Geological time and methods for its determination

In the study of the Earth as a unique cosmic object, the idea of ​​its evolution occupies a central place, therefore an important quantitative-evolutionary parameter is geological time. This time is studied by a special science called Geochronology– geological chronology. Geochronology May be absolute and relative.

Note 1

Absolute geochronology deals with determining the absolute age of rocks, which is expressed in units of time and, as a rule, in millions of years.

The determination of this age is based on the decay rate of isotopes of radioactive elements. This speed is a constant value and depends on the intensity of physical and chemical processes does not depend. Age determination is based on nuclear physics methods. Minerals containing radioactive elements, when forming crystal lattices, form a closed system. In this system, the accumulation of radioactive decay products occurs. As a result, the age of a mineral can be determined if the rate of this process is known. The half-life of radium, for example, is $1590$ years, and the complete decay of the element will occur in $10$ times the half-life. Nuclear geochronology has its leading methods - lead, potassium-argon, rubidium-strontium and radiocarbon.

Methods of nuclear geochronology made it possible to determine the age of the planet, as well as the duration of eras and periods. Radiological time measurement proposed P. Curie and E. Rutherford at the beginning of the $XX$ century.

Relative geochronology operates with such concepts as “early age, middle age, late age.” There are several developed methods for determining the relative age of rocks. They are combined into two groups - paleontological and non-paleontological.

First play a major role due to their versatility and widespread use. The exception is the absence of organic remains in the rocks. Using paleontological methods, the remains of ancient extinct organisms are studied. Each rock layer is characterized by its own complex of organic remains. In each young layer there will be more remains of highly organized plants and animals. The higher the layer lies, the younger it is. A similar pattern was established by the Englishman W. Smith. He owned the first geological map of England, on which rocks were divided by age.

Non-paleontological methods determinations of the relative age of rocks are used in cases where they lack organic remains. More effective then will be stratigraphic, lithological, tectonic, geophysical methods. Using the stratigraphic method, it is possible to determine the sequence of bedding of layers during their normal occurrence, i.e. the underlying strata will be older.

Note 3

The sequence of rock formation determines relative geochronology, and their age in time units is already determined absolute geochronology. Task geological time is to define chronological sequence geological events.

Geochronological table

To determine the age of rocks and study them, scientists use various methods, and for this purpose a special scale has been compiled. Geological time on this scale is divided into time intervals, each of which corresponds to a certain stage of formation earth's crust and development of living organisms. The scale was named geochronological table, which includes the following divisions: eon, era, period, epoch, century, time. Each geochronological unit is characterized by its own complex of sediments, which is called stratigraphic: eonothema, group, system, department, tier, zone. A group, for example, is a stratigraphic unit, and the corresponding temporary geochronological unit represents it era. Based on this, there are two scales - stratigraphic and geochronological. The first scale is used when talking about sediments, because at any period of time some geological events occurred on Earth. The second scale is needed to determine relative time. Since its adoption, the content of the scale has changed and been refined.

The largest stratigraphic units at present are eonothems - Archean, Proterozoic, Phanerozoic. On the geochronological scale, they correspond to zones of varying duration. According to the time of existence on Earth, they are distinguished Archean and Proterozoic eonothems, covering almost $80$% of the time. Phanerozoic eon in time is significantly shorter than the previous eons and covers only $570$ million years. This ionoteme is divided into three main groups - Paleozoic, Mesozoic, Cenozoic.

The names of eonothems and groups are of Greek origin:

• Archeos means the most ancient;
• Protheros – primary;
• Paleos – ancient;
• Mesos – average;
• Kainos is new.

From the word " zoiko s", which means vital, the word " zoy" Based on this, eras of life on the planet are distinguished, for example, the Mesozoic era means the era of average life.

Eras and periods

According to the geochronological table, the history of the Earth is divided into five geological eras: Archean, Proterozoic, Paleozoic, Mesozoic, Cenozoic. In turn, eras are divided into periods. There are significantly more of them - $12$. The duration of the periods varies from $20$-$100$ million years. The latter indicates its incompleteness Quaternary period of the Cenozoic era, its duration is only $1.8$ million years.

Archean era. This time began after the formation of the earth’s crust on the planet. By this time, there were mountains on Earth, and the processes of erosion and sedimentation came into play. The Archean lasted approximately $2$ billion years. This era is the longest in duration, during which volcanic activity was widespread on Earth, deep uplifts occurred, which resulted in the formation of mountains. Most of the fossils were destroyed under the influence of high temperature, pressure, and mass movement, but little data about that time was preserved. In rocks of the Archean era, pure carbon is found in dispersed form. Scientists believe that these are modified remains of animals and plants. If the amount of graphite reflects the amount of living matter, then there was a lot of it in the Archean.

Proterozoic era. This is the second era in duration, spanning $1$ billion years. Throughout the era, large amounts of sediment were deposited and one significant glaciation occurred. Ice sheets extended from the equator to $20$ degrees of latitude. Fossils found in the rocks of this time are evidence of the existence of life and its evolutionary development. Sponge spicules, remains of jellyfish, fungi, algae, arthropods, etc. were found in Proterozoic sediments.

Palaeozoic. Stands out in this era six periods:

• Cambrian;
• Ordovician,
• Silur;
• Devonian;
• Carbon or coal;
• Perm or Perm.

The duration of the Paleozoic is $370$ million years. During this time, representatives of all types and classes of animals appeared. There were only birds and mammals missing.

Mesozoic era. The era is divided into three period:

• Triassic;

The era began approximately $230$ million years ago and lasted $167$ million years. During the first two periods - Triassic and Jurassic– most of the continental regions rose above sea level. The climate of the Triassic was dry and warm, and in the Jurassic it became even warmer, but was already humid. In state Arizona there is a famous stone forest that has existed since Triassic period. True, all that was left of the once mighty trees were trunks, logs and stumps. At the end of the Mesozoic era, or more precisely in the Cretaceous period, a gradual advance of the sea occurred on the continents. The North American continent sank at the end of the Cretaceous period and, as a result, the waters of the Gulf of Mexico connected with the waters of the Arctic basin. The mainland was divided into two parts. The end of the Cretaceous period is characterized by a large uplift, called Alpine orogeny. At this time, the Rocky Mountains, Alps, Himalayas, and Andes appeared. Intense volcanic activity began in western North America.

Cenozoic era. This new era, which has not yet ended and is currently ongoing.

The era was divided into three periods:

• Paleogene;
• Neogene;
• Quaternary.

Quaternary period has whole line unique features. This is the time of the final formation of the modern face of the Earth and the ice ages. Became independent New Guinea and Australia, moving closer to Asia. Antarctica remained in its place. Two Americas united. Of the three periods of the era, the most interesting is quaternary period or anthropogenic. It continues today, and was isolated in $1829 by a Belgian geologist J. Denoyer. Cold snaps are replaced by warming spells, but its most important feature is appearance of man.

Modern man lives in the Quaternary period of the Cenozoic era.

The history of planet Earth already goes back approximately 7 billion years. During this time our common Home has undergone significant changes, which was a consequence of changing periods. in chronological order they reveal the entire history of the planet from its very appearance to the present day.

Geological chronology

The history of the Earth, presented in the form of eons, groups, periods and eras, is a certain grouped chronology. At the first international congresses of geology, a special chronological scale was developed, which represented the periodization of the Earth. Subsequently, this scale was replenished new information and changed, as a result, now it reflects all geological periods in chronological order.

The largest divisions on this scale are eonothems, eras and periods.

Formation of the Earth

The geological periods of the Earth in chronological order begin their history precisely with the formation of the planet. Scientists have concluded that the Earth was formed approximately 4.5 billion years ago. The process of its formation itself was very long and may have begun 7 billion years ago from small cosmic particles. Over time, the gravitational force grew, and along with it, the speed of the bodies falling onto the forming planet increased. Kinetic energy was transformed into heat, resulting in a gradual warming of the Earth.

The Earth's core, according to scientists, was formed over several hundred million years, after which the gradual cooling of the planet began. Currently, the molten core contains 30% of the Earth's mass. The development of other shells of the planet, according to scientists, has not yet been completed.

Precambrian eon

In the geochronology of the Earth, the first eon is called the Precambrian. It covers the time 4.5 billion - 600 million years ago. That is, the lion's share of the planet's history is covered by the former. However, this eon is divided into three more - Katarchean, Archean, Proterozoic. Moreover, often the first of them stands out as an independent eon.

At this time, the formation of land and water occurred. All this happened during active volcanic activity for almost the entire eon. The shields of all continents were formed in the Precambrian, but traces of life are very rare.

Catarchaean Eon

The beginning of the history of the Earth - half a billion years of its existence in science is called catarchaeum. The upper limit of this eon is located at around 4 billion years ago.

Popular literature portrays catarchaea as a time of active volcanic and geothermal changes on the Earth's surface. However, in reality this is not true.

The Catarchaean Eon is a time when volcanic activity did not manifest itself, and the surface of the Earth was a cold, inhospitable desert. Although earthquakes occurred quite often, which smoothed the landscape. The surface looked like dark gray primordial material covered with a layer of regolith. A day at that time was only 6 hours long.

Archean eon

The second main eon of four in the history of the Earth lasted about 1.5 billion years - 4-2.5 billion years ago. At that time, the Earth did not yet have an atmosphere, therefore there was no life yet, however, during this eon, bacteria appeared; due to the lack of oxygen, they were anaerobic. As a result of their activities, today we have deposits of natural resources such as iron, graphite, sulfur and nickel. The history of the term “archaea” dates back to 1872, when it was proposed by the famous American scientist J. Dan. The Archean eon, unlike the previous one, is characterized by high volcanic activity and erosion.

Proterozoic eon

If we consider geological periods in chronological order, the next billion years were occupied by the Proterozoic. This period is also characterized by high volcanic activity and sedimentation, and erosion continues over vast areas.

The formation of the so-called occurs. mountains Currently they are small hills on the plains. The rocks of this eon are very rich in mica, non-ferrous metal ores and iron.

It should be noted that in the Proterozoic period the first living creatures appeared - simple microorganisms, algae and fungi. And by the end of the eon, worms, marine invertebrates, and mollusks appear.

Phanerozoic eon

All geological periods in chronological order can be divided into two types - obvious and hidden. Phanerozoic belongs to the obvious ones. At this time it appears a large number of living organisms with mineral skeletons. The era preceding the Phanerozoic was called hidden because practically no traces of it were found due to the lack of mineral skeletons.

The last about 600 million years of the history of our planet are called the Phanerozoic eon. The most significant events of this eon are the Cambrian explosion, which occurred approximately 540 million years ago, and the five largest extinctions in the history of the planet.

Eras of the Precambrian Eon

During the Katarchean and Archean there were no generally recognized eras and periods, so we will skip their consideration.

The Proterozoic consists of three large eras:

Paleoproterozoic- i.e. ancient, including the Siderian, Rhiasian period, Orosirium and Staterium. By the end of this era, oxygen concentrations in the atmosphere had reached modern levels.

Mesoproterozoic- average. Consists of three periods - potassium, ectasia and sthenia. During this era, algae and bacteria reached their greatest prosperity.

Neoproterozoic- new, consisting of Thonium, Cryogenium and Ediacaran. At this time, the formation of the first supercontinent, Rodinia, occurred, but then the plates diverged again. The coldest ice age occurred during an era called the Mesoproterozoic, during which much of the planet froze.

Eras of the Phanerozoic eon

This eon consists of three large eras, sharply different from each other:

Paleozoic, or the era of ancient life. It began approximately 600 million years ago and ended 230 million years ago. The Paleozoic consists of 7 periods:

1. Cambrian (a temperate climate was formed on Earth, the landscape was low-lying, during this period the birth of all modern types animals).
2. Ordovician (the climate throughout the planet is quite warm, even in Antarctica, while the land subsides significantly. The first fish appear).
3. Silurian period (large inland seas are formed, while the lowlands become drier due to the rise of land. The development of fish continues. The Silurian period is marked by the appearance of the first insects).
4. Devonian (appearance of the first amphibians and forests).
5. Lower Carboniferous (dominance of pteridophytes, distribution of sharks).
6. Upper and Middle Carboniferous (appearance of the first reptiles).
7. Perm (most ancient animals die out).

Mesozoic, or the time of reptiles. Geological history consists of three periods:

1. Triassic (seed ferns die out, gymnosperms dominate, the first dinosaurs and mammals appear).
2. Jurassic (part of Europe and western America covered with shallow seas, appearance of the first toothed birds).
3. Chalk (appearance of maple and oak forests, the highest development and extinction of dinosaurs and toothed birds).

Cenozoic, or the time of mammals. Consists of two periods:

1. Tertiary. At the beginning of the period, predators and ungulates reach their dawn, the climate is warm. There is a maximum expansion of forests, the oldest mammals are dying out. Approximately 25 million years ago, humans appeared and in the Pliocene era.
2. Quaternary. Pleistocene - large mammals die out, human society emerges, 4 ice ages occur, many plant species become extinct. Modern era- the last ice age ends, the climate gradually takes on its current form. The primacy of man on the entire planet.

The geological history of our planet has a long and contradictory development. In this process, there were several extinctions of living organisms, ice ages were repeated, periods of high volcanic activity were observed, and there were eras of dominance of different organisms: from bacteria to humans. The history of the Earth began approximately 7 billion years ago, it was formed about 4.5 billion years ago, and just less than a million years ago, man ceased to have competitors in all living nature.

We present to your attention an article about the classical understanding of the development of our planet Earth, written in a non-boring way, understandable and not too long..... If any of the older people have forgotten, it will be interesting to read, well, for those who are younger, and even for an abstract, it’s generally excellent material .

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 they rushed through this substance at great speed. spaceships with representatives of the universal mind. 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 solar system. And after the star appeared, the planets appeared. One of them was ours motherland. 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.

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 approximately 3.5 billion years back.


• The second stage began approximately 540 million years back. 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’s development, 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. At the time of the Katarchaean there was neither the earth's crust nor the core. The planet was a cold cosmic body. The temperature in its depths corresponded to the melting point of the substance. On top, 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:

• Eoarchaean


• paleoarchean


• mesoarchaean


• neoarchaean

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 low content nitrogen. There was no oxygen. At the end of this era of Earth's development, 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 present 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 this, the atmosphere was dominated by 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. It was very important stage 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 such an era of the Earth's development as potassium, the supercontinent Columbia 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:

• Thonium (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. Last period 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)


• 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. 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's development 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 greatly damaged swipe, 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. Subsequently, it connected with the Asian plate, but the collision was so severe 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)


• 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 enormous power. 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 average duration 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.

Life on Earth began over 3.5 billion years ago, immediately after the completion of the formation of the earth's crust. Throughout time, the emergence and development of living organisms influenced the formation of relief and climate. Also, tectonic and climatic changes that have occurred over many years have influenced the development of life on Earth.

A table of the development of life on Earth can be compiled based on the chronology of events. The entire history of the Earth can be divided into certain stages. The largest of them are eras of life. They are divided into eras, eras into periods, periods -per era, eras - for centuries.

Eras of life on Earth

The entire period of the existence of life on Earth can be divided into 2 periods: the Precambrian, or cryptozoic (primary period, 3.6 to 0.6 billion years), and the Phanerozoic.

The Cryptozoic includes the Archean (ancient life) and Proterozoic (primary life) eras.

The Phanerozoic includes the Paleozoic (ancient life), Mesozoic (middle life) and Cenozoic (new life) eras.

These 2 periods of life development are usually divided into smaller ones - eras. The boundaries between eras are global evolutionary events, extinctions. In turn, eras are divided into periods, and periods into epochs. The history of the development of life on Earth is directly related to changes in the earth’s crust and the planet’s climate.

Eras of development, countdown

The most significant events are usually identified in special time intervals - eras. Time is counted down in reverse order, from ancient life to modern life. There are 5 eras:

Periods of development of life on Earth

The Paleozoic, Mesozoic and Cenozoic eras include periods of development. These are smaller periods of time compared to eras.

• Cambrian (Cambrian).
• Ordovician.
• Silurian (Silurian).
• Devonian (Devonian).
• Carboniferous (carbon).
• Perm (Perm).

• Lower Tertiary (Paleogene).
• Upper Tertiary (Neogene).
• Quaternary, or Anthropocene (human development).

The first 2 periods are included in the Tertiary period lasting 59 million years.

Proterozoic era (early life)

6. Perm (Perm)

2. Upper Tertiary (Neogene)

3. Quaternary or Anthropocene (human development)

Development of living organisms

The table of the development of life on Earth involves division not only into time periods, but also into certain stages of the formation of living organisms, possible climate changes (ice age, global warming).

• Archean era. The most significant changes in the evolution of living organisms are the appearance of blue-green algae - prokaryotes capable of reproduction and photosynthesis, and the emergence of multicellular organisms. The appearance of living protein substances (heterotrophs) capable of absorbing organic substances dissolved in water. Subsequently, the appearance of these living organisms made it possible to divide the world into plant and animal.

• Mesozoic era.

• Triassic. Distribution of plants (gymnosperms). Increase in the number of reptiles. The first mammals, bony fish.
• Jurassic period. The predominance of gymnosperms, the emergence of angiosperms. The appearance of the first bird, the flourishing of cephalopods.
• Cretaceous period. Distribution of angiosperms, decline of other plant species. Development of bony fishes, mammals and birds.

• Cenozoic era.
  • Lower Tertiary period (Paleogene). The rise of angiosperms. Development of insects and mammals, appearance of lemurs, later primates.
  • Upper Tertiary period (Neogene). The formation of modern plants. The appearance of human ancestors.
  • Quaternary period (Anthropocene). Formation of modern plants and animals. The appearance of man.

Development of inanimate conditions, climate change

The table of the development of life on Earth cannot be presented without data on changes in inanimate nature. The emergence and development of life on Earth, new species of plants and animals, all this is accompanied by changes in inanimate nature and climate.

Climate Change: Archean Era

The history of the development of life on Earth began through the stage of dominance of land over water resources. The relief was poorly outlined. The atmosphere is dominated by carbon dioxide, the amount of oxygen is minimal. Shallow waters have low salinity.

The Archean era is characterized by volcanic eruptions, lightning, and black clouds. The rocks are rich in graphite.

Climatic changes in the Proterozoic era

The land is a rocky desert; all living organisms live in water. Oxygen accumulates in the atmosphere.

Climate Change: Paleozoic Era

At various periods of the Paleozoic era there were following changes climate:

• Cambrian period. The land is still deserted. The climate is hot.
• Ordovician period. The most significant changes are the flooding of almost all northern platforms.
• Silurian. Tectonic changes and conditions of inanimate nature are varied. Mountain formation occurs and the seas dominate the land. Areas of different climates, including areas of cooling, have been identified.
• Devonian. The climate is dry and continental. Formation of intermountain depressions.
• Carboniferous period. Subsidence of continents, wetlands. The climate is warm and humid, with a lot of oxygen and carbon dioxide in the atmosphere.
• Permian period. Hot climate, volcanic activity, mountain building, drying out of swamps.

During the Paleozoic era, the Caledonian fold mountains were formed. Such changes in relief affected the world's oceans - sea basins shrank and a significant land area formed.

The Paleozoic era marked the beginning of almost all major oil and coal deposits.

Climatic changes in the Mesozoic

The climate of different periods of the Mesozoic is characterized by the following features:

• Triassic. Volcanic activity, climate is sharply continental, warm.
• Jurassic period. Mild and warm climate. The seas dominate the land.
• Cretaceous period. Retreat of the seas from the land. The climate is warm, but at the end of the period global warming gives way to cooling.

In the Mesozoic era, previously formed mountain systems are destroyed, the plains go under water ( Western Siberia). In the second half of the era, the Cordilleras, mountains Eastern Siberia, Indochina, partly Tibet, mountains of Mesozoic folding were formed. The prevailing climate is hot and humid, promoting the formation of swamps and peat bogs.

Climate Change - Cenozoic Era

During the Cenozoic era, a general rise of the Earth's surface occurred. The climate has changed. Numerous glaciations of the earth's surfaces advancing from the north changed the appearance of the continents of the Northern Hemisphere. Thanks to such changes, the hilly plains were formed.

• Lower Tertiary period. Mild climate. Division into 3 climatic zones. Formation of continents.
• Upper Tertiary period. Dry climate. The emergence of steppes and savannas.
• Quaternary period. Multiple glaciations of the northern hemisphere. Cooling climate.

All changes during the development of life on Earth can be written down in the form of a table that will reflect the most significant stages in the formation and development modern world. Despite the already known research methods, even now scientists continue to study history, making new discoveries that allow modern society find out how life developed on Earth before the advent of man.

Development of life on Earth lasts more than 3 billion years. And this process continues to this day.

The first living things in the Archaean were bacteria. Then single-celled algae, animals and fungi appeared. Multicellular organisms replaced unicellular organisms. At the beginning of the Paleozoic, life was already very diverse: representatives of all types of invertebrates lived in the seas, and the first land plants appeared on land. In the following eras, over the course of many millions of years, different groups of plants and animals formed and died out. Gradually the living world became more and more similar to the modern one.

2.6. History of life development

Previously, scientists believed that living things came from living things. Bacterial spores were brought from space. Some bacteria created organic substances, others consumed and destroyed them. As a result, an ancient ecosystem arose, the components of which were connected by the cycle of substances.

Modern scientists have proven that living things came from inanimate nature. In the aquatic environment, organic substances were formed from inorganic substances under the influence of the energy of the Sun and the internal energy of the Earth. From them the most ancient organisms - bacteria - were formed.

In the history of the development of life on Earth, several eras are distinguished.

Archaea

The first organisms were prokaryotes. In the Archean era, a biosphere already existed, consisting mainly of prokaryotes. The very first living creatures on the planet are bacteria. Some of them were capable of photosynthesis. Photosynthesis was carried out by cyanobacteria (blue-green).

Proterozoic

As oxygen levels increased in the atmosphere, eukaryotic organisms began to appear. In the Proterozoic, unicellular plants arose in the aquatic environment, and then unicellular animals and fungi. An important event The Proterozoic was the emergence of multicellular organisms. By the end of the Proterozoic, various types of invertebrates and chordates had already appeared.

Paleozoic

Plants

Gradually, dry land arose in place of the warm, shallow seas. As a result, the first land plants evolved from multicellular green algae. In the second half of the Paleozoic, forests appeared. They consisted of ancient ferns, horsetails and mosses, which reproduced by spores.

Animals

At the beginning of the Paleozoic, marine invertebrates flourished. Vertebrate animals - armored fish - developed and spread in the seas.

In the Paleozoic, the first terrestrial vertebrates appeared - the oldest amphibians. From them at the end of the era the first reptiles originated.

The most numerous in the seas of the Paleozoic (era of ancient life) were trilobites - fossil arthropods that looked like giant woodlice. Trilobites - existed at the beginning of the Paleozoic, completely died out 200 million years ago. They swam and crawled in shallow bays, feeding on plants and animal remains. There is an assumption that there were predators among the trilobites.

The very first animals to colonize land were arachnids and giant flying insects - the ancestors of modern dragonflies. Their wingspan reached 1.5 m.

Mesozoic

During the Mesozoic, the climate became drier. The ancient forests gradually disappeared. Spore-bearing plants were replaced by plants that reproduce by seeds. Among animals, reptiles, including dinosaurs, flourished. At the end of the Mesozoic, many species of ancient seed plants and dinosaurs became extinct.

Animals

The largest of the dinosaurs were brachiosaurs. They reached more than 30 m in length and weighed 50 tons. These dinosaurs had a huge body, long tail and neck, and a small head. If they lived in our time, they would be taller than five-story buildings.

Plants

The most complexly organized plants are flowering plants. They appeared in the middle of the Mesozoic (the era of middle life). Material from the site http://wikiwhat.ru

Cenozoic

The Cenozoic is the heyday of birds, mammals, insects and flowering plants. In birds and mammals, due to the more advanced structure of organ systems, warm-bloodedness arose. They became less dependent on environmental conditions and spread widely on Earth.

Bones of dinosaurs and amazing extinct animals have been found in different eras human history. In the absence of science, legends about giants or dragons were formed from the bones found. Only modern people with the development of science were able to study the main stages of the development of life on Earth using paleontological finds.

Earth Education

Our planet was formed about 4.5 billion years ago from star dust and solid particles. As gravity increased, the Earth began to attract debris and rocks from space, which fell to the surface, gradually warming the planet. Over time, the top layer became denser and began to cool. The hot mantle maintains heat until now, preventing the Earth from turning into a block of ice.

For a long time the planet was in a lifeless state. The atmosphere was filled with various gases and did not contain oxygen. Due to the release of large amounts of steam from the bowels of the Earth and gravity, dense clouds began to form. Intense rains contributed to the emergence of the World Ocean, in which life originated.

Rice. 1. Formation of the Earth.

Oxygen appeared in the atmosphere with the appearance of the first photosynthetic plants.

Stages of development

Life on Earth is associated with geological eons and eras. An eon is a large segment of geological history that unites several eras. In turn, eras are divided into periods. Each era is characterized by the individual development of the animal and flora, which often depended on climate, the state of the earth’s crust, and underground activity.

Rice. 2. Eras of the geological history of the Earth.

A more detailed description of the eons is presented in the table of the main stages of the development of life on Earth.

TOP 1 articlewho are reading along with this

Eon	Era	Period	Characteristic
Katarhey			It began about 4.5 billion years ago and ended 4 billion years ago. Sedimentary rocks are unknown. The surface of the planet is lifeless and dotted with craters
			Lasted from 4 to 2.5 billion years ago. At the end of the Eoarchean the first single-celled organisms- anaerobic bacteria. Formation of carbonate deposits and minerals. Formation of continents. Oxygen is formed in the Neoarchaean thanks to cyanobacteria
	Paleoarchaean
	Mesoarchean
	Neoarchaean
Proterozoic	Paleoproterozoic		The period is from 2.5 to 1.6 billion years ago. More advanced cyanobacteria release large amounts of oxygen, which leads to an oxygen catastrophe. Oxygen becomes destructive for anaerobic organisms. The first aerobic eukaryotes arise in stateria
		Orosirium
		Staterius
	Mesoproterozoic		Lasted 1.6-1 billion years ago. Sedimentary rocks are formed. In ectasia, the first multicellular organisms appear - red algae. In sthenia, eukaryotes arise that reproduce sexually
	Neoproterozoic		It began 1 billion years ago and ended 542 million years ago. Severe glaciation of the earth's crust. The first multicellular soft-bodied animals—vendobionts—appear in the Ediacaran region.
		Cryogenium
		Ediacaran
Phanerozoic	Paleozoic		Lasted from 541 to 290 million years ago. At the beginning of the era, species diversity of living organisms appears. An extinction event occurred between the Ordovician and Silurian, as a result of which more than 60% of living beings disappeared, but already in the Devonian, life began to develop new ecological niches. Horsetails, ferns, gymnosperms, a large number of lobe-finned fish, the first vertebrate land animals, insects, spiders, and ammonites appeared. An extinction event also occurred at the end of the Devonian. In the Carboniferous, reptiles, amphibians, mollusks, bryozoans, arthropods, and cartilaginous fish appear. During the Permian period, beetles, lacewing insects, and predatory animals appeared
			It began 252 million years ago and ended 66 million years ago. At the junction of the Permian and Triassic, the largest mass extinction occurs, as a result of which 90% of sea ​​creatures and 70% terrestrial. In the Jurassic period, the first flowering plants appeared, displacing gymnosperms. Reptiles and insects occupy a dominant position. During the Cretaceous period there was a cooling and the extinction of most plants. This leads to the death of herbivores and then predatory reptiles. The first birds and mammals take their place
	Cenozoic	Paleogene	It began 66 million years ago and continues to this day. Variety of birds, plants, insects. Whales, sea urchins, cephalopods, elephants, and horses appear. In the Anthropocene - the current period - about 2 million years ago the first people (Homo) arose