Mass extinctions: what are they, causes and what are they

To begin with, we must first know that the extinction of a species occurs when there are no specimens capable of reproducing and leaving offspring anywhere on planet Earth. Now, mass extinctions are one of the three types of extinctions that exist. Let’s see here how they are called and what are their differences:

• Background extinctions: they occur randomly in all groups of organisms and their loss occurs gradually.
• Mass extinctions: they cause a sharp decrease in the number of species that inhabit a certain geographic region and occurs over a certain period of time.
• Catastrophic mass extinctions: they happen instantaneously and on a global scale, as a result the biodiversity of species is drastically reduced.

In this other article you can learn more about the basic concept of species extinction: what it is, causes and consequences .

After reading the previous section, you may wonder why mass extinctions occur or what are the causes of mass extinction of species. There are multiple causes that lead to the disappearance of species, but below we will tell you some of them.

Biological causes

Here the characteristics of the species come into play and also the endemism and the competition that may exist between them. In this way, some species, especially invasive species in a territory, can displace other species, condemning them to extinction. In general, background extinctions occur due to these types of causes.

Environmental causes

Among the environmental causes are: changes in temperature, changes in sea ​​level , changes in biogeochemical cycles , movements of tectonic plates, among others. On this occasion, if the species cannot adapt to the new conditions of life, it is doomed to extinction. For its part, volcanic activity is also part of the environmental causes and, in general, these causes give rise to mass extinctions.

Extraterrestrial causes

We are not referring to Martians or UFOs, but rather to the impact of asteroids and meteorites on the surface of the Earth. In this particular case, extinctions occur during and after the impact since after the impact they can cause changes in the composition of the atmosphere, among other effects. Catastrophic mass extinctions, such as the extinction of the dinosaurs, are believed to occur from these types of causes.

Anthropogenic causes

They are those causes originated exclusively by the action of the human being. As an example, agricultural, mining, oil and forestry exploitation, environmental pollution, the introduction of exotic species, hunting and trafficking of wild species and also global warming are some of the environmental problems that humans have introduced into the ecosystems and that undoubtedly lead to the extinction of species.

Can you imagine how many mass extinctions have occurred throughout Earth’s history? There were certainly five mass extinctions. Many scientists even say that we are going through the sixth mass extinction . In this section we will tell you in which geological period each of the mass extinctions occurred, their duration and their causes.

Ordovician – Silurian extinctions

The first of the mass extinctions occurred approximately 444 million years ago. It is estimated that it lasted between 500 thousand to 1 million years and as a result more than 60% of the species became extinct. There are several theories about the causes that produced this extinction, the most forceful affirms that it was due to the explosion of a supernova that produced changes in the sea level and in the ozone layer.

Devonian – Carboniferous extinctions

It occurred approximately 360 million years ago and more than 70% of the species became extinct. This extinction event lasted 3 million years and is believed to have started with the eruption of a mantle plume or mantle plume, which are deep columns that come from under the earth’s crust and that originate hot spots and volcanic areas.

Permian – Triassic Extinctions

This event happened around 250 million years ago and lasted for a million years. As a balance, 95% of marine species and 70% of terrestrial species disappeared. The causes are not exactly known, but it is estimated that it may have been due to volcanic activity, the release of gases from the Earth’s core and an asteroid impact.

Triassic – Jurassic extinctions

260 million years ago this mass extinction event took place that lasted for a million years and wiped out 70% of the species. Among the theories that explain its causes are the fragmentation of the great Pangea continent and also successive volcanic eruptions .

Cretaceous extinctions – Tertiary

It happened 66 million years ago and is perhaps the most well-known mass extinction event, because the dinosaur species that inhabited the Earth became extinct in it. There are multiple theories that explain the causes, the main ones are based on high volcanic activity and the impact of a large asteroid. The curious thing about this event is that it not only killed the dinosaurs but also more than 70% of the species and it is estimated that it lasted only 30 days.

We recommend you read this other post from AgroCorrn about Why the dinosaurs became extinct . You can also get to know them a little better by reading these articles on Herbivorous Dinosaurs: Names, Types, Characteristics and Pictures and Carnivorous Dinosaurs: Names, Types, Characteristics and Pictures .

Holocene extinctions or the sixth mass extinction

This particular event generates numerous controversies, not only because it would be happening right now but also because its causes are merely anthropogenic. The truth is that since the development of human activities, the rate of extinction of species is on the rise and, for example, the rate of extinction of mammals is 280 times higher than normal rates. Furthermore, it is estimated that species extinct in the last two centuries (200 years) should have become extinct in 28,000 years. Given this, it is somewhat clearer that we are facing the sixth mass extinction of species.

To finish knowing these mass extinctions in the history of the planet, here below we leave you a time line of mass extinctions .

If you want to read more articles similar to Mass extinctions: what they are, causes and what they are , we recommend that you enter our Biology category .