style="font-size:15px;"> Titanosaurus. Art object, reconstruction
The Jurassic period (named after the Jura mountains in Switzerland) is characterized by clastic rocks (sharp stones), shales (layered accretion of minerals), igneous rocks (basalt is a loose gray stone with crystalline inclusions), clays and sands. All this is evidence of the disintegration of Pangea into continental blocks, with the accompanying formation of many shallow warm seas. Treelike ferns with branches lying in one plane, forming a semblance of a leaf, and also, similar to palm trees, but less lush 10—18 meter cycads, are spreading. Reef communities (simply reefs) are formed from coral polyps formed in the Triassic.
Archeopteryx appears – an «ancient bird» the size of a crow, clumsily, according to paleontologists, planning from tree to tree. Actually, the scientific community still does not have a generally accepted theory of the origin of birds. It is in the Jurassic that pterosaurs, flying warm-blooded lizards, conquer the air. A well-known representative of this genus, the pterodactyl suborder – pteranodon has a wingspan of considerable 7 meters. Also known are their big brothers, found in North America quetzalcoatl, 12 m wide, which corresponds to the dimensions of a light bomber during the Second World War.
The Cretaceous Period (Cretaceous), which began 145 million years ago, is characterized by abundant deposits of correspondingly writing chalk. What students use to draw signs on the board from the remains of funny invertebrate marine animals – ammonites, is formed. Vast tracts of land diverge, forming bodies of water, warm shoals and islands. Flowering plants appear, they are angiosperms, with a flower as a reproductive organ and complex double fertilization.
This is extremely pleasing to insects, which become the main pollinators of plants. Their diversity is increasing dramatically. Mesozoic landscapes flourish
In the sky, together with pterodactyls that look like huge bats, real, that is, feathered birds, already fly.
All this idyll ends 65 million years ago, during the Cretaceous-Paleogene great extinction, which was most studied by scientists.
Chicxulub crater
The main version is the fall of a celestial body, which caused the appearance of the Chicxulub crater near the Yucatan Peninsula (Mexico). The diameter of the killer asteroid is 10 kilometers, the depth of the crater is 17—20 km. width 180 km. The impact force is 2 million times greater than the energy released during the testing of the most powerful hydrogen bomb AN 602 on Novaya Zemlya.
Perhaps this impact was reinforced by the fall of a second celestial body, an asteroid or comet. Evidence of this emergency is the oval crater Shiva off the coast of modern India, 400 kilometers in diameter at its narrowest part. The fact is that, apparently, after the first outbreak of extinction, some species of dinosaurs have existed for another one or two million years.
As a consequence, chalk deposits are separated from the rocks of the next period by a layer of gray clay, sand and lime.
New era – Cenozoic («new life»). It starts from the Paleogene. This geological period is distinguished by a fairly even tropical climate, the dominance of mammals, birds, the first cetaceans, as well as teleost fish. Some cephalopods get rid of shells and turn into octopuses, cuttlefish and squid known to us.
Mesonychium, ancestor of whales
Neogene opens 23 million years ago. Whales are taking shape. Their basis is the mesonychia, extinct 63 – 28 million years ago, one of the few predators among ungulates. They resemble a wolf, bear and lion at the same time.
…Placentals, ie, viviparous mammals dominate. The fauna of the period is already clearly similar to the modern one.
The Quaternary period, he is also an anthropogen («creating man») starts 2,588 million years ago. It is separated from the previous epoch by the Gauss-Matuyama paleomagnetic boundary. The north and south magnetic poles of the Earth are reversed. The first era – the Pleistocene (from the Greek «numerous» and «modern») – the time of glaciations and interglacial periods, ends only 11.7 thousand years ago. Here, look, you are surrounded by woolly rhinos, saber-toothed tigers, cave lions, marsupial lions, mammoths and diprotodons (something like marsupial grizzlies), mastodons (simplified – short-haired mammoths with a special structure of jaws). Severe cold snaps, during which glaciers occupy 30% of the land area, last on average 40 thousand years. They are replaced by 20 thousand-year interglacials.
Wurm glaciation
The last ice age, that is, the Wurm glaciation, starts 110 thousand years ago. A stunning ice sheet spreads across Eurasia from Norway. The covers of Antarctica are being formed. The last glacial maximum ends 11 thousand years from our time with you. The level of the World Ocean rises by 120—135 m. It seems that everything is fine.
Why did the fossil nowadays warm-blooded animals, adapted to many perturbations, become extinct? The main reason, so beloved by scientists, is still the same – the fall of an asteroid on the territory of present-day Canada or Mexico and the associated sharp, within one day, global, simply violent cooling. Mammoths freeze while standing, not even having time to digest food.
Be that as it may, the main time is dominated by the Holocene («whole» and «new»), the interglacial period, which continues to this day, is relatively favorable for our life.
Man stands out from the animal world three million years ago, in the Paleolithic, roughly coinciding with the Pleistocene. People practically indistinguishable from modern Homo sapiens formed 35—40 thousand years before us. These figures are controversial, but we can present them as the basis for all subsequent calculations. Skills – making ceramics, fishing, hunting, and other tools from bone, leather, wood.
The first religious rituals appear.
Stone, Bronze, Iron Age
Child of the Stone Age. Historical reconstruction
The late Holocene is marked by the wide strides of Homo sapiens. The first of them – the Neolithic or Stone Age – lasts from the beginning of the Pleistocene. It is preceded by the Mesolithic, when people accumulate the skills of joint hunting, improve their speech, develop an understanding of social norms, religious prohibitions, and long-term traditions.
Modern scholars advertise the first pronounced archaeological culture – the so-called. «Hamburg», which suddenly appeared on the territory of the modern Netherlands and Germany. It is evidenced by stone spearheads with a lateral recess and stone incisors. The oldest city on Earth mentioned in the annals is Jericho (in Arabic – «Ariha», Greek – «Jericho», located now on the territory of the Palestinian National Authority, 30 km north-west of Jerusalem.
Neolithic people
About 6, 5 thousand years ago, mankind passes into the Bronze Age (in America, it is rather copper-obsidian). By the 13th century BC, the era of human development, characterized by the general peaceful coexistence of tribes, for better or worse, ends. Sources
