In the history of earthly life, scientists have counted up to 11 mass extinctions of flora and fauna, 5 of which have greatly changed the face of our biosphere. The last of these “Great” extinctions that occurred 65 million years ago, destroyed one sixth of all the then existing species (Cretaceous-Paleogene extinction). At the same time, together with the sea and flying lizards, the most “propiarist” group of animals in the fossil record of our world disappeared - all dinosaurs.

Modern science does not have comprehensive data on the causes of the last major extinction of species (as well as the previous ones). Asteroids, volcanoes and internal processes in the earth’s biosphere are among the main suspects. Below, I suggest that you familiarize yourself with the 300 million-year-old chronicle of earthly catastrophes and form your own opinion about the causes of the death of this remarkable squad of reptiles.

"Mother of all extinctions"

250 million years ago, the largest known extinction occurred in the history of our planet, during the Permian-Triassic catastrophe, 95% of all species of marine and land animals died. Almost all the therapies then dominating on land disappeared. Among the few surviving terapids were the ancestors of cynodonts, whose descendants are all mammals.
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The animal-like lizards (synapses) include Early Permian pelicosaurs (on the left is dimetrodon) and their descendants therapsid (on the right is the gorgonops). In particular, gorgonops are close relatives of cynodonts.


The vacated ecological niches of the Therapsids were occupied by the Archosaurs, which already after 20 million years will begin to dominate as land predators (dinosaurs and Krootarses).

The main cause of this extinction is usually considered the outpouring of magmatic Siberian traps on the border of the Permian and Triassic periods. During the formation of the trap, about 4 million km3 of rocks were thrown out, covering an area of ​​2 million km2. The outpouring of rocks has triggered a cascade of global climate change as a result, presumably causing mass extinction.

The area of ​​the eruption of the Siberian trap on the map of modern Russia

"Mysterious" Triassic-Jurassic extinction

After 50 million years, the terrestrial biosphere had to face another series of mass extinctions. At the border of the Triassic and Jurassic periods, an unknown global cataclysm found the mainland crutches onshore. Having displaced their "cousins" of dinosaurs and mammals, the krotrotarses by that time became the main and largest land predators of the late Triassic.

Some representatives of the Late Triassic carnivorous predatory


As a result of the catastrophe, krotroarza shared the fate of the Therapsids, giving way to their “cousins” - dinosaurs who will dominate on land for a long 140 million years. One of the two surviving groups of Krootroffs, the protogamous, are the direct ancestors of modern crocodiles.

The main versions of this extinction are the fall of a large asteroid and volcanic activity (Central Atlantic Magmatic Province, TsAMP). In the first case, the impact was considered to be a 4 km long asteroid, which formed the 100 km crater Manikuagan in Canada, but geological dating refers to its fall by 14 million years before the Triassic extinction.

Today, the Manikuagan crater has a transverse diameter of 70 km (initially 100km). Craters of this size usually appear when asteroids are about 4–5 km in diameter, and do not have long-term consequences for the Earth’s fauna and flora.


The greatest support received the combined hypothesis. According to her, the CAMP, which caused the outpouring of 2 million km3 of volcanic rock, including a huge amount of CO2, provoked through global warming the release of huge bottom oceanic pockets of methane hydrates. Methane, being a stronger greenhouse gas than CO2, launched a chain reaction to overheat the earth's atmosphere, which, presumably, caused massive extinctions.

"Stable" Mesozoic

The period of dinosaur domination on land (the Jurassic and Cretaceous periods of the Mesozoic era) was not at all geologically “quieter” than the other periods of Earth history.
183 million years ago, a large magmatic outpouring of the Karu-Ferar occurred, comparable in scale to TsAMP (2.5 million km3 of igneous rocks). However, this event did not cause however catastrophic consequences for earthly life. A major asteroid with a diameter of about 4 km 167 million years ago - in the middle of the Jurassic period (destroyed by the Puchezh-Katunsky crater in the Nizhny Novgorod region of Russia) passed without serious consequences.

The second mass extinction in the history of dinosaurs occurred on the border of the Jurassic and Cretaceous periods - 145 million years ago. One of many hypotheses links with this “small Jurassic” extinction the formation of one of the largest shield volcanoes of the solar system - the Tamu massif in the Pacific Ocean. However, it is possible that the global effect of the formation of the volcano increased the impact of 4 km of the asteroid in the same period of time ( Morocweng Crater , South Africa). By this time, scientists attribute the appearance of flying dinosaurs - the ancestors of modern birds.

The Tamu massif in the Pacific is one of the largest extinct volcanoes in the solar system. The total mass of the rocks composing this ancient volcano is 80% of the mass of the Martian Mount Olympus


Approximately 12 million years later, already at the beginning of the Cretaceous, the world's flora and fauna experienced a series of the largest explosive volcanic eruptions in Earth history. An eruption at the beginning of the Goterivian stage of the Cretaceous period of 8 super-volcanoes released 50,000 km3 of gases and rocks. Thus, the eruption of each supervolcano was, on average, twice the strength of the eruption of the supervolcano Toba, 70,000 years ago, which caused the bottle neck effect .

The fact is remarkable also by the fact that the “parade” of supervolcanoes was only part of the formation of the giant igneous tracts of Parana Etendek in South America. The total volume of released rocks was 2.3 million km3. However, as well as 50 million years earlier, these processes did not cause significant fluctuations in the diversity of the terrestrial biosphere.

Crests formed by basalt streams of ancient magmatic trappes of Paraná, Brazil


By the end of its era, dinosaurs experienced another 3 major peaks of volcanic activity, in total, spewing 12 million km3 of rocks. During the Cretaceous, the Earth also experienced a series of collisions with large asteroids (3 asteroids 1 km in diameter, three more each 2 km, and one 3 km in size).

The largest (after Chicxulub) impact crater of the Cretaceous period - Karsky is located in the Nenets Autonomous District of Russia. The impact of a 3 km asteroid of 70 Ma for Nazat formed a crater with a diameter of about 70 km. The beginning of the decline in dinosaur speciation is attributed to the same period, although the connection between these two events is the subject of discussion.

The end of eternity

If we could get to the end of the Cretaceous period, many of us would not have believed that we got into the ancient and alien world. Angiosperms (flowers) dominated everywhere, with mammals that were little different from modern, not large animals. They have already managed to divide into placentals and marsupials. At the same time lived the first primates. Snakes and familiar lizards appeared. From the Jurassic period, the forests were teeming with real birds, and their relatives crocodiles ambushed the animals that came to the river.

Bees are also considered partly responsible for reducing dinosaur diversity in the Late Chalk. Having evolved about 100 million years ago from the wasps that fed on insect pollinators, bees, thanks to their high efficiency, made flowering plants dominant in the earth's flora. Herbivorous dinosaurs, not without difficulties, had to slowly change the diet from gymnosperms to flowering plants


The similarities of our world with that ancient one are limited to the composition of the fauna at the mental watering, most of which were still dinosaurs: tyrannosaurs, ceratops, hadrosaurs, sauropods, etc. (a more detailed list of the fauna of the end of the dinosaur era).
By the end of the era of domination of the dinosaurs, on the border of the Cretaceous and Paleogenic periods, volcanic activity in India (then an island in the middle of the Indian Ocean) increased. The amount of outpouring of the Dekanskiy trap over several hundred thousand years was about 2 million km3, the peak occurred at the lava eruption of the Mahabaleshwar – Rajahmundry trap, when during a short (geologically) period the emissions amounted to 9 thousand km3 of rocks.

Dekan Trapps near Mumbai and the area of ​​India they occupy (in blue)


However, according to previous precedents of colossal volcanic activity, we already know that such phenomena themselves do not necessarily have a catastrophic effect on the Earth’s climate, and, accordingly, flora and fauna. Most likely, such activity should coincide with exceptional circumstances in order to launch the “mechanism” of mass extinction.

Only 6 of 11 major extinctions coincided in time with active geological processes. Most modern paleontologists hold the opinion that such an “exceptional circumstance” was the impact of a 10 km asteroid in central America 65 million years ago, during the active phase of the formation of the Dekan Trapp.

Impact power was unprecedented in the history of the Mesozoic era. The released energy was 2 million times higher than the energy of the explosion of the largest thermonuclear charge - “King of the bomb”. The area of ​​the 180 km long Chicksul crater was comparable to the total area of ​​all impact craters formed in the previous 200 million years.

According to some geological models, the seismic wave from the explosion could be focused at the antipode point of the impact crater and cause lava eruptions (or amplify them). By the way, at the antipode point of the collision, then there was a region of increased volcanic activity - the very Dekansky trap. The hypothesis does not at all assert that volcanism was triggered by the impact of an asteroid, since the formation of the trapp data was a purely autonomous process of the earth's lithosphere. We are talking exclusively about the possible short-term intensification of volcanic activity, since the phenomenon of "seismic focusing" in the particular case of the Earth is very limited .

Crater Chiculub on the Yucatan Peninsula (Mexico). On the left - a crater in the visible range, on the right - with a superimposed map of gravitational anomalies


Another important condition for the beginning of the process of mass extinction is the state of flora and fauna at the time of "force majeure". As before the Permian-Triassic extinction, paleontologists fix a decline in the diversity of dinosaurs and other archosaurs in the Maastrichian tier of the Late Cretaceous (last 7 million years of existence of dinosaurs). This is attributed to global climate change, since the reduction in diversity has extended to many other groups of animals and plants (including mammals, birds, and flowering). This gave rise to many paleontologists to suggest that these two catastrophic events (volcanoes and an asteroid) occurred at a time “inconvenient” for the living fauna.

Graph of the frequency of igneous eruptions (scale on the right) and asteroid strikes (scale on the left) for the last 300 million years (from confirmed). The former have a relatively long-lasting effect on climate (millions of years), the impact of asteroids is “experienced” by nature for several tens of thousands of years. As you can see, natural disasters do not always provoke mass extinctions (red dots at the top - major extinctions, black ones - small ones)


The schedule of "short-term" volcanic eruptions for the post-140 million years. Unlike explosive, lava eruptions are not accompanied by significant explosive secretions of molten rock. The eruption process is relatively quiet. The red circle indicates the eruption of supervolcano Toba, 70 thousand years ago.

"The Great Fracture"

The last of the major extinctions and the fourth for mammals occurred at the border of the Eocene and Oligocene epochs of the Paleogene period 35-30 million years ago. The percentage of species extinction is several times higher than the “background” level - more than 3% versus 0.7% (an order of magnitude weaker than Cretaceous extinction). This is the longest of all extinctions of the last 300 million years, lasted 4 million years. Eocene-Oligocene extinction is associated with both the fall of two large asteroids 35 million years ago (~ 5 and ~ 4 km in diameter, respectively), and significant global volcanic activity 35-29 million years ago (Northern, Central and South America, Africa and Middle East, see chart above).

100 and 90 km craters Popigay (Russia) and Chesapeake (USA), formed with a small time interval of 35 million years ago, and presumably became one of the causes of the Eocene-Oligocene extinction and general cooling of the climate in the Oligocene

"Leviathans"

However, according to many modern biologists, the Eocene-Oligocene extinction was not the last. From the last ice age, 11,000 years ago, the Earth’s biosphere began to experience another “Great Extinction” in its history ( Holocene extinction ). It has already exceeded the scale of the Eocene extinction, and according to scientists' estimates, the species diversity of the fauna of our planet is reduced by 50% already at the end of this century (more than 80% for the Earth’s flora). And the cause is not volcanoes or asteroids at all, but the emergence and development of a very unusual kind of animals - reasonable man.

As can be seen in the illustration below, the appearance of man most often provokes a sharp decline in the number of large mammals (Megafauna). In Africa and South Asia, the effect was weaker, as the fauna gradually adapted to coexistence with human species gradually replacing each other. On the rest of the continents, where the appearance of the “super hunter” was relatively sharp, the effect of the reduction was much more significant.


Unfortunately, we often forget that the intellectual superiority of man over the rest of wildlife should be accompanied by a great responsibility, rather than predatory and often irrational plunder and destruction of its benefits. Let us hope that the matter will not reach the “ Great Anthropogenic Extinction, ” and if it does, we will not disappear into the same abyss into which we will sweep away most of the terrestrial biosphere ...

Well, dinosaurs continue to be part of the Earth’s fauna in the form of evolutionarily successful birds. The relationship of birds with dinosaurs, their differences and similarities will be discussed in the next review.