Including the extinction of dinosaurs, there have been five mass extinctions on the earth. How many times do you know?

The earth has been born for about 4.6 billion years. Since the Phanerozoic era 540 million years ago, the earth has experienced five large-scale extinctions. People pay close attention to the causes of these extinctions.

But hundreds of millions of years of natural changes have almost wiped out all traces, leaving only a few evidences.

What are the real culprits of these five mass extinctions? Let’s do a general carding and analysis together with Xiaobian according to the time sequence.

The first mass extinction — Ordovician Silurian

Time: about 440-450 million years ago.

In this mass extinction, a large number of species of brachiopods, Bryozoa, conodonts, trilobites, bivalves and echinoderms disappeared, which can be said to be a disaster for marine invertebrates.

Only primitive fish survived and began to flourish after the mass extinction, gradually replacing invertebrates to dominate the ocean.

The possible causes are as follows

Some experts suspect that the event was caused by a gamma ray burst, which is an explosion in the universe.

At a distance of 6000 light-years away from the earth, a neutron star collided with the black hole for unknown reasons, producing several gamma ray bursts, one of which hit the earth impartially.

The destruction of the earth’s atmosphere led to the earth’s disintegration and the extinction of species.

In fact, the probability of gamma rays hitting the earth is very small, less than one in 100 million. If it is really because of this reason, we can only say that the creatures in that period were very unlucky.

The second mass extinction: Late Devonian

Time: about 375-350 million years ago.

Close to the Devonian Carboniferous transition period, this time is mainly due to the extinction of marine organisms, the extinction of gnarless fish, the extinction of pelagic fish, and the end of “fish age”.

The possible causes are as follows

Because of unknown reasons, the earth began to spray magma on a large scale, some fish were cooked, some fish were poisoned because of seawater pollution.

In the Middle Devonian, the plants were very prosperous, and the decaying matter of withered branches and leaves flowed into the sea along with the rain, which made the algae flourish unprecedentedly, consumed a lot of oxygen, and suffocated them.

As a result, the evolution of vertebrates and amphibians began to take over, and primitive plants began to emerge.

The third mass extinction Permian Triassic

Time: the transitional period from Permian to Triassic, 258 to 252 million years ago.

This is the largest of the five mass extinctions, with more than 96% of marine life and 70% of terrestrial life extincted.

The extinction almost brought the world back to the pre Phanerozoic era of single celled organisms, leading to a “dynastic change” in the terrestrial ecosystem, with the leader changing from synechoids (ancestors of mammals) to sauropods (reptiles, including dinosaurs).

The possible causes are as follows

The Siberian shield volcano has been erupting for hundreds of thousands of years, and methane hydrate exhalation in shallow water has led to greenhouse effect, frequent acid rain and ocean hypoxia.

The fourth mass extinction — Triassic Jurassic

Time: about 200 million years ago.

More than 75% of the animals died out. Strangely enough, dinosaurs survived the mass extinction and became the absolute king of the Jurassic era, which lasted nearly 140 million years.

Some of the fish and marine reptiles were extinct, and some of the ancient fish populations began to change to the present population. Sharks in the modern sense appeared after the mass extinction.

The possible causes are as follows

At the end of the Triassic, a super volcano erupted in the Middle Atlantic, and the magma spewed out covered an area of 7 million square kilometers, equivalent to the area of the whole Europe.

The fifth mass extinction: Cretaceous tertiary extinction event

Time: about 65 million years ago.

More than 75% of the species are extinct, including the most familiar dinosaurs. However, this extinction has led to the rise of mammals, which is the least serious of the five mass extinctions and the most well-known one.

The possible causes are as follows

The main cause of this extinction is asteroid impact, and the evidence is KT line sediments and the crater of Yucatan Peninsula in Mexico.

This is the event of five mass extinctions. Some researchers said that due to the earth’s population explosion, environmental pollution and other reasons, the earth is likely to have “the sixth mass extinction of species”.

And the cause of extinction is precisely because of human activities. Therefore, if we do not pay attention to and take good care of the earth, it will cause irreparable consequences.

What do you think of this? Welcome to comment area.

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