Seven of Earth's Mass Extinction Events

Modern Sea Pen
Modern Sea Pen

The Precambrian and Vendian Mass Extinctions

Our first mass extinction took place 650 million years ago when all the animals in the world lived in the sea. It claimed 70% of the oceans dominant creatures. A second mass extinction took place at the end of the Vendian and unlike the previous event did not take the hard-bodied animals so much as the soft bodied one, the ancestors of jellyfish, segmented marine worms, and sea pens. These modern animals jellyfish, segmented marine worms, and sea pens exist today because of an evolutionary boom that made all the surviving animals make up for lost time. Scientists believe this extinction may have been caused by the forming of glaciers for the first time in earth’s history since the evolution of life. This was such a large event that almost no microorganisms survived.

The fossilized shell of a brachipod.
The fossilized shell of a brachipod.

The Ordovician Extinction

The Ordovician Extinction happened 434 million years ago and claimed up to 85% of all marine life. There wasn’t any land based life forms yet to decimate. Considered the second most deadly extinction to marine life forms it took with it over 100 families of animals with it. Reef building animals took a hard blow and so did all the animals that lived in those reefs. Brachipods which were one of the most prolific and dominant life forms lost a third of their species. Conodonts, acritarchs, bryozoans, and trilobites suffered similar percentages of losses. This extinction was separated by two events one million years apart from each other.

The first part may have been caused by the earth’s temperature cooling down at a rate they could not evolve to keep up with. The second phase seems to be because the formation of glaciers made the sea levels go down.

The skull of a placoderm.
The skull of a placoderm.

The Cambrian and Devonian Mass Extinction

The Cambrian mass extinction was actually a combination of four smaller extinction events that spanned 408-360 million years ago. It claimed most of the species we had come to know and love in the fossil record like trilobites. It is thought to have killed off over 100 families of marine animals and striking a catastrophic blow to archaeocyathids, stromatoporids and early corals, the primary reef builders at the time. These crucial habitat creators did not recover for another hundred million years. All complex life lived in the seas at this time and marine extinction rates climbed to 80% killing off jawless fish and placoderms (armored fish) in the process. Interestingly enough although plant life had found its way to the land as well as amphibians and insects they seem relatively unaffected by this extinction.

Even more interesting is the fact this plant explosion may have been the downfall of its marine relatives. Plants reduce carbon dioxide in the air and with plants suddenly growing on the land in vast quantities the Co2 levels would have plunged pretty dramatically. This could have caused global cooling as well as causing anoxia, a lack of oxygen, in the water by being the first living things to change landscapes. These new plants dug their roots deep into the rocks at the time, breaking it up into sediment that then washed into the water in effect smothering everything under it.

The Devonian Mass extinction may have actually been a collaboration of up to seven separate lesser extinctions spanning 25 million years. If anything it was a slow process.

Trilobite of the species Lichas furcifer that went extinct during the Permian. Check out it's crazy head adornment!
Trilobite of the species Lichas furcifer that went extinct during the Permian. Check out it's crazy head adornment!

The Permian Extinction

251 million years ago the earth and seas saw the most complete extinction rate ever losing up to 96% of marine life and 70% of land based animals in a three stage extinction that went from the sea to the land and back to the sea. Sometimes called The Great Dying or “the mother of all extinctions” this is the only extinction to take with it a large number of insects.

A lot was going on in the world when this extinction took place so there’s still some debate about what caused it. Some say that it was the formation of Pangea, the singular and super continent that reduced sea shelves and killed off marine animals. Others think that it was another problem with Co2 and oxygen levels. Besides the formation of Pangea there were also the biggest volcanic eruptions ever to happen on the planet earth. These super eruptions were not caused by volcanoes but enormous vast cracks in the earth as the fault lines moved. Whole sheets of lava could spew from these openings for hundreds of years. This may have made the temperature of the earth rise by as much as ten degrees. This would have turned most temperate habitats into deserts and killed off all but the most adaptable of creatures.

Triassic ammonite uncovered in Germany
Triassic ammonite uncovered in Germany

Triassic Extinction

199 million years ago something caused 50% of all marine animals to suddenly die off and up to 80% of all land animals. This era was defined by creatures most people have never heard of that were somewhere between a reptile and a mammal, called conodonts. They all died out as well as most of the giant amphibians and the oceans didn’t fare much better with up to twenty percent of all marine families disappearing.

Parasaurolophus, one of the many dinosaurs to go extinct.
Parasaurolophus, one of the many dinosaurs to go extinct.

End Cretaceous

The late Cretaceous extinction is the one most people know about. It happened 65 million years ago and claimed all the dinosaurs as its most popular victims. They weren’t the only ones to die out as in the sea ammonites, a highly populous species over many millions of years, went with them. This was one of the least deadly extinctions though as only 60-75% of all animals died during this time. On land the dinosaurs died, in the air the pterosaurs flew into the horizon for the last time, and in the sea plesiosaurs memorialized themselves in the fossil record. Although reptiles had among the highest casualties they didn’t come close to the algae, of which up to 90% of all species ceased to be. This is important because little algae are the base to so many ecosystems and food chains that their loss would have been devastating to things far higher up on the food chain.

A meteor impact has been blamed for this mass extinction for many years but how? Basically a space rock six miles across entered the atmosphere and came colliding towards the earth striking what is known today as the Yucatan Peninsula. This killed everything in the area immediately in a rainstorm of fire and ash. It also sent up a great ripple of tsunamis which first crashed ashore and then flooded the coastal regions. The shock would have set off massive volcanic eruptions raising CO2 levels and creating acid rain and the impact would have kicked up a lot of dust that would have made a massive cloud that could have caused a nuclear winter. It’s a nice theory, a bit overdramatic, and it doesn’t sit well with people who believe in Ockham ’s razor (the simplest answer is usually the correct one.) A clue may be in the fact that land-based plant life seems to also have been killed off unlike most other extinctions. Another clue may be in the fact that this extinction appears to have been relatively rapid compared to the others.

Perhaps an even greater mystery is the survival of the animals that lived past the extinction. Large dinosaurs were likely targets in extinction because their massive size means they need massive amounts of food and are fairly inflexible to change. However most dinosaurs were not huge, they were the size of chickens, dogs, and cows. Why did they go extinct while turtles and crocodiles lived on? And why did the tiny mouse-like mammals come to take over the planet with the birds of the time? We’re still trying to figure this one out.

Dodo bird, went extinct at at the end of the 17th century due to over hunting and the introduction of cats, dogs, and pigs to its habitat.
Dodo bird, went extinct at at the end of the 17th century due to over hunting and the introduction of cats, dogs, and pigs to its habitat.

Today

Most people do not realize that scientists are starting to publicly state we are now in the grips of another mass extinction. We are losing the same amount of animals now as were calculated during the extinction of the dinosaurs. The answer to this is pretty obvious – humans. Over hunting, overfishing, the introduction of invasive non-native species, habitat loss, the rise of Co2 emissions, widespread pollution, and global warming make up for many of the contributing factors. Alarmingly we’re seeing the same pattern here as we do in the fossil record. The first species to die out are often the carnivores. Look now at the animals in most critical need of our protection: wild canids, bears, and the large cat species. Once predators disappear old and diseased animals live longer to infect the rest of the herd and overpopulation often leads to rampant starvation as the food sources are depleted. Biologist speculate that as much as one fifth of all life on earth and in the oceans today could be extinct in the next 30 years, and 50% of all species could be dead in the next 100. There is hope though; we as a species can change this. Simple people doing simple things like recycling, reducing their carbon footprint, and by only supporting industries that are self-sustaining can have a huge impact. We can also donate to charities that are working to save certain species and we can cut down on the seafood we buy and eat. We can also support the farming of various meats such as fish instead of capturing them from the wild. Stay informed, make good decisions, and respect the world you live in.

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Comments 9 comments

Seeker7 profile image

Seeker7 4 years ago from Fife, Scotland

Excellent hub with fascinating information and insight into the extinctions.

Life always seemed to find a way to recover - here's hoping that the human species will help the recovery today and not be the cause of another global disaster.

Voted up!


American Romance profile image

American Romance 4 years ago from America

You KNOW all these things happened billions and millions of years ago, just as you say? Yet you probably believe we have global warming and in just 20 tiny years the glaciers will melt and Florida will be flooded! I'm not coming down on your hub nor the excellent writing! I'm just sure your research came from some moron scientist that believes way too much! I don't believe the earth is that old. Here is something to think about! Remember Mount St Helens? After the explosion and giganctic mud slides the entire mountain ranges around shifted and mini plates shifted. Christian Scientist dug away and found dated layers that scientist have used for years to determine age! These layers indicated 2 million years old!..........Only one problem? These layers were built overnight because of a gigantic volcano!........kinda takes the fun out of it huh?


tsadjatko profile image

tsadjatko 4 years ago from maybe (the guy or girl) next door

Using your own words "Perhaps an even greater mystery..." is how anyone can talk of these "extinctions" as if the theories of what happened are fact! They are not fact but only theories with some supporting evidence (mostly based on assumptions that can not be proven)and some contradicting evidence based on fact.

In light of the the University of East Anglia's Climate Research Unit scandal you have to be pretty naïve in today's world to trust a scientific community that constantly portrays theory as fact and actually lies to create models or evidence that support a political agenda - that is not science but sadly characterizes many of the scientific "elite" today (and not surprisingly in the past, when you look at the "theories" based on faked "scientific" evidence and conclusions scientists have made in the past that are clearly revealed by today's advances in science and technology to have been motivated by their agendas!).


Melis Ann profile image

Melis Ann 4 years ago from Mom On A Health Hunt

Nice summary on each extinction period and the message that we better clean up our act as a society to avoid another extinction. Regardless of how long the next mass extinction may take to unfold, it's still in our best interest to curtail some of our habits. Voted up and SHARED!


Theophanes profile image

Theophanes 3 years ago from New England Author

You know, I have left these two first negative comments unapproved for six months not because I feared you'd put a bad light on my article but because I haven't much to say back to them. I have been here at HubPages for several years now and I think as a whole it's a very positive community with people encouraging each other, giving helpful hints and little reminders to fix typos and spelling errors.... but these two comments are way out in left field. They're mean, they provide nothing to work with, and they make no sense whatsoever. Does it really make you feel better to attack someone whose article you know by title alone you will not agree with? Of course I do not know everything. I am not God. However I, as a human, as a being, as a logical entity, believe what science tells me and that is exactly what this article is about. My title gave no illusion otherwise, so why you clicked on it is beyond me. So please - before you go on to break the spirits of someone with less of a thick skin than I, think about it twice. You better believe I won't be reading any of your hubs and I definitely won't be stopping by to slander their author either. Thank you for your concern.


Fossillady profile image

Fossillady 3 years ago from Saugatuck Michigan

Yeah, One of my favorite subjects! Amazing how it took 100 million years for life to fully recover after the Permian extinction! Great write up. Never mind those two nay-sayers. It's obvious they do not understand the scientific process! I'm glad you spoke your mind! Your hub friend, Kathi


Theophanes profile image

Theophanes 3 years ago from New England Author

Thank you for your kind words fossillady. The world has many stories to tell, and I think some of the ones coming from fossils are the most fascinating as well. :)


Nathan Orf profile image

Nathan Orf 2 years ago from Virginia

Nice comeback to American Romance and tsadjatko. And a good hub all around. You really know your stuff, but mass extinctions are frightening to contemplate, knowing what is going on now. I can't help but think that our own time on this world is limited at best.

Voted up and interesting.


Theophanes profile image

Theophanes 2 years ago from New England Author

Ah, I cannot help to think similarly. If we don't smarten up soon we're going to do a terrific job of committing a whole-species suicide. I used to pin my hopes on space travel - maybe the brightest will escape - but with NASA first drastically decreased a couple years ago and now practically shut down with the government throwing a temper tantrum I just don't know. Who needs science anyway? What has it ever given us? *rolls eyes*

Thank you for the kind comments. I am happy at least some people find this article useful, as scary as it might be.

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