Scale geochronological and the history of the development of living organisms

The stratigraphic scale (geochronological) is the standard with which the Earth's history is measured by time and geological magnitude. This scale is a kind of calendar that counts the time intervals in hundreds of thousands and even millions of years.

About the planet

Modern conventional views on the Earth are based on various data, according to which the age of our planet is approximately four and a half billion years. Neither rocks nor minerals that could testify to the formation of our planet have so far not been discovered either in the depths or on the surface. Refractory compounds, rich in calcium, aluminum and carbonaceous chondrites, which were formed in the solar system earlier all, limit the maximum age of the Earth to these figures. The stratigraphic scale (geochronological) shows the boundaries of time from the formation of the planet.

Various meteorites were studied using modern methods, including uranium-lead, and as a result, estimates of the age of the solar system are presented. As a result, the time elapsed since the creation of the planet was delineated into time intervals for the most important events for the Earth. The geochronological scale is very convenient for tracking geological times. The Phanerozoic Era, for example, is distinguished by the largest evolutionary events, when the global extinction of living organisms took place: the Paleozoic on the border with the Mesozoic was marked by the largest disappearance of species (permo-Triassic) in the history of the planet, and the end of the Mesozoic is separated from the Cenozoic by the extinction of Cretaceous-Paleogene.

History of creation

For the hierarchy and nomenclature of all modern units of geochronology, the nineteenth century turned out to be the most important: in its second half, the sessions of the International Geological Congress were held. After this, from 1881 to 1900, a modern stratigraphic scale was compiled.

Its geochronological "stuffing" was later refined and changed many times as new data were received. Absolutely different signs served as themes for specific names, but the most common factor is geographical.

Titles

For example, the Cambrian period is named so because Cambria is Wales during the Roman Empire, and the Devonian period is named after the county of Devonshire in England. The name of the Permian period came from the city of Perm, and the name Jurassic was given to the Jurassic. Ancient tribes - Lusatian Serbs (the Germans called them Vendians), served as the name of the Vendian period, and in memory of the Celts - tribes of Ordovics and Silurians - the Silurian and Ordovician periods were named .

The geochronological scale sometimes connects the names with the geological composition of the rocks: the coal appeared in connection with the huge number of coal seams during the excavations, and the chalky - just because the world has spread chalk.

Principle of construction

To determine the relative geological age of the rock, a special geochronological scale was needed. Era, periods, that is, the age that is measured in years, does not matter much to geologists. All the time of life of our planet was divided into two main segments - Phanerozoic and cryptozoic (Precambrian), which are delineated by the appearance of fossil remains in sedimentary rocks.

Cryptozoic is an interesting time, absolutely hidden from us, because the soft-bodied organisms that existed then left no trace in the sedimentary rocks. Periods of the geochronological scale, such as the Ediacaria and the Cambrian, appeared in the Phanerozoic through the research of paleontologists: they found in the breed a large number of various mollusks and many species of other organisms. Finding fossil fauna and flora allowed them to dismember the strata and give them the appropriate names.

Time intervals

The second largest division is an attempt to designate the historical intervals of the Earth's life when the geochronological scale was divided four main periods. The table shows them as a primary (Precambrian), secondary (Paleozoic and Mesozoic), tertiary (almost all Cenozoic) and Quaternary - a period in a special position, for although it is the shortest, but abounds with events that left bright and well-read traces.

Now for convenience, the geochronological scale of the Earth is divided into 4 eras and 11 periods. But the last two of them are divided into 7 systems (epochs). This is not surprising. Particularly interesting are the last segments, since the given geological period corresponds to the time of appearance and development of mankind.

Milestones

For four and a half billion years in the history of the Earth, the following events occurred:

• There were pre-nuclear organisms (the first prokaryotes) - four billion years ago.
• The ability of organisms to photosynthesize - three billion years ago.
• Cells with a nucleus (eukaryotes) appeared two billion years ago.
• Multicellular organisms developed - one billion years ago.
• Ancestors of insects appeared: the first arthropods, arachnids, crustaceans and other groups - 570 million years ago.
• Pisces and proto-amphibians are five hundred million years old.
• Land plants have appeared and make us happy for 475 million years.
• Insects live on land for four hundred million years, and plants in the same time interval received seeds.
• Amphibians live on the planet for 360 million years.
• Reptiles (reptiles) appeared three hundred million years ago.
• Two hundred million years ago the first mammals began to develop.
• One hundred and fifty million years ago - the first birds tried to master the sky.
• One hundred and thirty million years ago flowers blossomed (flowering plants).
• Sixty-five million years ago, the Earth forever lost dinosaurs.
• Two and a half million years ago a man (Homo genus) appeared.
• One hundred thousand years have been fulfilled since the beginning of anthropogenesis, thanks to which people have acquired their present appearance.
• Twenty-five thousand years there are no Neanderthals on Earth.

The geochronological scale and the history of the development of living organisms, fused together, albeit somewhat schematically and generically, with rather approximate datings, but the concept of the development of life on the planet provide a visual.

Rock bedding

The Earth's crust is for the most part stratified (where no faults have occurred due to earthquakes). The general geochronological scale is plotted according to the location of the strata of the rocks, which clearly show how their age decreases from the lower to the upper.

Fossilized organisms also change as they move up: they become more complex in their structure, some undergo significant changes from layer to layer. This can be observed without visiting palaeontological museums, and simply descending into the metro - on the facing granite and marble left their prints very remote from us era.

Anthropogen

The last period of the Cenozoic era is a modern stage of earthly history, including Pleistocene and Holocene. What did not happen in these turbulent millions of years (experts believe so far in different ways: from six hundred thousand to three and a half million). There were repeated changes in cooling and warming, huge continental glaciers, when the climate was moistened to the south of the glaciers, the fresh and saline water pools appeared. The glaciers absorbed a part of the World Ocean, the level in which it dropped by a hundred or more meters, due to which the continental connections were formed.

Thus, there was an exchange of fauna, for example, between Asia and North America, when a bridge was formed instead of the Bering Strait. Closer to the glaciers were settled cold-loving animals and birds: mammoths, hairy rhinoceroses, reindeers, musk oxs, arctic foxes, polar partridges. They spread to the south very far - to the Caucasus and the Crimea, to Southern Europe. In the course of the glaciers, relic forests are still preserved: pine, spruce, fir. And only in the distance from them grew deciduous forests, consisting of trees such as oak, hornbeam, maple, beech.

Pleistocene and Holocene

This is the era after the Ice Age - not yet completed and not fully lived a segment of the history of our planet, which denotes an international geochronological scale. Anthropogenic period - Holocene, is calculated from the last continental glaciation (northern Europe). It was then that the land and the World Ocean received modern outlines, as well as all the geographical zones of the modern Earth. The Holocene predecessor - the Pleistocene is the first epoch of the anthropogenic period. The cold snap on the planet has begun - the main part of this period (Pleistocene) was marked by a much colder climate than the modern one.

The northern hemisphere is experiencing the last glaciation - thirteen times the surface of the glaciers surpassed modern formations, even in interglacial intervals. Pleistocene plants are the closest to modern plants, but they were located somewhat differently during the periods of glaciation. Varieties of species and species of fauna changed, survived adapted to the Arctic life form. The southern hemisphere has not recognized such tremendous upheavals, so the plants and the animal kingdom of the Pleistocene are still present in many forms. It was in the Pleistocene that the evolution of the genus Homo took place - from Homo habilis (archanthropes) to Homo sapiens (neanthropines).

When did mountains and seas appear?

The second period of the Cenozoic era - the Neogene and its predecessor - the Paleogene, including the Pliocene and the Miocene about two million years ago, lasted about sixty-five million years. In the Neogene, the formation of almost all mountain systems has been completed: the Carpathians, the Alps, the Balkans, the Caucasus, the Atlas, the Cordillera, the Himalayas and so on. At the same time, the outlines and dimensions of all marine basins changed, as they were heavily drained. It was then that Antarctica and many mountain regions frosted.

Marine inhabitants (invertebrates) have already become close to modern species, and on land mammals - bears, cats, rhinoceroses, hyenas, giraffes, deer dominated. Anthropoid apes develop so much that a little later (in the Pliocene), Australopithecines could appear. On the continents, mammals lived apart, since there was no connection between them, but in the late Miocene Eurasia and North America the fauna nevertheless exchanged, and at the end of the Neogene from North America, the fauna migrated to the South. It was then that the tundra and the taiga formed in the northern latitudes.

Paleozoic and Mesozoic Era

Mesozoic precedes the Cenozoic era and lasted 165 million years, including the Cretaceous, Jurassic and Triassic periods. At this time, mountains were forming intensively on the peripheries of the Indian, Atlantic and Pacific oceans. Reptiles began their dominance on land, in water, and in the air. Then the first, still very primitive mammals appeared.

Paleozoic is located on the scale in front of the Mesozoic. It lasted about three hundred and fifty million years. This is the time of the most active mountain building and the most intensive evolution of all higher plants. Almost all known invertebrates and vertebrates of different types and classes were formed just then, but there were no mammals and birds yet.

Proterozoic and archaic

The Proterozoic era lasted about two billion years. At this time, processes of sedimentation were active. Well developed blue-green algae. More information about these far-off times the opportunity was not presented.

Archean is the most ancient era in the documented history of our planet. It lasted about a billion years. As a result of active volcanic activity, the very first living microorganisms appeared.