When did the Jurassic period begin and end? Jurassic period

Jurassic geological period, Jura, Jurassic system, middle period mesozoic. Began 200-199 million years ago. n. and ended with 144 million liters. n.

For the first time deposits of this period were discovered and described in the Jura (mountains in Switzerland and France), hence the name of the period. The deposits of the Jurassic period are very diverse: limestones, clastic rocks, shales, igneous rocks, clays, sands, conglomerates formed in a variety of conditions. The deposits of that time are quite diverse: limestones, clastic rocks, shales, igneous rocks, clays, sands, conglomerates formed in a variety of conditions.

Jurassic tectonics: At the beginning of the Jurassic, the single supercontinent Pangea began to break up into separate continental blocks. Shallow seas formed between them. Intensive tectonic movements at the end of the Triassic and at the beginning of the Jurassic contributed to the deepening of the large bays that gradually separated Africa and Australia from Gondwana. The gulf between Africa and America deepened. Depressions formed in Eurasia: German, Anglo-Paris, West Siberian. The Arctic Sea flooded the northern coast of Laurasia. It is thanks to this that the climate of the Jurassic period became more humid. In the Jurassic, the outlines of the continents begin to form: Africa, Australia, Antarctica, North and south america. And although they are located differently than now, they formed precisely in the Jurassic period.

Climate and vegetation of the Jurassic period

The volcanic activity of the end of the Triassic - the beginning of the Jurassic period caused the transgression of the sea. The continents separated and the climate in the Jurassic became more humid than in the Triassic. In place of the deserts of the Triassic period, lush vegetation grew in the Jurassic period. Huge areas were covered with lush vegetation. The forests of the Jurassic period mainly consisted of ferns and gymnosperms.

The warm and humid climate of the Jurassic period contributed to the exuberant development flora planets.

Ferns, conifers, and cycads formed extensive marshy forests. Araucaria, arborvitae, cicadas grew on the coast. Ferns and horsetails formed extensive woodlands. At the beginning of the Jurassic, about 195 million years. n. throughout the northern hemisphere, the vegetation was rather monotonous. In the northern vegetation belt ginkgo and herbaceous ferns predominated. In the Jurassic period, Ginkgoaceae were very widespread. Groves of ginkgo trees grew throughout the belt.

In the southern vegetation belt, cycads and tree ferns predominated.

Ferns of the Jurassic period have survived to this day in some parts wildlife. Horsetails and club mosses almost did not differ from modern ones.

animals: Jurassic period Dawn of the Age of Dinosaurs. It was the violent development of vegetation that contributed to the emergence of many species of herbivorous dinosaurs. The growth in the number of herbivorous dinosaurs gave impetus to the growth in the number of predators. Dinosaurs settled all over the land and lived in forests, lakes, swamps. The range of differences between them is so great that family ties between them are installed with great difficulty. The variety of dinosaur species in the Jurassic period was great. They could be the size of a cat or a chicken, or they could reach the size of huge whales.

The Jurassic period is the time of the dwelling of many famous dinosaurs. Of the lizards, these are Allosaurus and Diplodocus. Of the ornithischians, this is a stegosaurus.

In the Jurassic period, winged lizards - pterosaurs reigned supreme in the air. They appeared in the Triassic, but their heyday was in the Jurassic period. Pterosaurs were represented by two groups of pterodactyls and rhamphorhynchus.

In the Jurassic period, the first birds appear, or something in between birds and lizards. Creatures that appeared in the Jurassic period and have the properties of lizards and modern birds are called Archeopteryx. The first birds are Archeopteryx, the size of a dove. Archeopteryx lived in forests. They fed mainly on insects and seeds.

Bivalves displace brachiopods from shallow waters. Brachiopod shells are replaced by oysters. Bivalve molluscs fill all the vital niches of the seabed. Many stop collecting food from the ground and move on to pumping water with the help of gills. in warm and shallow seas other important events took place during the Jurassic period.

The Jurassic period gave rise to many species of plesiosaurs and ichthyosaurs that rivaled the fast-moving and extremely agile sharks. bony fish. and in sea ​​depths Leopleuradon patrolled its territory non-stop in search of food.

But one creature could rightfully be called the master of the Jurassic seas. This is a giant Liopleurodon weighing up to 25 tons. Liopleurodon was the most dangerous predator seas of the Jurassic period, and possibly throughout the history of the planet.

And was replaced by chalk, and had a duration of about 56 million years.

Geography and climate

During the Jurassic period, the supercontinent Pangea began to split into two separate continents:

• northern part known as Laurasia (which eventually split into North America and Eurasia, opening up basins to Atlantic Ocean, and the Gulf of Mexico)
• the southern part - Gondwana - drifted east (and eventually split into Antarctica, Madagascar, India and Australia, and its West Side, formed Africa, and South America).

This process of dividing Pangea, along with warmer global temperatures, allowed reptiles such as dinosaurs to diversify and dominate Earth for a long time.

plant life

During the Mesozoic era, plants developed the ability to lead a terrestrial lifestyle and not be limited only to the oceans. By the beginning of the Jurassic, life was from bryophytes, stunted bryophytes, and liverworts, which had no vascular tissue and were limited to wet swampy areas.

ginkgo trees

Ferns and gingkos, which have roots and vascular tissue for transporting water, and nutrients, as well as spore-reproducing, were the dominant plants of the early Jurassic. During the Jurassic period appeared new way plant reproduction. Gymnosperms, such as conifers, have developed pollen that is dispersed over long distances by the wind and pollinates female cones. This method of reproduction made it possible to significantly increase the number of gymnosperms by the end of the Jurassic. Flowering plants did not evolve until the Cretaceous.

Age of dinosaurs

As shown in the movie Jurassic Park, reptiles were the dominant animal life form during the Jurassic period. They overcame evolutionary obstacles that limited . Reptiles had strong ossified skeletons with advanced muscular systems to support and move the body. Some of the largest animals that ever lived were Jurassic dinosaurs. Reptiles could also develop amniotic eggs that were incubated on land.

sauropods

Sauropods (lizard-footed dinosaurs) are herbivorous quadrupeds, with long necks and heavy tails. Many sauropods, such as brachiosaurs, were huge. Representatives of some genera had a body length of about 25 m, and the weight ranged from 50-100 tons, which makes them the largest land animals that have ever existed on Earth. Their skulls were relatively small, with nostrils set high towards their eyes. Such small skulls meant very small brains. Despite their small brains, this group of animals flourished during the Jurassic and had a wide geographic distribution. Sauropod fossils have been found on every continent, with the exception of Antarctica. Other famous dinosaurs the Jurassic includes stegosaurs and flying pterosaurs.

Carnosaurs were one of the main predators mesozoic era. The genus Allosaurus was one of the most common carnosaurs in North America. They are similar to later tyrannosaurs, although studies have shown that they have little in common. Allosaurus had strong hind limbs, heavy forelegs, and long jaws.

early mammals

Adelobasileus

Dinosaurs may have been the dominant land animals, but not the only fauna. Early mammals were mostly very small herbivores or insectivores, and did not compete with larger reptiles. Adelobasileus is the predatory ancestor of mammals. He had a special structure of the inner ear and jaws. This animal appeared at the end of the Triassic period.

In August 2011, scientists from China announced the discovery of Yuramaya. This tiny mid-Jurassic animal caused a stir among scientists because it was a clear ancestor placental mammals, indicating that mammals evolved much earlier than previously thought.

Sea life

Plesiosaur

The Jurassic period was also very diverse. the largest marine predators were plesiosaurs. These carnivorous marine reptiles usually had broad bodies and long necks with four flipper-shaped limbs.

Ichthyosaurus - a marine reptile, was most common in the early Jurassic period. Since some fossils have been found with smaller members of their species inside their bodies, it is suggested that these animals may have been among the first to have internal pregnancy and give birth to live young.

Cephalopods were also widespread during the Jurassic and included the ancestors of modern squid. Among the most beautiful fossils marine life spiral shells of ammonites can be distinguished.

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Jurassic period- This is the second (middle) period of the Mesozoic era. It begins 201 million years before our times, lasts 56 million years and ends 145 million years ago (according to other sources, the duration of the Jurassic period is 69 million years: 213 - 144 million years). Named after mountains Yura, in which its sedimentary layers were first identified. Significant for the widespread flowering of dinosaurs.

The main subdivisions of the Jurassic period, its geography and climate

According to the classification adopted by the International Union of Geological Sciences, The Jurassic period is divided into three divisions- Lower - Leias (stages - Gottangsky, Sinemursky, Plinsbachsky, Toarsky), Middle - Dogger (levels - Aalensky, Bayossky, Batsky, Callovian) and Upper Small (levels - Oxford, Kimmeridgsky, Tithonian).

Jurassic period	Departments	Tiers
	Leyas (Lower)	Goettansky
		Sinemursky
		Plinsbachsky
		Toarian
	Dogger (Medium)	Aalen
		Bayosian
		Bath
		Callovian
	Small (Upper)	Oxford
		Kimmeridge
		titonian

In this period, the division of Pangea into constituent blocks - the continents - continued. Upper Laurentia, which later became North America and Europe, finally separated from Gondwana, which again began to shift south. As a result, the connection between the global continents was broken, which had an important impact on the further evolution and development of flora and fauna. The differences that originated at that time are sharply expressed to this day.

The Tethys Sea, expanded even more as a result of the separation of the continents, now occupied most of modern Europe. It originated from the Iberian Peninsula and, crossing the south and southeast of Asia diagonally, went into Pacific Ocean. Most of present France, Spain and England was under his warm waters. On the left, as a result of the separation of the North American sector of Gondwana, a depression began to emerge, which in the future became the Atlantic Ocean.

With the start of the Jurassic era average temperature on the globe gradually began to decline, and therefore in the lower section Jurassic climate was close to moderate - subtropical. But closer to the middle, the temperature began to rise again, and by the beginning of the Cretaceous period, the climate became greenhouse.

The ocean level rose and fell slightly throughout the Jurassic, but average height sea ​​level was an order of magnitude higher than in the Triassic. As a result of the divergence of continental blocks, a great many small lakes were formed, in which both vegetation and animal life, so that the quantitative and qualitative level of flora and fauna of the Jurassic period soon caught up and outstripped the level of the Permian to the point of global mass extinction.

sedimentation

With a drop in temperature, multiple precipitation began to fall abundantly throughout the earth, which contributed to the advancement of vegetation, and then the animal world, into the depths of the continents, which is due to Jurassic sedimentation. But the most intense for this period are the products of formation earth's crust under the influence of continental shifts, and as a result - volcanic and other seismic activity. These are various igneous, clastic rocks. Large deposits of shale, sand, clay, conglomerates, limestone.

The warm and stable climate of the Jurassic period greatly contributed to the rapid development, formation and evolutionary improvement of both old and new life forms. (Fig. 1) have risen to a new level compared to the sluggish, not especially shining varieties, the Triassic.

Rice. 1 - Jurassic Animals

The Jurassic seas were full of various marine invertebrates. Especially numerous were belemnites, ammonites, all kinds of sea ​​lilies. And although there were an order of magnitude fewer ammonites in the Jurassic than in the Triassic, they mostly had a more developed body structure than their ancestors from the previous era, with the exception of the phyloceras, which did not change at all during the millions of years of transition from the Triassic to the Jurassic. It was at that time that many ammonites acquired their indescribable mother-of-pearl coating, which has survived to this day. Ammonites were found in large quantities, both in the distant oceanic depths and in coastal warm and inland seas.

Belemnites in the Jurassic era reached an unprecedented development. They huddled in flocks and plowed the depths of the sea in search of gaping prey. Some of them at that time reached three meters in length. The remains of their shells, nicknamed by scientists "devil's fingers" are found in the sediments of the Jurassic period almost everywhere.

Bivalve mollusks belonging to oyster varieties were also numerous. In that era, they began to form a kind of oyster jars. Received a boost in development and numerous sea ​​urchins, abundantly inhabiting reef areas at that time. Some of them have successfully survived to our time. But many, such as hedgehogs of irregular shapes elongated along the length, which had a jaw apparatus, died out.

Insects have also taken a big step forward. Their visual, flying and other devices improved more and more. More and more varieties appeared among the barnacles, decapods, leaf-footed crustaceans, most of the freshwater sponges and caddisflies multiplied and evolved. Ground jurassic insects replenished with new varieties of dragonflies, beetles, cicadas, bedbugs, etc. Along with the emergence of a huge number of flowering plants, began to appear and a large number of pollinating insects that feed on flower nectar.

But it was the reptiles that reached the greatest development in the Jurassic era - dinosaurs. By the middle of the Jurassic period, they completely took over all the land areas, displacing or destroying their reptilian predecessors, from which they originated, in pursuit of food.

In the depths of the sea, already at the beginning of the Jurassic period, reigned supreme dolphin-like ichthyosaurs. Their long heads had strong, oblong jaws studded with rows of sharp teeth, and large, highly developed eyes were framed by bone-plate rings. By the middle of the period, they turned into real giants. The length of the skull of some ichthyosaurs reached 3 meters, and the body length exceeded 12 meters. The limbs of these aquatic reptiles evolved under the influence of underwater life and consisted of simple bone plates. Elbows, metatarsus, hands and fingers ceased to differ from each other, one huge flipper supported more than a hundred bone plates of various sizes. The shoulder girdle, as well as the pelvic girdle, became underdeveloped, but this was not necessary, since additionally grown powerful fins provided them with mobility in the aquatic environment.

Another reptile that seriously and permanently settled in the depths of the sea was plesiosaur. They, like ichthyosaurs, originated in the seas as early as the Triassic period, but in the Jurassic period they branched into two varieties. Some had long neck and a small head (plesiosaurs), in others the head became an order of magnitude larger, and the neck was much shorter, which made them look more like underdeveloped crocodiles. Both, unlike ichthyosaurs, still needed to rest on land, and therefore often crawled out onto it, becoming the prey of land giants there, such as, for example, a tyrannosaurus rex or herds of smaller predatory reptiles. Very nimble in the water, on land they were clumsy fur seals our time. Pliosaurs were much more agile in the water, but what plesiosaurs lacked in agility was made up for by their long necks, thanks to which they instantly grabbed prey, no matter what position their body was in.

In the Jurassic period, all kinds of fish multiplied unusually. The water depths literally teemed with a motley variety of coral ray-finned, cartilaginous and ganoid. Sharks with stingrays were also diverse, which, due to their extraordinary agility, speed and agility, developed over hundreds of millions of years of evolution, still constituted Jurassic underwater reptile predators. Also during this period, many new varieties of turtles and toads appeared.

But the terrestrial variety of reptile dinosaurs was truly outstanding. (Fig. 2) were from 10 cm to 30 meters in height. Many of them were simple harmless herbivores, but often came across and ferocious predators.

Rice. 2 - Jurassic Dinosaurs

One of the largest herbivorous dinosaurs was brontosaurus(now Apatosaurus). His body weighed 30 tons, the length from head to tail reached 20 meters. And despite the fact that his height at the shoulders reached only 4.5 meters, with the help of a neck that reached a length of up to 5-6 meters, they perfectly ate tree foliage.

But most huge dinosaur of that era, as well as the absolute champion among all the animals of the Earth of all time, was a 50-ton herbivore brachiosaurus. With a body length of 26 m, he had such a long neck that when it stretched up, his small head was 13 meters above the ground. To feed, this huge reptile needed to absorb up to 500 kg of green mass daily. It is noteworthy that with such a truly gigantic body size, his brain weighed no more than 450 grams.

It is appropriate to say a few words about predators, of which there were also many in the Jurassic period. The most gigantic and dangerous predator of the Jura is considered a 12-meter tyrannosaurus rex, but as scientists have proven, this predator was more opportunistic in its views on food. He rarely hunted, often preferring carrion. But they were truly dangerous. allosaurs. With a height of 4 meters and a length of 11 meters, these reptile predators hunted prey many times greater than them in terms of weight and other parameters. Often they, having huddled in a herd, attacked such herbivorous giants of that era as Camarasaurus (47 tons) and the aforementioned Apatosaurus.

Came across more small predators, for example, such as 3-meter dilophosaurus, weighing only 400 kg, but straying into a flock, attacking even larger predators.

In view of the ever-increasing danger from predatory individuals, evolution has rewarded some herbivorous individuals with formidable elements of protection. For example, such a herbivorous dinosaur as Kentrosaurus was endowed with elements of protection in the form of huge sharp spikes on the tail and sharp plates along the ridge. The spikes were so large that, with a strong blow, the Kentrosaurus would have pierced through such a predator as a Velociraptor or even a Dilophosaurus.

With all that animal world Jurassic has been carefully balanced. The herbivorous lizard population was controlled by predatory lizards, predators were kept in check by many smaller predators and aggressive herbivores like stegosaurs. Thus, the natural balance was maintained for many millions of years, and what caused the extinction of dinosaurs in Cretaceous so it is still not known.

By the middle of the Jurassic air space was filled with many flying dinosaurs such as pterodactyls and other pterosaurs. They glide quite skillfully in the air, but in order to take to the skies, they need to climb imposing hills. These, for the most part, were not very mobile examples of ancient mammals, but from the air they could very successfully track down and attack prey in a flocking manner. Smaller representatives of flying dinosaurs preferred to make do with carrion.

In the sediments of the Jurassic period, the remains of a fledged lizard Archeopteryx were found, which for a long time was considered by scientists to be the ancestor of birds. But, as recently scientifically proven, this variety of lizards was a dead end. Birds evolved mainly from other varieties of reptiles. Archeopteryx had a long feathered tail, jaws studded with small teeth, and feathered wings had developed fingers, with which the animal grabbed branches. Archeopteryxes flew poorly, mainly gliding from branch to branch. Basically, they preferred to climb tree trunks, digging into their bark and branches with sharp curved claws. It is noteworthy that in our time, fingers on the wings remained only in the chicks of the hoatzin bird.

The first birds, in the form of small dinosaurs, jumped high either in their attempts to reach out for insects fluttering in the sky, or in order to escape from predators. In the process of evolution, they were increasingly overgrown with plumage, their jumps became longer and longer. In the process of jumping, future birds helped themselves more and more intensively, waving their forelimbs. Over time, their now wings, and not just forelimbs, acquired more and more powerful muscles, and the structure of their bones became hollow, as a result of which total weight birds became much easier. And all this led to the fact that by the end of the Jurassic period, along with pterosaurs, a large number of all kinds of ancient birds plowed the airspace of the Jura.

In the Jurassic period, they actively multiplied and small mammals. But still, they were not allowed to express themselves in breadth, because the ubiquitous power of dinosaurs was too overwhelming.

Since, in the process of climate change, the vast deserts of the Triassic began to be abundantly irrigated with precipitation, this created the prerequisites for the advancement of vegetation even deeper into the continents, and closer to the middle of the Jurassic, almost the entire surface of the continents was covered with lush vegetation.

All low-lying places are abundantly overgrown with ferns, cicadas and coniferous thickets. The coasts of the seas were occupied by araucaria, thuja and, again, cicadas. Also, vast land masses were occupied by ferns and horsetails. Despite the fact that by the beginning of the Jurassic period, the vegetation on the continents of the northern hemisphere was relatively uniform, by the middle of the Jurassic, two main belts of plant masses, already established and strengthened, were formed - the northern and southern.

northern belt was notable for the fact that at that time it was formed mainly by ginkgo plants mixed with herbaceous ferns. With all that is half the whole vegetation northern latitudes jurassic consisted of Ginkgo varieties, today only one species of these plants has miraculously survived.

Southern belt were mainly cycads and tree ferns. At all Jurassic period plants(Fig. 3) more than half still consisted of various ferns. Horsetails and club mosses of those times almost did not differ from the current ones. In those places where cordaite and ferns grew massively during the Jurassic, this moment growing tropical cycad jungle. Of the gymnosperms, cycads were the most common in the Jurassic. Today they can only be found in tropical and subtropical zones. It was them, reminiscent of modern palm trees with their crowns, that most herbivorous dinosaurs ate.

Rice. 3 - Plants of the Jurassic period

In the Jurassic period northern latitudes deciduous Ginkgoaceae began to appear for the first time. And in the second half of the period, the first spruce and cypress trees appeared. coniferous forests The Jurassic very much looked like a modern one.

Minerals of the Jurassic period

The most pronounced minerals related to the Jurassic period are European and North American chromite deposits, Caucasian and Japanese copper-pyrite deposits, Alpine deposits of manganese ores, tungsten ores of the Verkhoyansk-Chukotka region, Transbaikalia, Indonesia, North American Cordilleras. Also to this era can be attributed deposits of tin, molybdenum, gold and other rare metals scattered everywhere, formed in the late Cimmerian era and thrown to the surface due to granitoid mechanisms associated with the separation of the continents that took place at the end of the Jurassic period. Numerous and ubiquitous iron ore deposits. There are deposits of uranium ores on the Colorado Plateau.

According to modern ideas of scientists, the geological history of our planet is 4.5-5 billion years. In the process of its development, it is customary to single out geological periods Earth.

general information

The geological periods of the Earth (table below) are a sequence of events that have occurred in the process of the development of the planet since the formation of the earth's crust on it. Over time, various processes occur on the surface, such as the emergence and destruction of land areas under water and raising them, glaciation, as well as the appearance and disappearance different types plants and animals, etc. Our planet bears obvious traces of its formation. Scientists claim that they are able to fix them with mathematical accuracy in various layers of rocks.

Main sediment groups

Geologists, trying to reconstruct the history of the planet, study rock layers. It is customary to divide these deposits into five main groups, highlighting the following geological eras Lands: ancient (Archaean), early (Proterozoic), ancient (Paleozoic), middle (Mesozoic) and new (Cenozoic). It is believed that the boundary between them runs along the largest evolutionary phenomena that have occurred on our planet. The last three eras, in turn, are divided into periods, since the remains of plants and animals are most clearly preserved in these deposits. Each stage is characterized by events that have had a decisive influence on the current relief of the Earth.

oldest stage

The Earth was distinguished by rather violent volcanic processes, as a result of which igneous granite rocks appeared on the surface of the planet - the basis for the formation of continental plates. At that time, only microorganisms existed here that could do without oxygen. It is assumed that deposits archean era they cover certain areas of the continents with an almost solid shield, they contain a lot of iron, silver, platinum, gold and ores of other metals.

early stage

It is also characterized by high volcanic activity. During this period, mountain ranges of the so-called Baikal folding were formed. To this day, they have practically not survived, today they are just separate insignificant uplifts on the plains. During this period, the Earth was inhabited by the simplest microorganisms and blue-green algae, the first multicellular organisms appeared. The Proterozoic rock layer is rich in minerals: mica, non-ferrous metal ores and iron ores.

ancient stage

The first period of the Paleozoic era was marked by the formation of mountain ranges. This led to a significant reduction in sea basins, as well as the emergence of huge land areas. Separate ranges of that period have survived to this day: in the Urals, in Arabia, Southeast China and Central Europe. All these mountains are "worn out" and low. The second half of the Paleozoic is also characterized by mountain building processes. Ranges were formed here. This era was more powerful, vast mountain ranges arose in the territories of the Urals and Western Siberia, Manchuria and Mongolia, Central Europe, as well as Australia and North America. Today they are represented by very low blocky massifs. Animals of the Paleozoic era are reptiles and amphibians, the seas and oceans are inhabited by fish. Among the flora, algae predominated. Palaeozoic characterized by large deposits hard coal and oil, which arose precisely in this era.

middle stage

The beginning of the Mesozoic era is characterized by a period of relative calm and the gradual destruction of the mountain systems created earlier, the submersion of flat territories (part of Western Siberia) under water. The second half of this period was marked by the formation of Mesozoic folding ridges. Very vast mountainous countries appeared, which today have the same appearance. Mountains are an example. Eastern Siberia, Cordillera, parts of Indochina and Tibet. The ground was densely covered with lush vegetation, which gradually died off and rotted away. Thanks to hot and humid climate there was an active formation of peat bogs and swamps. It was the era of giant lizards - dinosaurs. The inhabitants of the Mesozoic era (herbivores and predatory animals) spread throughout the entire planet. At the same time, the first mammals appear.

New stage

The Cenozoic era, which replaced the middle stage, continues to this day. The beginning of this period was marked by an increase in the activity of the internal forces of the planet, which led to a general uplift of huge areas of land. This era is characterized by the emergence of mountain ranges within the Alpine-Himalayan belt. During this period, the Eurasian continent acquired its modern shape. In addition, there was a significant rejuvenation of the ancient massifs of the Urals, Tien Shan, Appalachians and Altai. The climate on Earth changed dramatically, periods of powerful ice cover began. The movements of glacial masses changed the relief of the continents. As a result, hilly plains with a huge number of lakes were formed. Animals cenozoic era- these are mammals, reptiles and amphibians, many representatives of the initial periods have survived to this day, others have died out (mammoths, woolly rhinos, saber-toothed tigers, cave bears and others) for one reason or another.

What is a geologic period?

The geological stage as a unit of our planet is usually divided into periods. Let's see what the encyclopedia says about this term. Period (geological) is a large interval of geological time during which rocks. In turn, it is subdivided into smaller units, which are commonly called epochs.

The first stages (Archaean and Proterozoic), due to the complete absence or insignificant amount of animal and vegetable deposits in them, are not usually divided into additional sections. The Paleozoic era includes the Cambrian, Ordovician, Silurian, Devonian, Carboniferous and Permian periods. This stage is characterized the largest number subintervals, the rest were limited to only three. The Mesozoic era includes the Triassic, Jurassic and Cretaceous stages. The Cenozoic era, the periods of which are most studied, is represented by the Paleogene, Neogene and Quaternary subinterval. Let's take a closer look at some of them.

Triassic

The Triassic period is the first subinterval of the Mesozoic era. Its duration was about 50 million years (beginning - 251-199 million years ago). It is characterized by the renewal of marine and terrestrial fauna. At the same time, a few representatives of the Paleozoic continue to exist, such as spiriferids, tabulata, some laminabranchs, and others. Among the invertebrates, ammonites are very numerous, giving rise to many new forms important for stratigraphy. Among corals, six-rayed forms predominate, among brachiopods - terebratulids and rhynchonelids, in the group of echinoderms - sea urchins. Vertebrate animals are mainly represented by reptiles - large lizard dinosaurs. Thecodonts are widespread land reptiles. Besides, in Triassic the first large inhabitants aquatic environment- ichthyosaurs and plesiosaurs, however, they reach their heyday only in the Jurassic period. Also at this time, the first mammals arose, which were represented by small forms.

Flora in the Triassic period (geological) loses elements of the Paleozoic and acquires an exclusively Mesozoic composition. Fern species of plants, sago-like, coniferous and ginkgoales predominate here. Climatic conditions characterized by significant warming. This leads to the drying up of many inland seas, and in the remaining seas the level of salinity increases significantly. In addition, the areas of inland water bodies are greatly reduced, resulting in the development of desert landscapes. For example, the Tauride formation of the Crimean peninsula belongs to this period.

Yura

The Jurassic period got its name from the Jura Mountains in Western Europe. It constitutes the middle part of the Mesozoic and most closely reflects the main features of the development of the organics of this era. In turn, it is usually divided into three sections: lower, middle and upper.

The fauna of this period is represented by widely distributed invertebrates - cephalopods (ammonites, represented by numerous species and genera). They sharply differ from representatives of the Triassic in sculpture and character of shells. In addition, in the Jurassic period, another group of mollusks, the belemnites, flourished. At this time, six-ray reef-forming corals, lilies and urchins, as well as numerous lamellar gills, reach significant development. On the other hand, species of the Paleozoic brachiopod completely disappear. marine fauna vertebrate species significantly different from the Triassic, it reaches a huge diversity. In the Jurassic period, fish are widely developed, as well as aquatic reptiles - ichthyosaurs and plesiosaurs. At this time, there is a transition from land and adaptation to marine environment crocodiles and turtles. A huge variety is achieved by various types of terrestrial vertebrates - reptiles. Among them, dinosaurs come to their heyday, which are represented by herbivores, carnivores and other forms. Most of them reach 23 meters in length, for example, diplodocus. The deposits of this period contain the new kind reptiles - flying lizards, which are called "pterodactyls". At the same time, the first birds appear. The flora of the Jura reaches a luxuriant flowering: gymnosperms, ginkgos, cycads, conifers (araucaria), bennettites, cycads and, of course, ferns, horsetails and club mosses.

Neogene

The Neogene period is the second period of the Cenozoic era. It began 25 million years ago and ended 1.8 million years ago. Significant changes in the composition of the fauna took place at this time. A wide variety of gastropods and bivalves, corals, foraminifers, and coccolithophores emerge. Amphibians have been widely developed sea ​​turtles and bony fish. IN neogene period terrestrial vertebral forms also reach great diversity. For example, rapidly progressing hipparion species appeared: hipparions, horses, rhinos, antelopes, camels, proboscis, deer, hippos, giraffes, rodents, saber-toothed tigers, hyenas, great apes and others.

Under the influence of various factors, the organic world rapidly evolves at this time: forest-steppes, taiga, mountain and flat steppes appear. In tropical areas, savannas and moist forests. Climatic conditions are approaching modern ones.

Geology as a science

The geological periods of the Earth are studied by science - geology. It appeared relatively recently - at the beginning of the 20th century. However, despite her youth, she is able to shed light on many contentious issues about the formation of our planet, as well as the origin of the creatures inhabiting it. There are few hypotheses in this science, mainly only the results of observations and facts are used. There is no doubt that the traces of the development of the planet stored in the earth's layers will in any case give a more accurate picture of the past than any written book. However, not everyone is able to read these facts and understand them correctly, therefore, even in this exact science, erroneous interpretations of certain events can occur from time to time. Where traces of fire are present, it is safe to say that there was fire; and where there are traces of water, with the same certainty it can be argued that there was water, and so on. And yet, mistakes also happen. In order not to be unfounded, consider one such example.

"Frost patterns on glass"

In 1973, the journal "Knowledge is Power" published an article by the famous biologist A. A. Lyubimtsev " Frost patterns on glass." In it, the author draws the attention of readers to the striking similarity of ice patterns with plant structures. As an experiment, he photographed a pattern on glass and showed the photo to a botanist he knew. And without slowing down, he recognized the petrified footprint of a thistle in the picture. From the point of view of chemistry, these patterns arise due to the gas-phase crystallization of water vapor. However, something similar occurs in the production of pyrolytic graphite by pyrolysis of methane diluted with hydrogen. Thus, it was found that dendritic forms are formed away from this flow, which are very similar to plant remains. This is explained by the fact that there are general laws that govern the formation of forms in inorganic matter and wildlife.

For a long time, geologists have dated each geologic period based on traces of plant and animal forms found in coal deposits. And only a few years ago there were statements by some scientists that this method was wrong and that all the fossils found were nothing more than a by-product of the formation earth layers. There is no doubt that everything cannot be measured in the same way, but it is necessary to approach dating issues more carefully.

Was there a global glaciation?

Let's consider one more categorical statement of scientists, and not only geologists. All of us, starting from school, were taught about the global glaciation that covered our planet, as a result of which many animal species became extinct: mammoths, woolly rhinos and many others. And the modern younger generation is brought up on the quadrology "Ice Age". Scientists unanimously argue that geology - exact science, which does not allow theories, but uses only proven facts. However, this is not the case. Here, as in many areas of science (history, archeology, and others), one can observe the rigidity of theories and the steadfastness of authorities. For example, since the end of the nineteenth century, in the margins of science, there have been heated debates about whether there was a glaciation or not. In the middle of the twentieth century, the famous geologist I. G. Pidoplichko published a four-volume work “On ice age". In this work, the author gradually proves the inconsistency of the version of global glaciation. He relies not on the works of other scientists, but on the geological excavations he personally carried out (moreover, he carried out some of them, being a soldier of the Red Army, participating in battles against the German invaders) throughout the territory Soviet Union And Western Europe. He proves that the glacier could not cover the entire continent, but was only local in nature, and that it did not cause the extinction of many animal species, but completely different factors - these are catastrophic events that led to the pole shift (“Sensational history of the Earth”, A. Sklyarov); And economic activity the person himself.

Mysticism, or Why scientists do not notice the obvious

Despite the irrefutable evidence provided by Pidoplichko, scientists are in no hurry to abandon the accepted version of glaciation. And then even more interesting. The author's works were published in the early 1950s, but with the death of Stalin, all copies of the four-volume edition were confiscated from the libraries and universities of the country, were preserved only in the library vaults, and it is not easy to get them from there. IN Soviet time everyone who wanted to borrow this book from the library was registered by the special services. And even today there are certain problems in obtaining this printed edition. However, thanks to the Internet, everyone can get acquainted with the works of the author, who analyzes in detail the periods geological history planets, explains the origin of certain traces.

Geology - an exact science?

It is believed that geology is an exceptionally experimental science, which draws conclusions only from what it sees. If the case is doubtful, then she does not state anything, expresses an opinion that allows for discussion, and postpones the final decision until unambiguous observations are received. However, as practice shows, the exact sciences are also wrong (for example, physics or mathematics). Nevertheless, mistakes are not a disaster if they are accepted and corrected in time. Often they are not global in nature, but have local significance, you just need to have the courage to accept the obvious, draw the right conclusions and move on towards new discoveries. Modern scientists show a radically opposite behavior, because most of the luminaries of science at one time received titles, awards and recognition for their work, and today they do not want to part with them at all. And such behavior is noticed not only in geology, but also in other fields of activity. Only strong people they are not afraid to admit their mistakes, they rejoice at the opportunity to develop further, because the discovery of an error is not a disaster, but, on the contrary, a new opportunity.