Mass extinctions have occurred due to various reasons in different time periods of the world’s history. In these extinctions, many living species were wiped out from the scene of history. These mass extinctions in the world have been experienced in the form of events that affect the world in a short time, such as a meteor strike, as well as for long millions of years depending on atmospheric reasons. The five mass extinctions that have taken place in Earth’s history are as follows;
Permian – Triassic Extinction
Permian – Triassic extinction; It is also called “great death” or “great extinction”. It is estimated to have lived 251 million years ago. It is a mass extinction that initiates the transition between the Permian and Triassic geological periods, with the exception of the Paleozoic and Mesozoic periods. Known as the most severe extinction on Earth, this mass extinction wiped out 96 percent of all species. When the other is compared with extinctions; The extinction that affects even insects and takes the longest time for earthly life to recover.
Various theories have been put forward regarding the extinction, which is estimated to last for millions of years. According to the theories; The environmental changes that started to take place gradually and the disasters caused by the abundant meteorites hitting the earth were caused. Oxygen ratio in the seas has changed, sea level has regressed, volcanic eruptions have increased. With the coexistence of more than one of these events, global cooling has occurred. It is thought that all species surviving on Earth are descended from the 4% that survived the Permian-Triassic extinction.
Late Devonian Extinction
The Late Devonian extinction is estimated to have occurred 359 million years ago and wiped out two-thirds of all species on Earth. This extinction occurred not as a result of a single event, but after a series of disasters over millions of years. Life species in shallow seas were most affected by the extinction. Reefs and coral species disappeared until they emerged 100 million years later. Asteroid impacts, climate change and new types of plants mixed into the soil have brought about changes in sea level. For this reason, a large part of the sea bed was almost without oxygen and all living things, except bacteria, disappeared.
Cretaceous – Tertiary Extinction
Cretaceous – Tertiary extinction; It happened about 65 million years ago, and 75 percent of all living things on earth, including dinosaurs, disappeared. Although the cause of the disaster has not been fully proven, it is thought to be caused by a meteor falling on Mexico’s Yucatan Peninsula. The meteor hitting the peninsula is about 200 kilometers in diameter and 20 kilometers deep. Chicxulub Crater has created.
It is estimated that with the impact of the impact, great fires broke out, tsunamis were formed, and plenty of sulfur was emitted into the atmosphere, and therefore the climate changed radically. Climate change, which reached extreme dimensions, continued for many years and became the cause of mass extinction. Only some hibernating mammals and reptiles survived this extinction.
Ordovician – Silurian Extinction
Ordovician – Silurian extinction; It is the third largest extinction in world history. It is estimated that this extinction occurred 443 million years ago. During the Ordovician period, almost most of the life on earth lived in water. In the extinction blamed by the ice age, about 85 percent of marine life disappeared. A large ice sheet in the southern hemisphere caused climate change and a decrease in sea level, which led to extinction.
Triassic – Jurassic Extinction
There are two or three stages of extinction that created the Triassic-Jurassic extinction event. to extinctions in the Triassic period of 18 million years; It is thought to be caused by the effects of climate changes, flood disasters and asteroid impact. In this extinction, many marine reptiles, large amphibians, many living things that make up the reefs, and many mollusks were destroyed. About half of all species that lived at that time, when plants were also affected, disappeared.
