Great Perm species extinction: possible causes

Permian extinction became one of the biggest catastrophes that happened during the long history of the Earth. The biosphere of the planet has lost almost all marine animals and more than 70% of terrestrial representatives. Did scientists understand the causes of extinction and assess its consequences? What are theories put forward and can they be trusted?

The Perm period

To approximate the sequence of such far-off events, it is necessary to turn to the geochronological scale. Total Paleozoic consists of 6 periods. Perm is a period on the border of the Paleozoic and Mesozoic. Its duration on the geochronological scale is 47 million years (from 298 to 251 million years ago). Both eras, both Paleozoic and Mesozoic, are part of the Phanerozoic eon.

Each period of the Paleozoic era is interesting in its own way and rich in events. In the Permian period there was an evolutionary push, which developed new forms of life, and the Permian extinction of species, which destroyed most of the animals of the Earth.

What is the name of the period

"Perm" is a surprisingly familiar name, do not you think? Yes, you are not mistaken, it has Russian roots. The fact is that in 1841 a tectonic structure corresponding to this period of the Paleozoic era was discovered. The find was located near the city of Perm. And the entire tectonic structure today is called the Predural edge trough.

The concept of mass extinction

The concept of mass extinction is introduced into scientific circulation by scientists of the University of Chicago. The work was carried out by D. Sepkoski and D. Raup. According to statistical analysis, 5 mass extinctions and almost 20 catastrophes of a smaller scale were identified. It took to review the information for the last 540 Ma, since earlier data periods are not enough.

The largest extinctions are:

• Ordovician-Silurian;
• Devonian;
• Perm species extinction (the reasons for which we are considering);
• Triassic;
• Chalk-paleogene.

All these events occurred in the Paleozoic, Mesozoic and Cenozoic eras. Their periodicity is from 26 to 30 million years, but many scientists do not accept the established frequency.

The Greatest Ecological Catastrophe

Perm's extinction is the most massive catastrophe in the history of our planet. Marine fauna has died out almost completely, terrestrial species preserved only 17% of the total. More than 80% of insect species have died out, which did not happen during other mass extinctions. All these losses happened in about 60 thousand years, although some scientists suggest that the period of mass moras lasted about 100 thousand years. Global losses, which brought great Permian extinction, had a final feature - crossing it, the Earth's biosphere began to evolve.

The restoration of the fauna after the greatest ecological catastrophe lasted very long. It can be said that much longer than after other mass extinctions. Scientists are trying to recreate models for which a mass sea could flow, but so far they can not even converge in the number of jerks within the process itself. Some scientists believe that the Great Permian extinction 250 million years ago had 3 peak jolts, other scientific schools are inclined to the fact that there were 8.

One of the new theories

According to the scientists, the Permian extinction was preceded by another mass catastrophe. It happened 8 million years before the main event and significantly undermined the Earth's ecosystem. The animal world became vulnerable, so the second extinction within one period was the greatest tragedy. If it is possible to prove that there were two extinctions in the Permian period, then the concept of the periodicity of mass catastrophes will be doubted. For the sake of justice, let us clarify that this concept is disputed from many positions, even without taking into account the possible additional extinction. But this point of view still holds scientific positions.

Possible causes of the Permian disaster

Permian extinction still causes a lot of controversy. Acute controversy unfolds around the causes of environmental cataclysm. As equivalent, all possible grounds are considered, including:

• External and internal catastrophic events;
• Gradual changes in the environment.

Let's try to consider some components of both positions in more detail in order to understand how great the probability of their influence on the Permian extinction. Scientists of many universities provide photos of confirming or refuting findings as they study the issue.

Catastrophe as a cause of Permian extinction

External and internal catastrophic events are considered to be the most probable causes of the Great Extinction:

1. During this period, there was a significant increase in the activity of volcanoes on the territory of modern Siberia, which led to a large outpouring of the trap. This means that a huge eruption of basalt occurred during a short time in the geological term. Basalt is slightly prone to erosion, and the surrounding sedimentary rocks are easily destroyed. As evidence of trap magmatism, scientists cite huge territories in the form of flat stepped plains on a basalt base. The largest trap area is the Siberian trap, formed at the end of the Permian period. Its area is more than 2 million km². Scientists of the Nanking Institute of Geology (China) conducted a study of the isotope composition of the Siberian Trap rocks and established that the Permian extinction occurred precisely during their formation. It took no more than 100 thousand years (before that it was believed that it took a longer period of time - about 1 million years). The activity of volcanoes could provoke a greenhouse effect, volcanic winter and other processes, destructive for the biosphere.
2. The causes of the biospheric disaster could be the fall of one or several meteorites, the collision of the planet with a large asteroid. As a proof, a crater with an area of more than 500 km (Wilkes Land, Antarctica) is given. Also evidence of shock events found in Australia (Bedouht structure, Northeast of the continent). Many of the samples were later disproved in the process of a deeper study.
3. One of the possible reasons is the sharp release of methane from the bottom of the seas, which could lead to total death of marine species of animals.
4. The catastrophe could result in the production by one of the domains of living unicellular organisms (archaea) of the ability to process organic matter, releasing large volumes of methane.

Gradual changes in the environment

There are several points in this category of reasons:

1. Gradual changes in the composition of sea water and the atmosphere, resulting in anoxia (lack of oxygen).
2. An increase in the dryness of the Earth's climate - the animal world could not adapt to the changes.
3. The consequence of climate change was the disturbance of ocean currents and a decrease in sea level.

Most likely, the whole complex of reasons has affected, since the catastrophe was of a massive nature, and occurred in a short period.

Consequences of the Great Extinction

The great Permian extinction, whose causes are trying to establish a scholarly world, had serious consequences. Entire units and classes have completely disappeared. Extinction of most of the parareptilis (left only the ancestors of modern turtles). A huge number of species of arthropods and fish disappeared. The composition of microorganisms has changed. In fact, the planet was emptied, being in the power of fungi, eating carrion.

After the Permian extinction species that were maximally adapted to overheating, low oxygen levels, lack of food and excessive sulfur content survived.

Mass biosphere cataclysm opened the way for new species of animals. Trias, the first period of the Mesozoic era, showed the world archosaurs (the progenitors of dinosaurs, crocodiles and birds). After the Great Extinction on Earth, the first species of mammals appeared. The restoration of the biosphere took 5 to 30 million years.