What is a Mass Extinction? Are We in a Mass Extinction?

In the history of life on Earth, 99 per cent of all living things, approximately 4 billion species, have gone extinct. Older species dwindle away as new species adapt to fill ecological niches that are always changing. However, the pace of extinction is not steady. Millions of species were wiped off as a result of one of the five mass extinctions, including the most talked extinction of the dinosaurs. Seventy-five to ninety per cent of all species on Earth have vanished in a geological instant during what are known as mass extinctions, which have happened at least a few times in the past 500 million years.

What is Mass Extinction? Are We in Mass Extinction?
p/c nationalgeographic

A mass extinction is a biotic episode in geologic time in which a huge number of animal and plant species - roughly three-quarters vanish in a very short amount of time, probably between a few thousand and a few million years.

Mass extinction episodes are caused by a perfect storm of several catastrophes, such as the escalation of land temperatures and ocean acidification. While the exact causes of these occurrences are occasionally unknown, widespread volcanic activity is a common candidate. Theories that asteroid impacts cause major extinctions are still entirely hypothetical; only one space rock has been definitively connected to an extinction. Geoscientists have determined significant extinction events that occurred at the closing of several geologic periods based on evidence in the fossil record:

major mass extinction events, geologic time

Even though they are tragic occurrences, mass extinctions allow for the emergence of new life forms on the earth. The well-documented mass extinction, which occurred 66 million years ago and marked the transition between the Paleogene and Cretaceous, wiped out all non-avian dinosaurs and cleared the way for the rapid diversification and evolution of birds and mammals. Despite being the exception, the Cretaceous-Paleogene extinction is well known for being mostly brought on by a massive asteroid. The single most important trigger of mass extinctions seems to be major modifications to the carbon cycle on Earth, such as those caused by enormous volcanoes that erupted in igneous provinces and covered hundreds of thousands of square kilometers in lava. These eruptions spewed large volumes of heat-trapping gases into the atmosphere, allowing for runaway global warming and associated impacts like acidification of the oceans and anoxia, or a depletion of dissolved oxygen in the water.

Is the First Mass Extinction Primarily Caused by Volcanic Eruptions?

2nd Major Mass Extinction Event: Time, Causes and Facts

The Earth has been experiencing an additional extinction catastrophe that is swiftly wiping off mammalian life for the past 10,000 years. Humans are currently at the start of the most recent mass extinction, which is occurring considerably more quickly than any of the others. The International Union for the Conservation of Nature estimates that over 35,000 species are now endangered with extinction, with vertebrate species populations having plummeted by an average of 68% since 1970. According to a study that was published in the journal PNAS, as many as 543 terrestrial vertebrates went extinct during the twentieth century alone.

This serves as a succinct overview of mass extinction. Some recommended readings are:

Mass Extinctions and Their Aftermath, Mass Extinction Book

Carboniferous Giants and Mass Extinction, Mass Extinctions Book

A Brief History of Earth

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