The modern geological era. What era is it?
To understand what era is now, you need to lookto the decision of the II session of the International Geological Congress, held in 1881. Then the scientists argued about the geological chronology of our planet. There were several points of view, which brought trouble to science. By a general vote of experts, it was decided that the modern geological era is Cenozoic. It began 66 million years ago and continues to this day.
Features of the Cenozoic
Of course, the modern geological era isnot something monolithic and monotonous. It is divided into three periods: Paleogene, Neogene and Quaternary. During this time, the world has changed dramatically. In the early stages of the Cenozoic, the Earth looked completely different from today, including in terms of flora and fauna. However, it was then that several events occurred, as a result of which the planet became as we know it.
The restructuring of the world system beganinterconnected sea currents. It was caused by an unprecedented continental drift. Its consequence was the complication of heat exchange between the equatorial and polar basins.
The Gondwana supercontinent is split in the Paleogene. An important event, which marked the modern geological era, was the clash of India and Asia. Africa from the south-west "stuck" in Eurasia. Thus appeared the southern mountains of the Old World and Iran. Geological periods were slow, but the Earth map inexorably became similar to today's.
Ancient Ocean Tethys, separating northern Laurasiaand southern Gondwana, eventually disappeared. Today, only the seas (Mediterranean, Black and Caspian) remained from it. Important events also took place in the Southern Hemisphere. Antarctica broke away from Australia and headed toward the pole, turning into a glacial desert. There appeared the Panama Isthmus, which connected South and North America, finally dividing the Pacific and Atlantic oceans.
The first period that the moderngeological era, the Paleogene (66-23 million years ago). A new stage in the development of the organic world began. The boundary of the Mesozoic and Cenozoic was marked by the mass extinction of a huge number of species. Most people know this catastrophe for the disappearance of dinosaurs.
In place of the Mesozoic inhabitants of the Earth camenew mollusks, bony fishes and angiosperm vegetation. In previous geological periods on land, reptiles dominated. Now they have given way to the leading positions in mammals. Of the reptiles, only crocodiles, turtles, snakes, lizards and some other species have survived. The modern shape of amphibians was formed. The air was dominated by birds.
The common sequence of geological erassays that the second period of the Cenozoic era was the Neogene, which replaced the Paleogene and preceded the Quaternary period. It began 23 million years ago, and ended 1.65 million years ago.
At the end of the Neogene, the organic world is finallyadopted modern features. In the sea, discycyclines, assylins and nummulites became extinct. The composition of the organic world on land has changed dramatically. Mammals have adapted to life in the steppes, dense forests, semi-steppes and semi-deserts, thus colonizing vast territories. It was in the Neogene that they appeared proboscis, hoofed and other fauna (hyena, bears, martens, badgers, dogs, rhinoceroses, sheep, bulls, etc.) widespread today. Primates came out of the woods and settled in open spaces. 5 million years ago the first ancestors of a modern man from the genus of hominids appeared. Thermal-loving forms of flora (myrtle, laurel, palm trees) began to disappear in the northern latitudes.
Formation of modern mountains and seas
The process of mountain building continued in the Neogene,which determined the modern landscape of the planet. In America, the Cordilleras and the Appalachians were formed, in Africa - the Atlas. The mountains appeared in the east of Australia and in Hindustan. In the west of the Pacific Ocean appeared marginal seas (Japanese and Okhotsk). Active volcanoes differed, volcanic arcs rose from the water.
For some time the level of the World Ocean exceededModern, but by the end of the Neogene he fell again. Glaciation swept not only Antarctica, but also the Arctic. The climate became more unstable and contrasting, which was especially characteristic for the next Quaternary period.
Migration of fauna
In the Neogene period of the Northernhemispheres finally united in a holistic space. There was a Mediterranean way between Africa and Europe. The Turgai Sea disappeared in the West Siberian lowland. It separated Europe from Asia. After its drying, migration between different parts of the world was facilitated. Herbivorous horses came from America, and antelopes and bulls from Asia. Proboscis spread outside Africa. Cats, which at first were saber-toothed and lived only in America, flooded Eurasia.
4 million years ago, the Isthmus of Panama appeared. There was a land link between the two Americas, which led to an unprecedented hitherto migration of animals. The southern fauna throughout the entire Cenozoic was in isolation, actually upholstered on a huge island. Now, unfamiliar species came into contact. Fauna mixed. Battleships appeared in the north, sloths and marsupials. Horses, tapirs, hamsters, pigs, deer and camels (llamas) colonized South America. The northern animal world is enriched. But in South America there was a real catastrophe. Due to new competitors in the form of ungulates and predators, many rodents and marsupials died out. These contradictory events began to be called the Great American Exchange.
It took several billion years tonumerous geological eras and periods replaced each other and finally came to a point when the Quaternary period of the Cenozoic began a million and a half years ago. It continues to this day, so it can be considered modern.
All periods and eras of geological historydiffer from each other with unique features. Quaternary is also called anthropogen, since it was this period of time that the development and formation of man had to take place. His first ancestors appeared in East Africa. Then they settled Eurasia, and from modern Chukotka came to America. People have gone through several stages of development. The last (reasonable man) came 40 thousand years ago.
However, the Quaternary period is uniqueclimatic leaps. Over the last million years, several glacial periods have passed, changing for warming. The climatic conditions have led to the extinction of many heat-loving species of flora and fauna. Disappeared and animals that have adapted to life in the conditions of the glacial period (mammoths, woolly rhinoceroses, saber-toothed tigers).
The answer to the question, which era is now, is already found(the Cenozoic). At the same time, the Quaternary period continues today. It is also divided into parts. The modern department of the Quaternary period is the Holocene epoch. It began 12 thousand years ago. Scientists call it interglacial. That is, this is the period that has come after significant warming.
At the same time, modern mankindfind several small glacial periods. Climatic changes, characteristic of the whole Quaternary period, over the past 12 thousand years have been repeated several times. At the same time, they are miniaturized and not so much cardinal in scale. Climatologists note the small ice age, which occurred in 1450-1850. Winter temperatures in Europe fell, which led to frequent crop failures and shocks in the agrarian economy. A small glacial period was preceded by the Atlantic Optimum (900-1300). During this period, the climate was noticeably softer, and the glaciers decreased significantly. Here it should be remembered that the Vikings, who discovered Greenland in the Middle Ages, called it a "green country", although today it is not "green" at all.