6 Mass Extinctions

There is a growing school of scientific thought that the Earth is in the middle of the sixth great extinction event in its history. A mass extinction event refers to a period when an abnormally large number of animal species simultaneously die out over a time frame much shorter than that which could account for the ‘natural’ rate of extinction through the process of evolution, which refers to the process by which older species are replaced by newer variations which inhabit ecological niches. A mass extinction event can, therefore, take place over hundreds, thousands or millions of years, as in terms of evolutionary history such timeframes are minute.

Mass extinction events are caused by drastic changes to the conditions on the planet, which can occur for a number of reasons, from alterations to the atmosphere and volcanic activity to asteroids smashing into the surface. Through fossil records scientists have identified five previous mass extinction events in the history of the Earth.

First
The first mass extinction took place at the end of the Ordovician age. This was approximately 440 million years ago. At that time most animal species lived in the sea. Massive glaciations occurred which locked up most of the water on the planet. This caused sea levels to drop precipitously. It is thought that as much as 60 percent of animal species on Earth perished during the Ordovician mass extinction.

Second
The second mass extinction event occurred over a period of around 20 million years, starting about 360 million years ago, during the later stages of the Devonian age. Successive glaciations meant that approximately 70 percent of all marine species were wiped out, particularly in the shallow areas of the seas. This is where coral reefs live and coral didn’t return to much of the ocean until over 100 million years later when a new species evolved. Insect and some formative amphibian animals had by this time inhabited the land, and many species of these terrestrial creatures were made extinct as well during this time.

Third
The third extinction is the most devastating in the planet’s history – as many as 96 percent of all animal species died out during it, across the board, from terrestrial vertebrates to marine animals and insects. It is for this reason that the event is often referred to as ‘The Great Dying’. This event took place at the end of the Permian age, around 225 million years ago. The cause of the third extinction is not known for certain, but it thought that either a comet struck the Earth or massive volcanic activity unsettled the surface of the Earth, causing a sudden release of methane from the sea floor, which would have triggered massive climate change. The likelihood is that all played a part, causing a number of ‘pulses’ of extinction events during this period. All life currently on Earth is descended from the 4 percent of species that survived this extinction.

Fourth
Around half of all marine invertebrates as well as many land animals, especially amphibians, were wiped out during the fourth mass extinction event, which took place over approximately 18 million years at the end of the Triassic age, beginning 200 million years ago. As with the third event, the likeliest causes are volcanic activity or a comet or asteroid hitting the Earth. About half of all animal species on the planet were wiped out by this event, including not only the dinosaurs but also marine reptiles and many plant species. Mammals were less affected, and this extinction event provided the historical niche through which the mammals, and eventually humans, came to dominate the planet.

Fifth
The fifth mass extinction event is arguably the one most people are aware of, as it was during this time that the dinosaurs all became extinct. Occurring about 65 million years ago, a massive asteroid hit the planet (it is thought that a crater found off Mexico’s Yucatan Peninsula shows the point of impact), triggering huge changes in temperature, sea levels and altering the chemical makeup of the atmosphere. It is thought that global temperatures were caused to rise 10 degrees higher than they are today, while the oceans were thought to have risen by as much as 300 meters in comparison to today’s levels. This would have meant as much as 40 percent of the land mass that is currently above sea level would have been submerged.

Sixth?
The notion that we are currently in the midst of a sixth mass extinction event is a sobering one, particularly as we, humans, are the cause of mass extinctionit. It is not simply something that is happening now; the sixth extinction takes in much of human history. We have been responsible for the extinction of single species by our own hands, such as the hunting of mastodons to extinction by our ancestors, or the willful destruction of the carrier pigeon, but the rate at which humans have killed off animal species has increased exponentially as we have become more industrialized as a society. As international travel became possible we transported – inadvertently or deliberately – invasive species from one part of the world to another that wiped out native animals. Diseases that had not previously been active on one continent were bought by travelers and decimated wildlife. Modern chemicals have poisoned seas, killing coral reef species and causing the fish species that depend on them to decline dramatically. And as the global human population has grown the pressure on natural resources of food has become intense, so that many species, particularly of fish, are now close to extinction. And then there is climate change. The pollution caused by the burning of fossil fuels is changing the atmosphere if the planet, causing extreme weather events, increased temperatures, rising sea levels and fundamental changes to the make up of the planet. This will have catastrophic effects on animal species, but also, unless a radical shift in attitude and process occurs, could well cause the downfall of the human race eventually as well.

31 comments

I’m not sure if most people would want to hear this, or believe it, but the facts are there. What remains is that we find a way to preserve what life is left. I think if we find groups within our own communities and set out to do things locally that will help the envionment that is where we need to start. I think we need the courage to accept what we have done and move on to preserve the planet. If we do this and it turns out it is too late, at least we did what was right in the end.

Show biz! Right Greg Foss?

Reading The Sixth Extinction by Elizabeth Kolbert – An Unnatural History – Very good read –

Hey I know – let’s use our food as fuel.

being able to put your head between your knees helps too

oh yeah i almost forgot….ehhhem evolution leads to extinction…creation leads to everlasting life.

Hey, Check out who is watching your profile=-> 🙂 http://facebook.com/10203047118250108?

how very sad for humanity 🙁

Very intense… Would better PAUSE most actual systems and make a maintenance to responsabilize them all and to correct those systems’s impact in order to let these be nocive no more…

We are already well into the second mass extinction event we have created.

The Hopi know !

Yepp
and soon well be bones to

NONE of the creatures in the previous 5 extinctions had the choice as to whether they should and then could prevent it. This time, one of the species can understand and choose their actions, but they’re really really slow off the mark! We’re talking “Stellar Level Morons From Earth”.

How were there any mass extinctions before man was burning fossil fuels to cause climate change? Oh, that’s right – it’s a natural process.

Thank you Jeff. Climate change is the biggest rip off in politics.. There is no harm to earth when a species dies as many have since the earth began.

Stupid is as stupid does.

It will be our turn at some point.

One logical choice sentient beings have is to commit suicide.

Climate changes every day, nothing you do or say will stop it. After Al Gore changed the name he has no authentic clame to anything, except your money he stole.

OH NO THE SKY IS FALLING ! LIBTARDS

I’m not a big Al Gore fan but how he get our money. I keep hearing people say he took our money. I miss that part. Somebody please enlighten me. Y’all seem to be real smart people. LOL

It is also caused by man killing them systematically.

Boy I sure wish we still had trillobytes, they probably tase like lobster?

THANKS TO ANN, ZACHARY and ERIC…worrisome

John Gemel interesting theory!

We’re well on our way, faster than most of these by far. We’re number one!

When we cause the oceans to die the ripple effect will spread across the terrestrial zones and the human species will die as well.
Rising oceans, depleted ozone, and higher concentrations of carbon may impact the earth but the pollution and decimation of the oceans ecosystems fragile food webs will eventua lot cause a cataclysmic failure of vital systems that once started will exponentially spread and cause massive extinctions sending the earth into a major evolutionary adjustment that in turn will cause Desease, starvation, oxygen depletion, and a huge rise in carbon dioxide through decomposition. The humans species may survive this epoch event and the earth will survive and life will find a way to mutate and adapt to the harsh atmosphere. In time, millions of years, the atmosphere may recover to something similar to what we enjoy today or it may morph into something completely different.
The question and answer is why? When we are intelligent enough to foresee and prevent these events. As the stewards of our planet; Will we allow narcissist greed and wanton cognitive destruction of the Earth’s Kingdoms to prevail as is the current course or will we learn to respect and love each other and all the beautiful species, geological features, and phenomenon here today. Kirk L. Foyle
03/29/2018. #KLF

Mike Borrelli 6

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