Currently, the Cenozoic era continues on Earth. This stage of the development of our planet is relatively short when compared with the previous ones, for example, the Proterozoic or Archean. While it is only 65.5 million years.

The geological processes that took place during the Cenozoic shaped the modern appearance of the oceans and continents. Gradually, the climate changed and, as a result, the flora in one or another part of the planet. The previous era - the Mesozoic - ended with the so-called chalk disaster leading to the extinction of many animal species. The beginning of a new era was marked by the fact that the empty ecological niches began to be filled again. The development of life in the Cenozoic era took place rapidly both on land and in water and in the air. The dominant position was occupied by mammals. Finally, human ancestors appeared. People turned out to be very "promising" creatures: despite repeated climate changes, they not only survived, but also evolved, settling all over the planet. With time human activity has become another factor in the transformation of the Earth.

Cenozoic era: periods

Previously, the Cenozoic (“era of new life”) was usually divided into two main periods: Tertiary and Quaternary. Now there is another classification. The very first stage of the Cenozoic is the Paleogene ("ancient formation"). It began about 65.5 million years ago and lasted 42 million years. The Paleogene is divided into three sub-periods (Paleocene, Eocene and Oligocene).

The next stage is the Neogene ("new formation"). This epoch began 23 million years ago, and its duration was approximately 21 million years. The Neogene period is divided into Miocene and Pliocene. It is important to note that the emergence of human ancestors dates back to the end of the Pliocene (although at that time they did not even resemble modern people). Somewhere 2-1.8 million years ago, the Anthropogenic, or Quaternary period began. It continues to this day. Throughout the Anthropogen, human development took place (and is happening). The sub-periods of this stage are the Pleistocene (epoch of glaciation) and Holocene (post-glacial epoch).

Climatic conditions of the Paleogene

The long period of the Paleogene opens the Cenozoic era. The climate of the Paleocene and Eocene was mild. Around the equator average temperature reached 28 °C. In the North Sea area, the temperature was not much lower (22-26 °C).

On the territory of Svalbard and Greenland, evidence was found that plants characteristic of modern subtropics felt quite comfortable there. Traces of subtropical vegetation have also been found in Antarctica. There were no glaciers or icebergs in the Eocene yet. There were areas on Earth that did not lack moisture, regions with a variable humid climate and arid regions.

During the Oligocene period, it became sharply colder. At the poles, the average temperature dropped to 5°C. The formation of glaciers began, which later formed the Antarctic Ice Sheet.

Paleogene flora

The Cenozoic era is the time of the widespread domination of angiosperms and gymnosperms (conifers). The latter grew only in high latitudes. dominated at the equator rain forests, which were based on palm trees, ficuses and various representatives of sandalwood. The farther from the sea, the drier the climate became: in the depths of the continents savannahs and woodlands spread.

In the middle latitudes, moisture-loving tropical and temperate plants (tree ferns, breadfruit, sandalwood, banana trees) were common. Closer to high latitudes, the species composition became completely different. These places are characterized by typical subtropical flora: myrtle, chestnut, laurel, cypress, oak, thuja, sequoia, araucaria. Plant life in the Cenozoic era (in particular, in the Paleogene era) flourished even beyond the Arctic Circle: in the Arctic, Northern Europe and America, the predominance of coniferous-broad-leaved deciduous forests was noted. But there were also subtropical plants listed above. The polar night was not an obstacle to their growth and development.

Paleogene fauna

The Cenozoic era provided the fauna with a unique chance. Animal world changed dramatically: dinosaurs were replaced by primitive small mammals living mainly in forests and swamps. There are fewer reptiles and amphibians. Various proboscis animals predominated, including indicotheres (similar to rhinoceroses), tapir and pig-like animals.

As a rule, many of them were adapted to spend part of the time in the water. During the Paleogene period, the ancestors of horses, various rodents, and later predators (creodonts) also appear. Toothless birds nest on the tops of trees, predatory diatryms live in the savannas - birds that cannot fly.

Great variety of insects. As for the marine fauna, the flowering of cephalopods and bivalves, corals begins; primitive crayfish, cetaceans appear. The ocean at this time belongs to bony fish.

Neogene climate

The Cenozoic era continues. The climate in the Neogene era remains relatively warm and rather humid. But the cooling, which began in the Oligocene, makes its own adjustments: the glaciers no longer melt, the humidity drops, and the continental climate intensifies. By the end of the Neogene, zoning approached modern (the same can be said about the outlines of the oceans and continents, as well as about the relief earth's surface). The Pliocene marked the beginning of another cold snap.

Neogene, Cenozoic era: plants

At the equator and tropical zones either savannas or moist forests still predominate. The temperate and high latitudes boasted the greatest diversity flora: deciduous forests, mainly evergreen, were common here. As the air drier, new species appeared, from which the modern flora of the Mediterranean gradually developed (olive, plane trees, walnut, boxwood, southern pine and cedar). In the north, evergreens no longer survived. On the other hand, coniferous-deciduous forests showed a wealth of species - from sequoia to chestnut. At the end of the Neogene, such landscape forms as taiga, tundra and forest-steppe appeared. Again, this was due to the cold. North America and Northern Eurasia became taiga regions. In temperate latitudes with an arid climate, steppes were formed. Where there used to be savannahs, semi-deserts and deserts arose.

Neogene fauna

It would seem that the Cenozoic era is not so long (in comparison with others): flora and fauna, however, have changed a lot since the beginning of the Paleogene. Placentals became the dominant mammals. At first, the anchitherian and then the hipparion fauna developed. Both are named after characteristic representatives. Anchiterium is the ancestor of the horse, a small animal with three fingers on each limb. Hipparion is, in fact, a horse, but still three-toed. There is no need to think that only relatives of horses and simply ungulates (deer, giraffes, camels, pigs) belonged to the indicated faunas. In fact, among their representatives were predators (hyenas, lions), and rodents, and even ostriches: life in the Cenozoic era was fantastically diverse.

The spread of these animals was facilitated by an increase in the area of ​​savannahs and steppes.

At the end of the Neogene, human ancestors appeared in the forests.

Anthropogenic climate

This period is characterized by alternation of glaciations and warmings. When the glaciers advanced, they lower bounds reached 40 degrees north latitude. The largest glaciers of that time were concentrated in Scandinavia, the Alps, North America, Eastern Siberia, the Subpolar and Northern Urals.

In parallel with the glaciations, the sea attacked the land, although not as powerful as in the Paleogene. Interglacial periods were different mild climate and regression (draining of the seas). Now there is just another inter glacial period, which should end no later than 1000 years. After it, another glaciation will occur, which will last about 20 thousand years. But it is not known whether this will actually happen, since human intervention in natural processes has provoked climate warming. It is time to think whether the Cenozoic era will end in a global ecological catastrophe?

Flora and fauna of Anthropogen

The onset of glaciers forced heat-loving plants to shift south. True, mountain ranges interfered with this. As a result, many species have not survived to this day. During the glaciations, there were three main types of landscapes: taiga, tundra and forest-steppe with their characteristic plants. Tropical and subtropical belts were greatly narrowed and shifted, but still remained. In the interglacial periods, broad-leaved forests dominated the Earth.

As for the fauna, the supremacy still belonged (and belongs) to mammals. Massive, woolly animals (mammoths, woolly rhinos, megaloceros) became calling card ice ages. Along with them there were bears, wolves, deer, lynxes. All animals as a result of cooling and warming were forced to migrate. The primitive and the unadapted were dying out.

Primates also continued their development. The improvement of the hunting skills of human ancestors can explain the extinction of a number of game animals: giant sloths, horses of North America, mammoths.

Results

It is not known when the Cenozoic era, the periods of which we examined above, will end. Sixty-five million years by the standards of the universe is quite a bit. However, during this time, continents, oceans and mountain ranges. Many species of plants and animals have died out or evolved under the pressure of circumstances. Mammals have taken the place of dinosaurs. And the most promising of the mammals turned out to be man, and the last period of the Cenozoic - the anthropogen - is associated mainly with the activities of people. It is possible that it depends on us how and when the Cenozoic era will end - the most dynamic and shortest of the earth's eras.

This era is subdivided into the Paleogene, Neogene and Anthropogenic periods. There was a division cenozoic era and into two periods - Tertiary and Quaternary, of which the Tertiary united the Paleogene and Neogene, and the Quaternary corresponded to the Anthropogenic period.

In the Paleogene, and especially in the Neogene, a new powerful folding and mountain building took place, which was called the Alpine era. Several phases of folding are noted, of which the most stressful occur in the Neogene. During this era, the largest mountainous countries were formed (Atlas, the Andalusian mountains, the Pyrenees, the Apennines, the Alps, the Carpathians, the mountains of the Balkan Peninsula, the mountains of Asia Minor, the Caucasus, the mountains of Iran, the Pamirs, the Himalayas, the mountains South-East Asia and the Malay Archipelago, the mountains of Kamchatka and Sakhalin, the Kor-

dealers and the Andes of North and South America). In addition, in a number of more ancient mountainous countries, already severely destroyed by this time by denudation, new powerful faults arose, uplifts and subsidence occurred (central Europe, Tien Shan, Altai, etc.). Simultaneously with mountain building, which occurred mainly in the northern hemisphere, Australia separated from Asia in the southern hemisphere, the Red Sea depression formed, deep faults cut through East Africa, large faults spread to the northern hemisphere, where the formation of the northern part of the Atlantic Ocean took place, the depression of which acquired outlines close to modern. The areas of manifestation of volcanism were close to those existing at the present time.

Mountain building, which took place along the outskirts of previously formed platforms, involved these platforms in its movement, in connection with which the outlines of the seas changed greatly. On the territory of the USSR, powerful transgressions swept the south of the Russian Plain, Central Asia, and Western Siberia.

The climate in the Paleogene (before the manifestation of intense mountain building) is warm, humid without sharp temperature fluctuations over vast areas. In the Neogene, the climate becomes more continental, with sharply defined climatic provinces, but generally remains warmer than today.

The flora of the Paleogene and Neogene, which was dominated by angiosperms, is very similar to the vegetation of modern tropical and subtropical latitudes, and these plant species spread in the Paleogene up to the northern islands of Europe and North America. In the Neogene, the area of ​​moisture-loving forests was greatly reduced, and drought-resistant flora and steppe spaces appeared in temperate latitudes.

The fauna of the Paleogene and Neogene is rich and diverse. On land, various mammals and birds dominate. Marine fauna becomes very close to modern; marine mammals appear. In the Neogene, with the appearance of steppe spaces, ungulates (antelopes, horses, etc.) quickly begin to evolve. At the same time, the development of humanoids takes place. In the Neogene deposits of the island of Java, the remains of an ape-man (pithecanthropus) were found, and in China - a man (sinatrop), who used stone tools and fire.

The deposits of the Paleogene and Neogene are rich in various minerals, among which deposits of oil, gas and coal are of great importance.

Climate change, which began in the Neogene, led at the beginning of the Anthropogenic (Quaternary) period to a significant cooling, as a result of which, first in the mountains, and then on the plains, powerful glaciation develops. In the Anthropogenic period, these glaciers either grew strongly or sharply reduced to approximately modern sizes. In this regard, it is customary to single out epochs of glaciation and epochs of interglacials. For Eastern European

plains, most researchers indicate four glaciations: Oka, Dnieper, Moscow and Valdai. The boundaries of the two glaciations are shown in Fig. 28.

Significant climate change has greatly affected the composition of flora and fauna. During the Anthropogenic period, polar and temperate

latitudes are inhabited by animals and plants adapted to the harsh climatic conditions. Instead of the heat-loving flora of the Neogene, forests of the taiga type develop here, and later tundra flora also appears.

During this period, the duration of which is relatively short (1 000 000 years), there were no major changes in the outlines of the seas and continents. Small transgressions and regressions of the sea occurred in the coastal strip of the World Ocean in the interglacial and postglacial periods. The sizes of closed basins (Caspian Sea) changed more significantly. In this regard, deposits of marine origin in the area of ​​modern continents are very limited in distribution. Continental deposits (glacial, river, lacustrine, marsh, etc.) are more widespread.

After the intense manifestation of mountain building that occurred in the Neogene, the movements of the earth's crust in the Anthropogenic period did not stop and continue to the present, as evidenced by strong earthquakes, volcanism, uplift and subsidence of large blocks of the earth's crust occurring in the zones of Alpine folding. All these processes, together with the activity of external geological agents, affect the ancient relief of the lithosphere and are reflected in its modern relief.

On the whole, the Cenozoic era has now been marked by very important events. 1. A new thing happened - Alpine mountain building (see Fig. 27), mountain structures rose, which are currently the highest mountains of the Earth. 2. Mountainous countries that arose in the Paleozoic and mesozoic era. By the beginning of the Cenozoic, they were badly destroyed. In the era of Alpine folding, they experienced repeated movements, were broken by faults, raised to great height and again turned into mountainous countries with sharp landforms. 3. There was a further reduction of geosynclines and platforms grew due to them. 4. The uplift of young mountain ranges was accompanied by the uplift of adjacent platform sections, which affected the distribution of land and sea. This was also influenced by the faults of the earth's crust, which separated the continents. 5. As a result of volcanism, vast lava plateaus and plains were formed, high volcanic mountains and highlands arose, new mineral deposits were formed in the bowels of the Earth (at present still hidden under a thick sedimentary cover). 6. The climate has changed a lot. From warm and monotonous, characteristic of the beginning of the Cenozoic era, it became sharp, with a large number of climatic zones and provinces. 7. Large glaciers arose, repeatedly spreading over vast expanses of land. 8. The animal and plant world have taken on their modern look. 9. A man appeared and began his activity.

Finishing a brief description of the geological history of the Earth, its complexity should be noted. Without touching on the development of the organic world, let us turn to the development of the lithosphere and its relief, taking the territory of the USSR as an example.

Back to top Paleozoic era within this territory there were two rigid masses of the earth's crust: the Russian and Siberian platforms with their most rigid parts, shields. As a result of repeated epochs of folding and mountain building, the pliable zones (geosynclinal belts) located between these platforms, filled with thick strata of sediments, were crushed into folds and turned into mountain structures, attached to the outskirts of the platforms or connecting the platforms to each other. This process is clearly traced in the history of the Ural-Tyan-Shan geosyncline. At the beginning of the Paleozoic era, thick layers of sediments accumulated near the southern margin of the Siberian platform.

and mountain building took place (the Caledonian era of folding), as a result of which mountains arose in the area of ​​\u200b\u200bthe modern Baikal region, in the Sayans, in Altai. For the rest of the geosynclinal belt, this epoch was expressed as a preliminary one, since the mountains that arose here quickly collapsed and were again largely flooded by the sea (Kazakhstan, Western Altai, etc.). On the outskirts of the mountainous countries that had arisen, in actively sagging areas of the geosyncline that had not yet closed, the accumulation of new sediment layers continued, culminating in a new folding and mountain building that developed at the end of the Paleozoic era (the Hercynian epoch). Vast mountainous countries were formed: the Urals, Tien Shan, the Kazakh mountainous country and mountains in the place of a significant part of the West Siberian lowland. The subsequent history of these mountainous countries is different. Most of them were destroyed by denudation agents, experienced subsidence and are currently under a thick layer of Meso-Cenozoic deposits that make up the sedimentary cover of the West Siberian Lowland. The outlying western part, which has experienced minor uplifts as a result of recent movements, stretches along the edge of the Russian Platform in the form of the low Ural Mountains. Significant expanses of ancient mountain country, strongly destroyed by denudation agents, which did not experience significant uplifts and subsidence, are observed in Central Kazakhstan. The southernmost parts of the ancient mountainous country, once already destroyed to the state of small hills and later under the influence of powerful mountain-building movements of the Alpine folding era, were broken into blocks and raised to a great height, which led to the formation of the mountainous terrain of the Tien Shan.

The above example indicates that the earth's crust, developing along general plan from a pliable geosyncline, through a mountain structure to a rigid platform with a flat relief. achieves this in different parts in different ways. These paths are often clearly reflected in the relief and can explain its diversity.

GEOLOGICAL MAP AND PROFILES General information about geological maps

Among the maps reflecting natural phenomena, one of the first places is occupied by geological maps created as a result of geological surveys. A geological map gives an idea of ​​the geological structure of a section of the earth's surface and is essentially a vertical projection of bedrock outcrops plotted on a topographic base of a certain scale. Such a map is called a geological map proper, since its construction is based on the principle of separating strata rocks, different in age.

The geological map is the basis for all other maps compiled in the course of complex geological mapping. The latter provides for the compilation of a series of maps that highlight certain aspects of the geological structure of the area. The noted complex of maps includes: lithological-petrographic, structural-tectonic, hydrogeological, facies-paleogeographic, geomorphological, engineering-geological, various geophysical, minerals.

Depending on the scale, all geological maps are divided into overview, regional medium-scale and large-scale.

Overview maps highlight the structure of individual continents and states. The largest scale is 1:1,000,000. The topographic base has been simplified.

Regional maps (small-scale) - display a section of the earth's surface, characterized by the unity of the geological structure (the Caucasus, the Urals, the Donbass, etc.). Map scale from 1:1,000,000 to 1:200,000. The topographic base has been simplified.

Medium-scale - display in detail the geology of a relatively small area. Their scale is from 1:200,000 to 1:25,000. The topographic base is simplified.

Large-scale geological maps - compiled for mineral deposits. The scales are from 1:1000 to 1:500. The topographic base is often compiled on purpose.

Geological work in the field usually begins with reconnaissance routes, which make it possible to get a general idea of ​​the area and identify the features of its individual parts. After the reconnaissance, the plan of field work and research is specified, time is allocated, and the order of routes is outlined. In this case, the degree of exposure of the area is of great importance, which can be judged with a sufficient degree of reliability from aerial photographs.

The most complete are subjected to priority research - supporting outcrops (sections) or wells with continuous core sampling (rock samples obtained from wells during drilling). Intermediate outcrops, in which only parts of the main section are exposed, are studied later.

Simultaneously with the description of natural and artificial sections, the vertical and planned binding of the marking (reference) layers and horizons identified in them, which are important for mutual coordination, is carried out. Depending on the scale of the shooting, the binding can be instrumental or visual. When describing the stratigraphic sequence of layers in sections, their thickness and occurrence elements must be measured. As a result, a summary section (column) is compiled.

Comparison of sections and tracking of identified stratigraphic units over the entire area of ​​the region makes it possible to

get an idea of ​​their structure (forms of occurrence) and facies changes. Binding the outcrops of these layers to the earth's surface makes it possible to draw the contours of the age boundaries of bedrock (pre-Quaternary) rocks on a topographic map - to create a geological map.

Proper geological maps

The methodology for compiling a geological map depends on the scale of the survey, exposure, and mainly on the geological structure of the area. With horizontal, inclined and folded occurrence of layers, it is different.

Horizontal occurrence is characterized by a close value of the absolute height marks of the roof or bottom of the layer. Depending on the depth of the dissection of the mapped area, with a horizontal occurrence on the surface, either only the upper layer (with a shallow dissection) or deeper layers (with a deep dissection) will be exposed. The horizontal occurrence of the layers is easily determined by the coincidence or almost parallel arrangement of the outlets of the mapped layer and the contours of the topographic base (Fig. 29).

If the layers are removed from their original horizontal position and have acquired a slope in one direction, then their occurrence is called monoclinal (one-slope). To determine the position of monoclinal layers in space, the method of finding the lines of strike and dip of layers is used. A straight line, which is obtained by crossing a monoclinal layer with a horizontal plane, is called the strike line (Fig. 30). Perpendicular to the strike line there is a dip line directed towards the greatest slope of the layer. The determination of the occurrence elements, the orientation of the lines of strike and fall according to the cardinal points is carried out using a mountain compass.

As mentioned above, in case of horizontal occurrence, the lines of layer outputs will coincide with the contour lines of the topographic map or be located parallel to them. With a vertical occurrence, the terrain will not affect the configuration of the lines of intersection of the layer by the plane, since in this case all stretch lines are projected onto the plane in one line, which will be straight with a straight vertical layer and curved with a curved vertical surface.

In addition to the above two extreme cases of the image on the plane of projections of horizontally and vertically lying layers, there can be countless variants of projections of obliquely lying layers, and their configuration will be directly dependent on the angle of incidence and the terrain. With a highly dissected relief and a gentle dip of the layers, the outcrop of the reservoir will have a more complex contour than with a steep bedding and weak

bohm dismemberment of the relief. The dip direction of inclined layers on geological maps is determined by their age sequence. The slope will always be towards the location of younger deposits (Fig. 31).

The folded forms of the occurrence of the layers significantly conditional / bend the pattern of the geological map. The exits of the selected age subdivisions are located in stripes, closed rounded or elliptical contours. Layers of the same age within the fold are always arranged symmetrically with respect to the central (axial) part of the fold, which does not have a paired exit. When reading geological maps depicting a folded structure, it is first necessary to determine the age relationships of the layers in order to establish the position of symmetrically located bands of ancient and young layers with respect to the central unpaired band. The position of the latter determines the presence of the axial part of the anticline or syncline. In the core of the anticline, older layers always outcrop, bordered by outcrops of layers of younger deposits. In the core of the syncline, on the contrary, younger layers lie surrounded by older ones (Fig. 32).

Tectonic disturbances on a geological map are represented by lines that break geological boundaries. The image of displacements of age boundaries in the plan and the configuration of the lines of discontinuities depend on the type of structure, the angles of incidence of the layers, the angle of inclination of the ejector, and other factors.

In the geological mapping of igneous rocks, the relationship of the latter with the enclosing strata is taken into account. Mutually

intrusion ratios are presented differently when studying intrusive rocks that have intruded into the sedimentary strata of the earth's crust and are exposed as a result of denudation processes and igneous rocks formed on the earth's surface as a result of volcanic processes. On geological maps, the contour of the outcrop of igneous bodies is depicted and their age and geological composition are indicated with the help of indices.

When compiling geological maps, the established symbols of three types are used: color; indices (alphabetic and digital); dashed.

Color symbols determine the age of rocks, and when depicting outcrops of intrusions, their composition. Indices - determine the age of the distinguished units and sometimes their origin (intrusion and effusion indices). Stroke symbols can replace color symbols or, when applied to a color background, indicate the composition of rocks. Standards for color symbols for subdivision of the geochronological scale were proposed by the Russian geologist A.P. Karpinsky and approved in 1881 by the II International Geological Congress.

In the geochronological scale, two types of subdivisions are used. Some correspond to the period of time of the selected subdivision, others are thicker than the rocks formed at that time. Accordingly, an era is parallelized with a group, a period with a system, an epoch with a department, a century with a tier, and time with a zone.

Color designation standards are adopted for period systems.

Anthropogenic period, system - light gray color

Neogene » » -yellow

Paleogene » » -orange

Cretaceous » » - green

Jurassic » » -blue

Triassic » » -violet

Perm » » -brown-red

Coal » » - gray

Devon » » -brown

Silurian "" - light olive

Ordovician » » - olive dark

Cambrian » » - pink

Outcrops of Archean (AR) and Proterozoic (PR) rocks are indicated by various shades of red (large-scale maps of areas of the indicated age are colored with colors and strokes adopted for igneous rocks and formations). More subdivisions of the geochronological scale (departments, stages, etc.) are painted over with tones of the main color of the period (system), and the density of the tone weakens from ancient subdivisions to young ones.

When compiling a geological map on a scale larger than 1: 100,000, the standard color scale may not be enough. In this case, symbols are added in the form of specks, stripes and others, but in the colors adopted for given period(systems).

Igneous rocks are indicated by bright colors with indices corresponding to the name of the rocks. Acid and intermediate rocks are indicated in red, alkaline in orange, basic rocks in green, and ultrabasic rocks in purple.

Effusive rocks on the maps of the old edition were indicated by different colors with indices put down in accordance with the composition of the rocks. Acid effusives were colored orange, basic ones - green. On the maps of the latest editions, effusives are painted over with a color showing their age, with the addition of indices and strokes that determine the composition of the rocks.

The system (period) index is used as the basis for the alphabetic and numerical designation of sedimentary, igneous and metamorphic rocks in the geochronological scale and on the geological map. When designating a department, a number is added to it, corresponding to the lower, middle, upper departments (epochs), or when divided into two parts - lower and upper. When subdividing a department (epoch) into tiers (centuries), letter designations are added to the index of the department (epoch), consisting of the first letter of the tier name and the first consonant letter in this name. The above can be illustrated by the example of the index of the Cretaceous system (period): the index of the system (period) - (K), the indices of departments (epochs) - (K 1) and (K 2), the index of one of the tiers (ages) - Valanginian - TO 1 v. Parts

tiers are indicated in Arabic numerals, put down at the bottom right of the index - TO 1 v 1 .

On detailed geological maps at the top right, above the index of the period (system), sometimes indices are affixed indicating the facies composition of the rocks: T- marine sediments, J- lake, h- coal-bearing, f- flash *.

In addition to age groups, it often becomes necessary to single out local subdivisions that correspond to certain stages of the geological development of a given area. In this case, the rocks are divided into series, suites, subsuites, and horizons. Where possible, local divisions are linked to a generally accepted age scale. Indices of local divisions are formed from two lowercase Latin letters (the first letter of the name and the nearest consonant). Letters are written to the right of the group, system or department index. For example: J 1 bg- Lower Jurassic section, Bezhitinskaya suite.

For a division covering two adjacent departments or systems, the index is formed by connecting them with a + (plus) sign or a dash - (hyphen). The + sign is put if two neighboring subdivisions are combined, represented in their full development J + K; dash (hyphen) is used in all other cases. The J-K index indicates the presence of the contact between the Cretaceous and the Jurassic in the selected subdivision without determining their more accurate age boundaries.

On geological maps, in the case of replacing color designations with dashed ones, the latter are chosen arbitrarily. When depicting the composition of rocks, dashed symbols have a certain standard.

A geological section is an image of the sequence of stratification and the structure of the layers of the surface parts of the earth's crust in a vertical section. When constructing a section with any occurrence of layers, its horizontal scale must correspond to the scale of the map. The choice of vertical scale depends on the thickness of the layers. The thinnest layer in the chosen scale should not be less than 1 mm. Ideally, the value of the vertical scale should be equal to the horizontal scale. In this case, there will be no distortion in the angles of incidence and powers on the profile.

In case of inclined and folded occurrence of layers, it is necessary to take into account the direction of the profile section in relation to the strike line of inclined and folded layers; in order to eliminate the distortion of angles, a correction calculated according to special tables must be introduced.

With a horizontal occurrence of layers, the most complete section will be the line of which passes through the highest and lowest points of the relief. To build a section with a horizontal occurrence

* Flysch - powerful monotonous and rhythmic sedimentary strata of shallow marine sediments.

layers on the geological map, the places of intersection of geological boundaries with the profile line on the map should be transferred to the terrain profile and connect the obtained points with horizontal lines.

When constructing a geological section with an inclined occurrence of layers, it must be remembered that a section built in the direction of dip, with equivalent vertical and horizontal scales, will always have the true angle of inclination of the layers and thickness. In the case when the cut passes in the direction of strike, the layers have a horizontal position.

When constructing a profile section on a geological map that reflects the folded occurrence of layers, as well as with horizontal and inclined occurrence, first of all, a topographic profile is built on the scale adopted for vertical constructions. Outcrops of geological boundaries and dip angles on the wings of folds are applied to the topographic profile. Then the geological section is drawn taking into account the position of the axial surfaces of the folds in the plan.

Compilation of profile sections crossing the territory with outcrops of secant intrusions requires solving problems that are not considered in the program of this book. In the general case, when a section passes through an intrusion, it should be shown as a body that interrupts the bedding of layers in the same way as in case of discontinuities.

Engineering geological maps

Engineering-geological maps reflect the engineering-geological conditions of the territory being mapped and provide a comprehensive natural assessment necessary for construction. The task of engineering geology is to determine the geological features of the study area in order to establish its suitability for the construction and operation of engineering structures.

The geological structure has an impact on the choice of location, layout, construction of the structure and on the methods of construction work.

The engineering-geological map, together with profile sections, stratigraphic columns and comprehensive characteristics of soils, is the main document obtained as a result of engineering-geological surveys. Among engineering-geological maps for various purposes, general survey, special survey, schematic and detailed maps are usually distinguished. General overview maps serve to design various types of construction and are compiled on a small scale (1: 200,000 and smaller). The remaining categories of carts are used to design a specific type of engineering structures and are drawn up on a scale that meets the requirements of construction.

When engineering and geological surveys and mapping, the nature of the relief, the geological structure must be taken into account.

tur, composition of rocks, hydrogeological conditions and dynamics of modern processes. Terrain information is needed to select a construction site, estimate the amount of earthworks, lay access roads and other design data. The geological structure gives an idea of ​​the occurrence of bedrocks and the position of their roof in relation to the modern hydrographic network. The composition of the rocks (ground conditions) is subject to particularly careful study and is depicted on the map in accordance with the established geological and petrographic classification.

The study of water content is essential. On the maps, conventional signs indicate the depth of groundwater, water abundance, pressure, chemical characterization. In some cases (on large-scale maps), the groundwater surface is depicted as isolines. The dynamics of modern geological processes is reflected on large-scale maps by conventional signs and boundaries that outline areas where certain processes develop (landslides, karst, permafrost, subsidence of rocks, various forms of erosion, etc.). The qualitative and quantitative assessment of dynamic processes is noted on the maps, the intensity of the development of the process is indicated.

When drawing up an engineering-geological map, it is essential to select colors and symbols that determine its visibility and ease of reading.

Tectonic maps

Tectonic maps depict structural elements of various scales, categories and ages.

The compilation of tectonic maps is one of the most important and active methods of studying and analyzing the development of the structures of the earth's crust. Depending on the size of the territory for which the map is being compiled, the scale and symbols, it is customary to distinguish between general (summary) and regional tectonic maps. In addition, so-called structural maps are compiled to display the morphology of tectonic structures. On general tectonic maps, structural elements of a large scale are depicted, which are the main structures of the earth's crust. The symbols (legend) used in the preparation of such maps are common to the entire surface of the Earth and can be used in any of its regions. Regional maps reflect the structure of a particular section of the earth's crust; the symbols adopted for it may be of little use for their use when drawing up a map of another area.

The relief of the surface of a particular structure depicted on a tectonic map is transmitted using isolines (horizontals) connecting points with an equal value of occurrence marks, calculated from the level of the World Ocean.

The starting point for general tectonic mapping is to establish the age of folding of the main structures,

the time of formation of the geosyncline, i.e. in time

graduation geosynclinal and the beginning of the platform stages of development of the study area. The moment of transformation of the geosynclinal folded system into a platform is a natural boundary in the development of the earth's crust.

Within Europe and neighboring parts of other continents, territories are distinguished that have survived the following main epochs of folding, the age of which is determined by the time of completion of the geosynclinal stage of development: Precambrian (Archaean and Proterozoic), Baikal, Caledonian, Hercynian and Alpine. Larger subdivisions (cycles) in the development of the earth's crust, uniting many eras and periods (stages) of folding, are called megachrons. In the history of the formation of the earth's crust, several megachrons can be distinguished, but the most studied is the last one, called neogey. In this new, last, megachron, a radical restructuring of the earth's crust and the formation of its modern structure took place. The age of these structures is reflected on tectonic maps by special indices and colors.

On the tectonic maps of the territory of the USSR for the Baikal folding (Proterozoic) is accepted Blue colour, for the Caledonian - lilac, for the Hercynian (Varisian) - brown, for the Alpine - yellow. Older megachrons are depicted in shades of red.

When depicting various zones of geosynclinal regions - eugeosynclines and miogeosynclines, shades of colors are used that determine the age of a particular folded structure and an alphabetic index is put. For example, the eugeosyn-clinal zone of the Caledonian folding is designated by the index - еС. Structural floors in folded structures are also distinguished by the density of tone of the accepted age coloration, and the lower structural floors are painted over with a more intense shade. Letter indices are supplemented with numbers. K 1, for example, denotes the lower floor of the Karelian folding (Proterozoic), C 2 - the middle floor of the Caledonian folding, A 3 - the upper structural floor of the Alpine folding, etc. There are alphabetic and numeric designations for more fractional divisions - subfloors. For example, A 2 1 is the upper sublevel of the lower structural level of Alpine folding.

The marginal troughs are indicated by a striped horizontal color of the color of the upper structural level of a given folding. In the case of overlapping the marginal deflection with a platform cover, translucent shading is used under the paint of the platform cover. Internal intermountain depressions, developing simultaneously with the marginal foredeeps, are indicated by the color of the upper structural stage with molasse specks *. Fill in the middle arrays

*Molasses are clastic rocks that fill deep troughs of geosyn-clinal zones V major eras of mountain building.

are colored by folding, which turned them into rigid blocks (for example, Hercynian massifs among the structures of Alpine folding in the Caucasus, etc.).

With the introduction of general tectonic maps of the designations of eu- and miogeosynclines, structural levels and internal depressions into the legend, with appropriate detail of the contours, these maps raise their accuracy to the level of regional maps.

Within platform structures, on general tectonic maps, areas of outcrops of a folded basement (shields) and slabs, on the area of ​​which the basement is covered by a sedimentary cover, are distinguished. On shields and exposed anteclise vaults, the folded foundation is subdivided according to the epochs of folding with the allocation of structural floors. On the territory of the slabs, the surface of the folded foundation is depicted using isohypses and stepped coloring, shading the areas of subsidence and uplifts. (The submerged areas are lighter than the uplifted ones.) The age of the platforms is emphasized on tectonic maps in a certain color, which differs from the folded areas in a paler tone. To designate the sedimentary cover of the platforms, the following color tones are adopted: the sedimentary cover of the ancient platforms is indicated by a brownish-pink color, the Epicaledonian - violet-green, the Hercynian - brownish-gray.

Outcrops of intrusive massifs are depicted in the same way as on geological maps, within their modern erosional cut. The division of intrusions is made according to their belonging to certain stages of tectogenesis (early orogenic, late orogenic and anorogenic). The age of the intrusions is indicated by indexes, the composition - by color and icons adopted for geological maps.

Large discontinuities are depicted on general tectonic maps by solid and dashed red lines. In addition, tectonic maps show zones of intensive development of metamorphism and centers of modern and ancient volcanism.

Conventional signs have been worked out in great detail to designate folded and discontinuous faults displayed on tectonic maps, as well as to designate boundaries and lines separating structures of various orders and ages.

And the Paleogene, when the second largest catastrophic extinction of species occurred on Earth. The Cenozoic era is significant for the development of mammals that replaced dinosaurs and other reptiles, which almost completely died out at the turn of these eras. In the process of development of mammals, a genus of primates stood out, from which, according to Darwin's theory, humans later arose. "Cenozoic" is translated from Greek as "New Life".

Geography and climate of the Cenozoic period

During the Cenozoic era, the geographic outlines of the continents acquired the form that exists today. The North American continent moved further and further away from the remaining Laurasian, and now the Eurasian part of the global northern continent, and the South American segment moved further and further away from the African segment of southern Gondwana. Australia and Antarctica retreated more and more to the south, while the Indian segment was more and more “squeezed out” to the north, until, finally, it joined the South Asian part of the future Eurasia, causing the rise of the Caucasian mainland, and also largely contributing to the rise from water and the rest of the current part of the European continent.

The climate of the Cenozoic era gradually became more severe. The cooling was not absolutely sharp, but still not all groups of animals and plant species got used to it. It was during the Cenozoic that the upper and southern ice caps were formed in the region of the poles, and the climatic map of the earth acquired the zonation that we have today. It is a pronounced equatorial belt along the earth's equator, and further in order of distance to the poles - subequatorial, tropical, subtropical, temperate, and beyond the polar circles, respectively, the arctic and antarctic climatic zones.

Let's take a closer look at the periods of the Cenozoic era.

Paleogene

Throughout almost the entire Paleogene period of the Cenozoic era, the climate was warm and humid, although a constant trend towards cooling was traced throughout it. The average temperature in the North Sea area was kept within 22-26°C. But by the end of the Paleogene, it began to get colder and sharper, and at the turn of the Neogene, the northern and southern ice caps were already formed. And if in the case of the northern sea these were separate areas of alternately forming and melting wandering ice, then in the case of Antarctica, a persistent ice sheet began to form here, which still exists today. The average annual temperature in the region of the current polar circles dropped to 5°C.

But until the first frosts hit the poles, renewed life both in the sea and ocean depths and on the continents flourished. Due to the extinction of dinosaurs, mammals completely populated all continental spaces.

During the first two Paleogene divisions, mammals diverged and evolved into many different forms. Many different proboscis animals arose, indicothere (rhino), tapir and pig-like. Most of them were chained to some kind of water bodies, but many species of rodents also appeared, which also felt excellent in the depths of the continents. Some of them gave rise to the first ancestors of horses and other one and artiodactyls. The first predators (creodonts) began to appear. New species of birds arose, and vast areas of the savannas were inhabited by diatryms - a variety of flightless bird varieties.

Insects multiplied unusually. In the seas, cephalopods and bivalves. Corals grew very strongly, new varieties of crustaceans appeared, but bony fish received the greatest flourishing.

The most widespread in the Paleogene were such plants of the Cenozoic era as tree-like ferns, various sandalwood, banana and breadfruit trees. Closer to the equator, chestnut, laurel, oak, sequoia, araucaria, cypress, and myrtle trees grew. In the first period of the Cenozoic, dense vegetation was also widespread far beyond the polar circles. These were mostly mixed forests, but coniferous and deciduous broad-leaved plants prevailed here, the prosperity of which was absolutely no obstacle to the polar nights.

Neogene

At the initial stage of the Neogene, the climate still remained relatively warm, but a slow trend towards cooling still persisted. The ice heaps of the northern seas began to melt more and more slowly, until the upper northern shield also began to form.

The climate, due to cooling, began to acquire an increasingly pronounced continental color. It was during this period of the Cenozoic era that the continents became most similar to modern ones. South America merged with North America, and just at that time, climatic zoning acquired similar features to modern ones. By the end of the Neogene in the Pliocene Earth the second wave of sharp cooling hit.

Despite the fact that the Neogene was two times shorter than the Paleogene, it was he who was marked by explosive evolution among mammals. It was placental varieties that dominated everywhere. The main mass of mammals was divided into anchitheria, the ancestors of horse-like and hipparion, also horse-like and three-toed, but gave rise to hyenas, lions and other modern predators. All kinds of rodents were diverse at that time of the Cenozoic era, the first distinct ostrich-like ones began to appear.

In connection with the cooling and the fact that the climate began to acquire an increasingly continental color, areas of ancient steppes, savannahs and light forests were expanding, where in large quantities the ancestors of modern bison, giraffe-like, deer-like, pigs and other mammals grazed, which were constantly hunted by ancient Cenozoic predators. It was at the end of the Neogene that the first ancestors of humanoid primates began to appear in the forests.

Despite the winters of the polar latitudes, tropical vegetation was still rampant in the equatorial belt of the earth. The broad-leaved woody plants. Consisting of them, as a rule, evergreen forests interspersed and bordered on savannas and shrubs of other woodlands, subsequently it was they who gave diversity to the modern Mediterranean flora, namely olive, plane trees, walnuts, boxwood, southern pine and cedar.

were varied and northern forests. There were no evergreens here, but in the majority chestnut, sequoia and other coniferous-broad-leaved and deciduous trees grew and took root. Later, in connection with the second sharp cooling, vast areas of tundra and forest-steppes formed in the north. The tundra filled all the zones with the current temperate climate, and the places where until recently rainforests turned into deserts and semi-deserts.

Anthropogene (Quaternary period)

In the Anthropogenic period, unexpected warmings alternated with equally sharp cold snaps. The boundaries of the glacial zone of the Anthropogen sometimes reached 40° northern latitudes. Under the northern ice cap were North America, Europe up to the Alps, the Scandinavian Peninsula, the Northern Urals, Eastern Siberia.

Also, in connection with glaciation and the melting of ice caps, there was either a decline or a re-advance of the sea to land. The periods between glaciations were accompanied by marine regression and a mild climate.

On this moment there is one of these intervals, which should be replaced no later than in the next 1000 years by the next stage of icing. It will last approximately 20 thousand years, until it is again replaced by another period of warming. Here it is worth noting that the alternation of intervals can occur much faster, or it can be completely disturbed due to human intervention in earthly natural processes. It is likely that the Cenozoic era could be ended by a global ecological catastrophe similar to the one that caused the death of many species in the Permian and Cretaceous periods.

Animals of the Cenozoic era during the Anthropogenic period, together with vegetation, were pushed southward by alternately advancing ice from the north. The main role still belonged to mammals, which showed truly miracles of adaptability. With the onset of cold weather, massive woolly animals appeared, such as mammoths, megaloceros, rhinos, etc. All kinds of bears, wolves, deer, lynxes also bred strongly. Due to alternating waves of cooling and warming, animals were forced to constantly migrate. extinct great amount species that did not have time to adapt to the onset of cooling.

Against the background of these processes of the Cenozoic era, humanoid primates also developed. They increasingly improved their skills in the possession of all kinds of useful objects and tools. At some point, they began to use these tools for hunting purposes, that is, for the first time, tools of labor acquired the status of weapons. And from now on various types Animals are in real danger of extinction. And many animals, such as mammoths, giant sloths, North American horses, which were considered by primitive people to be commercial, were completely destroyed.

In the zone of alternating glaciations, the tundra and taiga regions alternated with forest-steppe, and tropical and subtropical forests were strongly pushed to the south, but despite this, most plant species survived and adapted to modern conditions. The dominant forests between periods of icing were broad-leaved and coniferous.

At the present moment of the Cenozoic era, man reigns everywhere on the planet. He randomly interferes in all sorts of earthly and natural processes. Behind last century A huge amount of substances was released into the earth's atmosphere, contributing to the formation of the greenhouse effect and, as a result, faster warming. It is worth noting that the more rapid melting of ice and the rise in the level of the world ocean contributes to the disruption of the general picture of the climatic development of the earth.

Due to upcoming changes, undercurrents may be disrupted, and, as a result, the general planetary intra-atmospheric heat exchange, which may lead to even more massive icing of the planet following the warming that has begun at the moment. It is becoming more and more clear that how long the Cenozoic era will be, and how it will eventually end, will now depend not on natural and other natural forces, but on the depth and arrogance of human intervention in global natural processes.


The periods of the geological history of the Earth are the epochs, the successive change of which formed it as a planet. At this time, mountains formed and collapsed, seas appeared and dried up, ice ages succeeded each other, and the evolution of the animal world took place. The study of the geological history of the Earth is carried out on sections of rocks that have preserved mineral composition the period that formed them.

Cenozoic period

The current period of the geological history of the Earth is the Cenozoic. It began sixty-six million years ago and continues to go on. The conditional boundary was drawn by geologists at the end Cretaceous when there was a mass extinction of species.

The term was proposed by the English geologist Phillips in the middle of the nineteenth century. Its literal translation sounds like " new life". The era is divided into three periods, each of which, in turn, is divided into eras.

Geological periods

Any geological era divided into periods. IN Cenozoic era distinguish three periods:

Paleogene;

Quaternary period of the Cenozoic era, or anthropogen.

In earlier terminology, the first two periods were combined under the name "Tertiary period".

On land, which had not yet had time to finally divide into separate continents, mammals reigned. There were rodents and insectivores, early primates. In the seas the reptiles have been replaced predatory fish and sharks, new species of mollusks and algae appeared. Thirty-eight million years ago, the diversity of species on Earth was amazing, the evolutionary process affected representatives of all kingdoms.

Only five million years ago, the first great apes began to walk on land. Three million years later, on the territory belonging to modern Africa, Homo erectus began to gather in tribes, collect roots and mushrooms. Ten thousand years ago appeared modern man who began to reshape the Earth to suit his needs.

Paleography

The Paleogene lasted forty-three million years. The continents in their modern form were still part of Gondwana, which was beginning to split into separate fragments. South America was the first to go into free swimming, becoming a reservoir for unique plants and animals. In the Eocene era, the continents gradually occupy their present position. Antarctica is separating from South America and India is moving closer to Asia. An array of water appeared between North America and Eurasia.

In the Oligocene era, the climate becomes cool, India finally consolidates below the equator, and Australia drifts between Asia and Antarctica, moving away from both. Due to temperature change in south pole ice caps are formed, which leads to a decrease in sea level.

In the Neogene period, the continents begin to collide with each other. Africa "rams" Europe, as a result of which the Alps appear, India and Asia form the Himalayan mountains. In the same way, the Andes and rocky mountains appear. In the Pliocene era, the world becomes even colder, forests die out, giving way to steppes.

Two million years ago, a period of glaciation sets in, sea levels fluctuate, white caps at the poles either rise or melt again. The animal and plant world is being tested. Today, humanity is experiencing one of the stages of warming, but on a global scale, the ice age continues to last.

Life in the Cenozoic

The Cenozoic periods cover a relatively short period of time. If you put the entire geological history of the earth on the dial, then the last two minutes will be allotted for the Cenozoic.

The extinction event that marked the end of the Cretaceous and the beginning new era, erased from the face of the Earth all animals that were larger than a crocodile. Those who managed to survive were able to adapt to new conditions or evolved. The drift of the continents continued until the appearance of people, and on those of them that were isolated, a unique animal and plant world could be preserved.

The Cenozoic era was distinguished by a large species diversity of flora and fauna. It is called the time of mammals and angiosperms. In addition, this era can be called the era of the steppes, savannahs, insects and flowering plants. Crown evolutionary process on Earth can be considered the appearance of Homo sapiens.

Quaternary period

Modern humanity lives in the Quaternary era of the Cenozoic era. It began two and a half million years ago, when in Africa great primates began to stray into tribes and get their own food by gathering berries and digging up roots.

The Quaternary period was marked by the formation of mountains and seas, the movement of continents. The earth has acquired the form it has now. For geologists, this period is just a stumbling block, since its duration is so short that the methods of radioisotope scanning of rocks are simply not sensitive enough and give out large errors.

The characteristic of the Quaternary period is made up of materials obtained by radiocarbon analysis. This method is based on measuring the amount of rapidly decaying isotopes in soil and rocks, as well as bones and tissues of extinct animals. The entire period of time can be divided into two epochs: Pleistocene and Holocene. Humanity is now in the second age. While there are no exact calculations when it will end, but scientists continue to build hypotheses.

Pleistocene Epoch

The Quaternary period opens the Pleistocene. It began two and a half million years ago and ended only twelve thousand years ago. It was ice age. Long ice ages were interspersed with short warming periods.

One hundred thousand years ago in the area of ​​modern Northern Europe a thick ice cap appeared, which began to spread in different directions, absorbing more and more new territories. Animals and plants were forced to either adapt to new conditions or die. The frozen desert stretches from Asia to North America. In some places, the thickness of the ice reached two kilometers.

The beginning of the Quaternary period turned out to be too harsh for the creatures that inhabited the earth. They are used to warm, temperate climates. In addition, ancient people began to hunt animals, who had already invented the stone ax and other hand tools. Entire species of mammals, birds and representatives of marine fauna are disappearing from the face of the Earth. Could not stand the harsh conditions and the Neanderthal. Cro-Magnons were more hardy, more successful in hunting, and it was their genetic material that had to survive.

Holocene epoch

The second half of the Quaternary period began twelve thousand years ago and continues to this day. It is characterized by relative warming and climate stabilization. The beginning of the era was marked by the mass extinction of animals, and it continued with the development of human civilization, its technical flourishing.

Changes in the animal and plant composition throughout the epoch were insignificant. Mammoths finally died out, some species of birds ceased to exist and marine mammals. About seventy years ago, the general temperature on earth increased. Scientists attribute this to the fact that human industrial activity causes global warming. In this regard, glaciers in North America and Eurasia have melted, and the ice cover of the Arctic is disintegrating.

glacial period

The Ice Age is a stage in the geological history of the planet, which takes several million years, during which there is a decrease in temperature and an increase in the number of continental glaciers. As a rule, glaciations alternate with warmings. Now the Earth is in a period of relative increase in temperature, but this does not mean that in half a millennium the situation cannot change dramatically.

At the end of the nineteenth century, the geologist Kropotkin visited the Lena gold mines with an expedition and discovered signs of ancient glaciation there. He was so interested in the finds that he took up large-scale international work in this direction. First of all, he visited Finland and Sweden, as he suggested that it was from there that ice caps on Eastern Europe and Asia. Kropotkin's reports and his hypotheses regarding the modern ice age formed the basis contemporary ideas about this period of time.

History of the Earth

The ice age in which the Earth is now is far from the first in our history. The cooling of the climate has happened before. It was accompanied by significant changes in the relief of the continents and their movement, and also influenced the species composition of flora and fauna. Between glaciations there could be intervals of hundreds of thousands and millions of years. Each ice age is divided into glacial epochs or glacials, which during the period alternate with interglacials - interglacials.

There are four ice ages in the history of the Earth:

Early Proterozoic.

Late Proterozoic.

Paleozoic.

Cenozoic.

Each of them lasted from 400 million to 2 billion years. This suggests that our ice age has not even reached its equator yet.

Cenozoic Ice Age

Quaternary animals were forced to grow extra fur or seek shelter from ice and snow. The climate on the planet has changed again.

The first epoch of the Quaternary period was characterized by cooling, and in the second, a relative warming set in, but even now, in the most extreme latitudes and at the poles, the ice cover remains. It covers the territory of the Arctic, Antarctica and Greenland. The thickness of the ice varies from two thousand meters to five thousand.

The strongest in the entire Cenozoic era is the Pleistocene ice age, when the temperature dropped so much that three of the five oceans on the planet froze.

Chronology of the Cenozoic glaciations

The glaciation of the Quaternary period began recently, if we consider this phenomenon in relation to the history of the Earth as a whole. It is possible to distinguish separate epochs during which the temperature dropped especially low.

  1. The end of the Eocene (38 million years ago) - the glaciation of Antarctica.
  2. The entire Oligocene.
  3. Middle Miocene.
  4. Middle Pliocene.
  5. Glacial Gilbert, freezing of the seas.
  6. Continental Pleistocene.
  7. Late Upper Pleistocene (about ten thousand years ago).

This was the last major period when, due to the cooling of the climate, animals and humans had to adapt to new conditions in order to survive.

Paleozoic Ice Age

During the Paleozoic era, the Earth was so frozen that ice caps reached Africa and South America in the south, and also covered all of North America and Europe. Two glaciers almost converged along the equator. The peak is considered to be the moment when a three-kilometer layer of ice towered over the territory of northern and western Africa.

Scientists have discovered the remains and effects of glacial deposits during research in Brazil, Africa (in Nigeria) and the mouth of the Amazon River. Thanks to radioisotope analysis, it was found that the age and chemical composition of these finds are the same. So, it can be argued that the rock layers were formed as a result of one global process affecting several continents at once.

Planet Earth is still very young by cosmic standards. She is just starting her journey in the universe. It is not known whether it will continue with us or humanity will simply become an insignificant episode in successive geological epochs. If you look at the calendar, we spent a negligible amount of time on this planet, and destroying us with another cold snap is quite simple. People need to remember this and not exaggerate their role in the biological system of the Earth.

Quaternary (anthropogenic) system (period) allocated by the French scientist J. Denoyer in 1829, it is divided into four sections - lower, middle, upper and modern. The deposits are mainly represented by continental sediments. Marine sediments on the continents are not widespread. Igneous rocks - exceptionally effusive - have little development. Metamorphic rocks are unknown. The beginning of the period is characterized by a sharp cooling and periodically repeated glaciations in the northern hemisphere. At least three glaciations have been established in the north of Europe and Asia, separated by relatively warm interglacial epochs. North America also has several glaciations.

The fauna of the Quaternary period differs little from the modern one. The greatest differences are observed during the ice age, when in Europe, south of the glacier boundaries, cold-loving animal species appeared - the musk musk ox, reindeer, mammoths (Fig. 128), hairy rhinos (Fig. 129), cave bears, etc. At the beginning of the period, ancient ancestors person. In the Quaternary deposits there are bones of primitive people and traces of their life activity (fire pits, stone tools, household items, etc.). In younger Quaternary deposits since the appearance of a reasonable person (Homo sapiens) numerous tools of labor and traces of primitive culture have been preserved: the remains of drawings on the walls of caves, figurines of various animals carved from bones, etc.

From overview development of the organic world, its repeated abrupt changes during the geological history of the Earth are clearly established. Periods of magnificent development and prosperity of some groups of animals and plants are replaced by periods of decline and even total extinction. A sharp renewal of the animal world coincides with the boundaries between eras in the geochronological table. The moments of a sharp turning point in the development of the organic world and the change of fauna and flora are known in Russian literature under the name of "critical epochs". At present, five critical epochs have been established and recognized by everyone, when there was a particularly strong change in the composition of the organic world and the extinction of many organisms.

The first epoch refers to the end of the Silurian period, the second - to the end of the Paleozoic era, the third - to the end of the Triassic, the fourth - to the end of the Mesozoic and the fifth - to the end of the Paleogene. In the first critical epoch, a sharp decrease in graptolites, trilobites, nautiloids is observed, several families of brachiopods die out, a number of groups of representatives sea ​​urchins, several genera of corals, etc.

At the end of the Paleozoic in the second epoch, a much greater renewal of the organic world takes place. In the second critical epoch, completely numerous fuzulins and schwagerins, four-beam corals (rugoses) and tabulates, many families of brachiopods, sea lilies, sea urchins, the last representatives of trilobites, goniatites, many families of fish, many representatives of amphibians - stegocephals, etc. also disappear. representatives of ferns.

The third era is coming to an end Triassic period when most of the families and genera of the Triassic ammonites, the last stegocephals and some reptiles die out. In the fourth critical epoch, ammonites and belemnites, some families of protozoa, pelecypods, brachiopods, sea lilies, terrestrial, aquatic and air reptiles, toothy birds, etc. die out. In the fifth epoch, at the end of the Paleogene, nummulites, many representatives of mammals, etc., die out.

Extinct animals are replaced by animals of other families, classes and genera, the remains of which are unknown in more ancient layers.

From the analysis of the geochronological table, it can be seen that major changes in the composition of vegetation do not correspond to critical epochs and do not correspond to the boundaries of eras, which are established on the basis of the development of animals. Vegetation is far ahead of animals in its development. The change in vegetation types does not correspond to critical epochs, epochs of extinction and fauna renewal. Paleozoic vegetation undergoes major changes already in the Permian period. Many representatives of carboniferous ferns die out in the Early Permian. In the late Permian, gymnosperms were already widely developed, which are the most characteristic and predominant plants of the Mesozoic era.

At the end of the Mesozoic (in the deposits of the upper Lower Cretaceous), the first angiosperms (deciduous, flowering, cereals) appear, which in the Late Cretaceous and the Cenozoic era are the dominant types of flora.

Thus, changes in the composition of vegetation occurred much earlier than changes in the composition of fauna, about half and even slightly more than half of the geological period. Accordingly, the eras of development of various forms of vegetation are distinguished under the names: 1) paleophyte (ancient plants), covering the end of the Proterozoic, Cambrian, Ordovician, Silurian, Devonian, Carboniferous and early Permian; 2) mesophytic (medium plants), including late Permian, Triassic, Jurassic periods and early Cretaceous; 3) cenophyte, or neophyte (new modern plants), begins from the Late Cretaceous and continues to the present day.

The process of development of the organic world in geological history was far from uniform. Moments of magnificent prosperity of some groups of animals are replaced by epochs of slow, gradual decline and complete extinction of previously flourishing animals. These periodic changes in the development of the animal world are explained by the significant variability of physical and geographical conditions throughout the entire geological history of the Earth's development. The physical and geographical situation did not remain constant, unchanged, but changed repeatedly in the Paleozoic, Mesozoic and Cenozoic. The change in physical and geographical conditions influenced the change in the organic world. The change in physical and geographical conditions, in turn, was determined by the causes that caused the development of the Earth, and manifested itself in the form of major mountain-building movements that were repeatedly repeated in the geological history of the development of our planet.

A sharp change in the organic world coincides with major mountain-building movements, which in their significance are revolutionary periods in the history of the development of the Earth. It turns out that the first mass extinction of animals coincides with the major mountain-building movements of the Caledonian folding, which ended at the border of the Silurian and Devonian. The second extinction - at the end of the Paleozoic - coincides with the last phases of the Hercynian folding, which ended at the border of the late Permian and Mesozoic. The third epoch coincides with the ancient Cimmerian phase of the Mesozoic folding, which took place on the border of the Triassic and jurassic periods. The fourth epoch is synchronous with the largest Laramian phase of the Alpine folding. And finally, the fifth epoch, dated to the end of the Paleogene, coincides with the so-called Savian phases of Alpine tectogenesis.

The periods of these mountain building movements were periods of very strong changes in physical and geographical conditions. These movements had a very significant impact not only on the distribution of land and ancient seas, but also on changes in the relief of ancient continents and the depth of the seas. They sometimes caused a sharp change in climate and environment and sharply disrupted the environment to which organisms had adapted. The new environment necessitated the adaptation of organisms to the new environment. Some organisms quickly adapted to the new environment and withstood the struggle for existence. Other animals, especially those with a pronounced specialization, were unable to quickly adapt to the new conditions of existence, could not withstand competition with other animal species and completely died out. The extinction of the same groups or species of animals developed in different parts of the ancient continents and seas did not occur simultaneously. First, there was a significant reduction in the number of representatives of a certain group of animals, and then a reduction in the areas of distribution, and, finally, the widespread extinction of the group.

The extinction of some animal species is closely connected with the development of other, more advanced forms. Throughout geological time, natural selection has been observed among the organic world.

The coincidence of periods of intense mountain-building movements with the eras of extinction and renewal of the organic world is far from accidental, but has a completely natural character in the history of the development of the organic world. During periods of revolutions in the development of the organic world, there are large "jumps", the death of the old and the emergence of the new, represented by more advanced forms among the animal and plant worlds. During the period of relative tectonic calm, when there was no abrupt change physical and geographical conditions and environment, there is a gradual development, gradual evolution of the organic world. During these periods, there is usually no sharp renewal of the organic world, characteristic of revolutionary periods in the development of the Earth.