on the results of analysis of spores and pollen of ancient plants" isotopic - based on radioactive isotopes.
The branch of historical geology that studies the sequence of formation of the forge is called stratigraphy. When rocks are undisturbed, the upper layers are younger than the lower ones. The arrangement of geological layers as they form from older to younger is called a stratigraphic column or stratigraphic scale. If this scale is expressed in time units divided into eras, periods and epochs, then it is called the geological time scale or geochronological scale (see Appendices). (Think about what you think the names of geological eras reflect. Which era is the most recent?)
The geochronological scale can reflect the time of formation of mountain systems, minerals, the emergence of life or the disappearance of its individual forms.
The entire history of the Earth is usually divided into 2 stages: the Precambrian, or cryptozoic (planetary period), and the Phanerozoic (geological period).
If we take the age of the Earth to be 4.6 billion years, then the Cryptozoic lasted about 4 billion years, and the Phanerozoic lasted 570 million years.
The Precambrian (cryptozoic) is a period of time in the history of the evolution of the Earth, which is conventionally called its planetary stage.
The Precambrian is divided into two eras: Archean (ancient) and Proterozoic (early). The Archean is characterized by several epochs of folding, the formation of a shallow ocean with many volcanic islands, and the formation of an atmosphere with the presence of free oxygen. With the advent of the atmosphere and hydrosphere, the process of physical weathering and images began: ia of sedimentary deposits.
In the Archean, life arose in an aquatic environment, which was not interrupted on Earth throughout the subsequent history of its development.
The next era - the Proterozoic - is characterized by several eras of folding, the formation of crystalline rocks of the foundation of ancient platforms. During this period, the volume of water in the ocean increased, the composition of the atmosphere changed (oxygen content reached 0.01% of the modern level), and invertebrates developed. Precambrian rocks form the foundation and lower part of the ancient platform cover: platforms.
The Phanerozoic spans the Paleozoic, Mesozoic and Cenozoic eras of geological history.
The Paleozoic is divided into 6 periods. (What are these periods called?) In the Ordovician, water acquired a composition close to that of today. In the Ordovician and Silurian, the Caledonian folding appeared. The land rose, and extensive retreats of warm seas occurred. The oxygen content in the atmosphere reached 10% of the modern level, and the formation of the ozone layer occurred.
The Devonian, Carboniferous (Carboniferous) and Permian are characterized by another combination of procontinents. In the Paleozoic, plants and animals began to move onto land. Active transformation has begun environment living organisms through biological and biochemical processes. This promoted differentiation (diversity) natural complexes, increasing complexity of physical and geographical conditions and diversity of landscapes.
In the Carboniferous, thick layers of coal were formed, which determined the name of the period. The oxygen content in the atmosphere has approached current state. During the Permian period, a planetary cooling of the climate occurred, and glaciations formed in the Northern and Southern Hemispheres.
During the Mesozoic era, young mountains formed in areas of Mesozoic folding, the formation of modern oceans began, in which sediments accumulated, giant reptiles (dinosaurs) flourished, and then their extinction occurred.
The next era of the geological history of the Earth is the Cenozoic (Cenozoic). (Using a geochronological scale, determine the beginning and division of the era into periods.)
The last period of the Cenozoic era is called the Quaternary (or Anthropocene), which is divided into the Eopleistocene, Pleistocene and Holocene. (Remember from history how many years ago man appeared.)
The first segment of the Anthropocene is also called ice age. The total area of the continental glacier at that time reached 48 ml! km2, which is three times the area of Antarctica. In Europe, the glacier spread south to 49.5° N. sh., in North America - tgt; o7.5° N. w.
Glaciations consist of several stages, which alternated with interglacial eras.
The Czech scientist J. Augusta spoke very eloquently about the relationship and duration of different eras, periods and epochs in the general geological history of the Earth in his book “On the Paths of the Development of Life”: “... if the duration of the entire geological history of the Earth is conventionally taken to be the duration of one year. Then, on this scale, the Archean and Proterozoic will correspond almost entirely to the first three quarters of the year, that is, the time from the beginning of January to the last days of September; the formation of the earth's crust would have occurred in early spring, but without oceans and before the emergence of life. The emergence of life would have occurred around the beginning of May, and the first stage of invertebrate development during the Proterozoic period would have taken all summer until the beginning of autumn, until approximately half of September, when the Paleozoic would begin with the flowering of invertebrates, fish and amphibians. This period would have lasted approximately until the last days of November, when the Mesozoic - the era of giant reptiles - would have begun, which would have ended in the last week of December... On this scale, the Quaternary period would have taken only less than a day, and on this day man would have appeared approximately at 8 o'clock in the evening. The entire history of science and culture of mankind would fit into this scale in just a few last minutes of the year!.."
? 1. How is geological chronology used to determine the age of the Earth?
2. Make a free-form table reflecting the most important events that occurred on Earth in the Paleozoic, Mesozoic, and Cenozoic eras.
3*. Why did the emergence of plants and animals on land contribute to the differentiation of the geographical envelope?
1. Precambrian divisions.
The Archean-Proterozoic, or Cryptozoic, stage covers the history of the Earth over 4 billion years. It lasted almost 7 times longer than the Phanerozoic. During this time, all existing external shells were formed - the lithosphere, hydrosphere and atmosphere.
| Precambrian geochronological scale | |||
| Relative geochronology | |||
| Eras (groups) | Parts of eras (subgroups) | ||
| Proterozoic - PR | Late Proterozoic - PR3 | Vend-V | |
| Riphean –R | Late Riphean-R3 | ||
| Medium Riphean-R2 | |||
| early Riphean-R1 | |||
| Middle Proterozoic - PR2 | |||
| Early Proterozoic - PR1 | |||
| Archean - AR | late Archaean - AR2 | ||
| early Archaean (Catarchaean) - AR1 | |||
2. History of the development of the Earth in the Precambrian.
The Precambrian, covering the vast majority of the geological history of the Earth (over 80%), remains at the same time the least studied period of time. Due to the high degree of metamorphism of the Precambrian strata, the lack of fossil remains, weak exposure of Precambrian rocks, etc.
According to a number of scientists, First stage geological development of the Earth was still platformless and without geosynclinal. At this stage of development, the primary earth's crust had a basic composition and was formed due to basaltic outpourings from the upper mantle. At the same time, numerous dome-shaped uplifts up to 50-60 km in diameter were already appearing in the primary earth's crust, in which the first granitized sections of the earth's crust began to emerge. This entire stage of development is called the nuclear stage; it continued until the end of the Archean era.
The next stage in the tectonic development of the earth's crust begins at the end of the Archean, when deep linear troughs called protogeosynclines are formed on the nuclear earth's crust. They accumulated clastic material carried down from areas of ancient granitization and protruding parts of the primary basaltic crust.
Under the influence of the most ancient eras of tectogenesis - the Sami and the White Sea - at the end of the Archean - the beginning of the Proterozoic, the first platform formations were formed - protoplatforms, separated by geosynclinal troughs.
The youngest protogeosynclines ceased to exist at the beginning of the Middle Proterozoic. With their disappearance, the formation of a number of rock complexes and formations typical of this stage of development - leptites, migmatites, charnockites and jaspilites - ceased.
The next era of tectogenesis, the Karelian, appeared at the end of the Middle Proterozoic.
With the end of the Karelian folding, large platforms arose, between which geosynclinal troughs continued to develop; in which rocks of a new type accumulated (algal limestones and dolomites, carbonaceous and graphitic shales).
In the Northern Hemisphere, in the interval between the Karelian and Baikal epochs of tectogenesis, intense tectonic movements did not occur, unlike the Southern Hemisphere.
The Baikal era of tectogenesis appeared at the end of the Riphean - the beginning of the Cambrian period. Its structures form the Timan-Pechora region, the western, southwestern and southern framing of the Siberian Platform, which arose in the marginal zones of the Ural-Mongolian geosynclinal belt.
By the end of the Riphean Baikal tectogenesis, the formation of a number of geosynclinal troughs is noted - a manifestation of a new era of tectogenesis - the Caledonian, which arose, in particular, in the same Ural-Mongolian geosynclinal belt within the Sayan and Altai.
There is an idea that by the end of the Proterozoic era, all the southern ancient platforms - South American, African, Indian, Australian and East Antarctic - were “fused” into one vast continent, described as Gondwana. It also included the territories now occupied by the depressions of the Indian and southern parts. Atlantic Oceans.
3.Organic world and minerals of the Precambrian.
Archean rocks do not contain organic remains. The most ancient remains of organisms are known only from the Upper Proterozoic, or Riphean, deposits.
There is reason to believe that the organic world on Earth arose long before the Riphean - in the Archean.
It is believed that in the Archaean unicellular microscopic organisms were widely developed, and possibly multicellular ones, but without a mineral skeleton. Numerous finds of various stromatolites of blue-green algae in Riphean sediments make it possible to divide the Ripheans into four complexes.
Precambrian rocks, in addition to iron ores, which form large deposits not only in Russia (Kursk Magnetic Anomaly, Kola Peninsula and Karelia, Aldan Shield, etc.), but throughout the world, also contain other ore minerals: primary gold deposits on the Aldan Shield and Yenisei meganticlinorium, copper ores, rare elements, etc. Among non-metallic minerals - mica deposits on the Aldan shield. Widely used as building materials have granites, labradorites, marbles.
4. History of the development of the Earth in the early Paleozoic.
Cambrian period.
At the beginning of the Cambrian period, in connection with the complete end of Baikal tectogenesis, the contours of the ancient and epi-Baikal platforms were finally determined.
By the beginning of the Paleozoic era, shields and slabs were clearly visible on all ancient platforms.
Thus, a large Moscow syneclise is being laid on the East European Platform. On the Siberian Platform, the formation of the very large Tunguska syneclise dates back to the same time. The process of formation of syneclises on ancient platforms is accompanied by the appearance of deep foundation faults in the body of the platform.
The ancient platforms that emerged towards the end of the Precambrian were separated from one another by geosynclinal belts. Between the East European and South China platforms on one side and Gondwana on the other, there was a vast Mediterranean geosynclinal belt. Between the East European and Siberian platforms and between the Siberian and North China platforms stretched a knee-shaped, extensive Ural-Mongolian geosynclinal belt. The North American and East European platforms were separated by the Atlantic geosynclinal belt. The Arctic geosynclinal belt stretches north of the North American Platform. Two geosynclinal belts of enormous length (as in the modern era) bordered the depression Pacific Ocean: East Pacific - along the American Pacific coast and Western Pacific - along the Asian coast; they are often considered as a single Pacific geosynclinal belt.
One of the main features of the paleography of the Cambrian period is the fairly widespread development of the marine regime on the platforms of the Northern Hemisphere, while the Gondwanan continent was overwhelmingly characterized by a continental regime.
In geosynclinal belts, underwater and surface volcanism, as well as intrusive magmatism, represented by ultrabasic and basic rocks, and at subsequent stages of magmatism - granitoids, vigorously occurred.
Ordovician period.
During the Ordovician period, the same platforms and geosynclinal belts existed as at the end of the Cambrian period.
By the end of the period, in some geosynclinal troughs, the actual geosynclinal stage of development came to an end and was replaced by the orogenic stage (in the Northern Tien Shan and other structures of the Ural-Mongolian geosynclinal belt, the Appalachian and Grampian geosynclinal regions in the Atlantic geosynclinal belt).
During the Ordovician, the structure of the platforms shows a further deepening of ancient syneclises and the formation of new depressions.
Towards the end of the period, due to mountain building, a reduction in geosynclinal and epicontinental seas occurs in a number of geosynclinal systems.
Magmatic activity in mobile, geosynclinal zones is active. The presence of ultramafic rocks, as well as granitoid intrusions, is noted.
Silurian.
The Silurian period is the final period of manifestation of the Caledonian tectonic stage of the development of the earth's crust.
In the areas of Caledonian consolidation, there are so-called inherited troughs and superimposed depressions, in which, throughout the Devonian - Permian, peculiar rock formations accumulated, and only after that the platform stage of development began in them.
Areas of Caledonian consolidated structures are most clearly identified in the Atlantic geosynclinal belt, especially within the Grampian geosynclinal region (Scandinavian Mountains, the northern part of the British Islands, the western part of the Spitsbergen Islands, the eastern tip of Greenland), partially in the Appalachian geosynclinal region, and in the form of vast territories in the Urals. Mongolian geosynclinal belt (Sayan Mountains, Central Kazakhstan, Northern Tien Shan, Severnaya Zemlya) and in the Western Pacific geosynclinal belt (Kathasian geosynclinal region - east of the South China Platform, Australian geosynclinal region - west of the arc of the Australian Cordillera).
The formation of vast consolidated areas in the Grampian geosynclinal region caused the reunification of the East European and North American platforms into one vast continent called the North Atlantic.
Under the influence of Caledonian tectogenesis, deep faults appear in the foundation of a number of platforms, and the deepening of syneclises and the formation of depressions continues.
At the beginning of the Silurian period, after a relatively small Ordovician regression, a sea transgression occurred again, almost equal in scale to the Ordovician, and in approximately the same areas. However, in the second half of the period, in connection with the completion of the Caledonian stage of development, extensive uplifts occurred both in geosynclinal belts and on platforms. As a result, regressions develop, and many areas of the platforms are not only drained, but for a long time, for entire periods, they acquire a continental development regime.
According to modern ideas, it is 4.5 - 5 billion years old. In the history of its occurrence, planetary and geological stages are distinguished.
Geological stage- sequence of events in the development of the Earth as planets since the formation of the earth's crust. During it, relief forms arose and were destroyed, the land submerged under water (the advance of the sea), the retreat of the sea, glaciations, the appearance and disappearance of various types animals and plants, etc.
Scientists, trying to reconstruct the history of the planet, study rock layers. They divide all deposits into 5 groups, distinguishing the following eras: Archean (ancient), Proterozoic (early), Paleozoic (ancient), Mesozoic (middle) and Cenozoic (new). The border between eras passes through the largest evolutionary events. The last three eras are divided into periods, since in these deposits the remains of animals and plant remains were better preserved and in greater quantity.
Each era is characterized by events that had a decisive influence on modern life. relief.
Archean era was distinguished by violent volcanic activity, as a result of which igneous granite-containing rocks appeared on the surface of the Earth - the basis of future continents. At that time, the Earth was inhabited only by microorganisms that could live without oxygen. It is believed that the sediments of that era cover individual areas of land with an almost continuous shield; they contain a lot of iron, gold, silver, platinum and ores of other metals.
IN Proterozoic era Volcanic activity was also high, and mountains of the so-called Baikal fold were formed. They have practically not been preserved and now represent only isolated small uplifts on the plains. During this period, the planet was inhabited by blue-green algae and protozoan microorganisms, and the first multicellular organisms arose. Proterozoic rock layers are rich in minerals: iron ores and ores of non-ferrous metals, mica.
At first Paleozoic era formed mountains Caledonian folding, which led to the reduction of sea basins and the emergence of large areas of land. Only isolated ridges of the Urals, Arabia, Southeast China and Central Europe have been preserved in the form of mountains. All these mountains are low, “worn out”. In the second half of the Paleozoic, the mountains of the Hercynian fold were formed. This era of mountain building was more powerful; vast mountain ranges arose in the territory Western Siberia and the Urals, Mongolia and Manchuria, most of Central Europe, the east coast of North America and Australia. Now they are represented by low blocky mountains. In the Paleozoic era, the Earth was inhabited by fish, amphibians and reptiles, and algae predominated among the vegetation. The main deposits of oil and coal arose during this period.
Mesozoic era began with a period of relative calm internal forces Earth, the gradual destruction of previously created mountain systems and the immersion of flattened plain areas, for example, most of Western Siberia. In the second half of the era, mountains of Mesozoic folding were formed. At this time, vast mountainous countries appeared, which even now have the appearance of mountains. These are the Cordillera, the mountains of Eastern Siberia, certain parts of Tibet and Indochina. The ground was covered with lush vegetation, which gradually died and rotted. In a hot and humid climate, swamps and peat bogs were actively formed. This was the age of the dinosaurs. Giant predatory and herbivorous animals have spread throughout almost the entire planet. The first mammals appeared at this time.
Cenozoic era continues to this day. Its beginning was marked by an increase in the activity of the Earth's internal forces, which led to a general rise of the surface. During the era of Alpine folding, young folded mountains arose within the Alpine-Himalayan belt and the continent of Eurasia acquired its modern shape. In addition, there was a rejuvenation of the ancient mountain ranges of the Urals, Appalachians, Tien Shan, and Altai. The climate on the planet changed sharply, and a period of powerful ice sheets began. Ice sheets advancing from the north changed the topography of the continents of the Northern Hemisphere, forming hilly plains with a large number of lakes.
The entire geological history of the Earth can be traced on a geochronological scale - a table of geological time, showing the sequence and subordination of the main stages of geology, the history of the Earth and the development of life on it (see Table 4 on pp. 46-49). The geochronological table should be read from bottom to top.
Questions and tasks to prepare for the exam
1. Explain why polar days and nights are observed on Earth.
2. What would conditions be like on Earth if its axis of rotation were not inclined to the orbital plane?
3. The change of seasons on Earth is determined by two main reasons: the first is the rotation of the Earth around the Sun; name the second one.
4. How many times a year and when is the Sun at its zenith above the equator? Over the Northern Tropic? Over the South Tropic?
5. In what direction do constant winds and sea currents moving in the meridional direction deviate in the Northern Hemisphere?
6. When is the shortest night in the Northern Hemisphere?
7. What are the characteristics of the days of the spring and autumn equinoxes on Earth? When do they occur in the Northern and Southern Hemispheres?
8. When are the summer and winter solstices in the Northern and Southern Hemispheres?
9. In what light zones is the territory of our country located?
10. List the geological periods of the Cenozoic era, starting with the most ancient.
Table 4
Geochronological scale
| Eras (duration - in million years) | Periods (duration in million years) | The most important events in the history of the Earth | Characteristic minerals formed at this time |
| 1 | 2 | 3 | 4 |
| Cenozoic 70 million years | Quaternary 2 Ma (Q) | General rise of land. Repeated glaciations, especially in the Northern Hemisphere. The emergence of man | Peat, placer deposits of gold, diamonds, precious stones |
| Neogene 25 Ma (N) | The emergence of young mountains in areas of Alpine folding. Rejuvenation of mountains in areas of all ancient folds. Dominance of flowering plants | Brown coals, oil, amber | |
| Paleogene 41 Ma (P) | Destruction of the mountains of Mesozoic folding. Widespread development of flowering plants, birds and mammals | Phosphorites, brown coals, bauxites |
| Mesozoic 165 Ma | Cretaceous 70 Ma (K) | The emergence of young mountains in areas of Mesozoic folding. Extinction of giant reptiles (dinosaurs). Development of birds and mammals | Oil, oil shale, chalk, coal, phosphorites |
| Jurassic 50 Ma (J) | Formation of modern oceans. Hot and humid climate over most of the land. The rise of giant reptiles (dinosaurs). Dominance of gymnosperms | Hard coals, oil, phosphorites | |
| Triassic 40 Ma (T) | The greatest retreat of the sea and rise of land in the entire history of the Earth. Destruction of the mountains of the Caledonian and Hercynian folds. Vast deserts. First mammals | Rock salts | |
| 1 | 2 | 3 | 4 |
| Paleozoic 330 million years | Permian 45 Ma (P) | The emergence of young folded mountains in the areas of the Hercynian fold. Dry climate over most of the land. The emergence of gymnosperms | Rock and potassium salts, gypsum |
| Carboniferous 65 Ma (C) | Hot and humid climate over most of the land. Widespread marshy lowlands in coastal areas. Forests of tree ferns. The first reptiles, the rise of amphibians | Coal, oil | |
| Devonian 55 Ma (p) | Hot climate on most of the land. The first deserts. The appearance of amphibians. Numerous fish | Salts, oil | |
| Silurian 35 Ma (S) | The emergence of young folded mountains in the areas of the Caledonian folding. The first land plants (mosses and ferns) | |
| | Ordovician 60 Ma (O) | Reducing the area of sea basins. Appearance of the first terrestrial invertebrates | |
| Cambrian 70 Ma | The emergence of young mountains in the areas of the Baikal fold. Flooding of vast areas by seas. The flourishing of marine invertebrates | Rock salt, gypsum, phosphorites | |
| Proterozoic era 600 million years | The beginning of the Baikal folding. Powerful volcanism. Development of bacteria and blue-green algae | Iron ores, mica, graphite | |
| Archean era 900 million years | Formation of the continental crust. Intense volcanic activity. The time of primitive single-celled bacteria | Ore | |
Maksakovsky V.P., Petrova N.N., Physical and economic geography of the world. - M.: Iris-press, 2010. - 368 pp.: ill.
Lesson content lesson notes supporting frame lesson presentation acceleration methods interactive technologies Practice tasks and exercises self-test workshops, trainings, cases, quests homework discussion questions rhetorical questions from students Illustrations audio, video clips and multimedia photographs, pictures, graphics, tables, diagrams, humor, anecdotes, jokes, comics, parables, sayings, crosswords, quotes Add-ons abstracts articles tricks for the curious cribs textbooks basic and additional dictionary of terms other Improving textbooks and lessonscorrecting errors in the textbook updating a fragment in a textbook, elements of innovation in the lesson, replacing outdated knowledge with new ones Only for teachers perfect lessons calendar plan for the year guidelines discussion programs Integrated LessonsIt should not be identified with the unit of time adopted in our chronology: this is not a hundred years at all, but that indefinite period of time during which the deposition of organic remains of certain species of animals and plants in layers took place (more details:). Sediments in the layers of the Earth.
Geological units
For the convenience of studying it, the history of the Earth is divided into large periods of time:- these intervals are called eras;
- eras are divided into periods;
- periods for eras;
- era - on century.
- during an era called group;
- corresponds to the period sediment system;
- era - Department;
- century - tier.
The sequence of geological units in time is conveyed by the following summary table:
| Era (groups) | Periods (systems) | Average duration of periods (million years) |
|
Cenozoic (Cenozoic) - 77 million years |
Quaternary | 1 |
| Upper Tertiary (Neogene) | 24 | |
| Lower Tertiary (Paleogene) | 45 | |
| Mesozoic (Mesozoic) - 120 million years | Cretaceous (chalk) | 40 |
| Jurassic (Jurassic) | 40 | |
| Triassic (Triassic) | 35 | |
| Paleozoic (Paleozoic) - 325 million years | Perm (Perm) | 40 |
| Carboniferous (carbon) | 50 | |
| Devonian (Devonian) | 35 | |
| Silurian (Silurian) | 35 | |
| Ordovician (Ordovician) | 85 | |
| Cambrian (Cambrian) | 80 | |
| Proterozoic era (Proterozoic) Archaeozoic era (Archaeozoic) | Precambrian | 700 1500 |
- The Archeozoic era is the most ancient era, the beginning of life;
- Proterozoic - era of primary life;
- Paleozoic - ancient life;
- Mesozoic - average lifespan;
- Cenozoic - new life.
- archaeozoic,
- Proterozoic,
- Paleozoic,
- Mesozoic,
- Cenozoic
- primary (Paleozoic),
- secondary (Mesozoic),
- Tertiary (Cenozoic).
Rock deposits. The names of these periods are not entirely appropriate, since chalk deposits and especially coal deposits are found not only among the deposits of these periods. - The Jurassic period, otherwise known as the Jurassic, received its name from the mountains where the deposits of this system were first studied in detail (French and Swiss Jura);
- Triassic (in Greek “trias” - trinity) fully corresponds to the division of deposits of this system into three sections;
- Permian - according to the ancient Finno-Ugric kingdom of Permia, on whose territory in the former Perm province deposits of this system were discovered for the first time;
- Devonian - from the province of Devonshire;
- Silurian - from the name of the ancient inhabitants of the province of Wales - the Silurians;
- Ordovician - also from the ancient tribe of Ordovicians, neighbors of the Silurians;
- Cambrian - from ancient name the province of Wales itself - Cambria.
Geological maps
Thorough research into the outputs earth's surface deposits of certain systems allows us to compile geological maps. Although they are based on a geographical contour with a modern outline of the land, with the designation of many rivers and points of cities, they are sharply different from ordinary geographical maps, well known to everyone! A person not experienced in geological science is amazed by their variegation of colors and whimsical patterns, like on a carpet. There are so many colors here: green, blue, yellow, orange, red, gray in various tones! Various letters, icons, whimsically curved lines. How to understand them?
Geological map. There is nothing fancy here: each color of the geological map is associated with sediments of a certain system. For example, gray color of various shades is associated with Carboniferous deposits of different ages: Lower Carboniferous, Middle Carboniferous and Upper Carboniferous sections. Blue color is Jurassic deposits, green is Cretaceous, yellow is Tertiary. It is not difficult to understand letter designations cards: - A - this is Archeozoic and Proterozoic, otherwise Precambrian,
- P - Permian system, otherwise - Perm,
- T - Triassic,
- C - coal, etc.
No, the colors on our map are not scattered in disorder and chaos, but obedient to the great laws of physics and chemistry that govern the world and us,- said the academician A. E. Fersman. The name of the first Soviet president of the USSR Academy of Sciences is especially closely associated with the geological map - A. P. Karpinsky(1847-1936), who is rightly called the “father of Russian geology.” He compiled the first geological map of Russia in 1892, and before that time Russian geologists had to use the old map compiled in the forties of the last century by an English explorer of Russia, the famous geologist Murchison. On the maps of the most ancient periods of the life of the Earth, called paleogeographic, A.P. Karpinsky seems to resurrect before us pictures of the distant past, pictures of the eternal change of land and sea in the vast expanses of Eurasia. A.P. Karpinsky also made a valuable contribution to the study of rocks and minerals. His works are widely implemented, and at present modern theology, following the paths outlined by the “father of Russian geology”, has great importance in world science.