Over 99% of the animal species that have ever lived on the face of our planet have died off and are now extinct. Sometimes an event occurs, causing changes so drastic that most species are completely wiped out in a very short period of time. So, here are the 6 mass extinctions that changed the world.
Besides these, there were off course some other, smaller cases of widespread die-outs, but these six are the biggest mass extinctions in history. Thanks to the guys at AsapSCIENCE, we were able to tell you their story.
The Ordovician-Silurian mass extinctions – 440 Million Years Ago
At that time, most of life on Earth was in shallow seas, as they swam or crawled on the bottom sea floor. As newly created volcanic rock was eroded and worn down by water and wind, it reacted with the CO2 in the atmosphere, sucking it in. Yes, some rocks absorb CO2.
As a result, CO2 levels dropped and thus the temperatures cooled, leading to the shallow waters we previously talked about, to freeze. This caused ocean levels to drop significantly and shallow seas to drain and 86% of species died because of it.
Late Devonian mass extinctions – 374 Million Years Ago
Over millions of years, the oceans slowly regained their former levels and became populated with fish, while the land was colonized by early forms of plants. These plants were food for the first ever insects. These plants were the reason for this next extinction, the Late Devonian.
They again absorbed CO2 from the air, thus making the planet cool and changed the composition of the soil, which eventually ended up into the oceans. These nutrients washed up into the waters caused large numbers of algae to grow which in turn sucked up oxygen from the atmosphere. More than half of life was asphyxiated and choked to death.
However, a reptile-like fish with legs and lungs was able to survive. Over the next 100 million years, these creatures would evolve into amphibians, reptiles and in fact, nearly all modern day land animals.
Permian-Triassic mass extinctions – 250 Million Years Ago
This is the single most devastating of mass extinctions in history, where 70% of all animals on land and over 95% of life in the ocean were wiped out. This time came to be known as “The Great Dying”.
Due to a huge volcanic activity or possibly a meteorite impact, billions of tons of volcanic gases completely destroyed the planet’s ozone layer. The average ocean temperature reached temperatures of around 40 degrees Celsius (104 F.) which is hotter than your winter shower. Acid rain fell all across the planet, devastating life on land.
Triassic-Jurassic mass extinctions – 200 Million Years Ago
Not even 50 million years later and the world is again faced with a massive die off. By this time dinosaurs the size of cows or smaller were prowling the planet’s surface, alongside many other reptiles.
A huge volcanic rift opened in the middle of the planet, thus giving birth to the Atlantic ocean and splitting the Americas from Europe and Africa. The resulting volcanoes spewed out lava and CO2, rising the temperature and killing off roughly 80% of the species at that time.
Cretaceous-Tertiary mass extinctions – 65 Million Years Ago
Because of the void left behind by the previous extinction, dinosaurs were able to become the dominant animals on Earth. For the next 135 million years they did extremely well and grew to become the largest land animals that have ever lived.
Though not exactly sure, scientists believe that this extinction took place because of an asteroid the size of a small town hit the planet in what is now the Yucatan Peninsula in Mexico. The impact shot millions of tons of dust into the atmosphere, blocking out sunlight and spelling an end for all large animals.
The smaller dinosaurs that remained, are the chicken’s and other birds’ ancestors. The planet was now ready to be home to a rat like furry creature which would be the forefather of all mammals on Earth; including us.
Now, after all these extreme makeovers the planet went through, we humans are preparing it for another one. What in previous mass extinctions took millenia, today they happen in mere decades.
CO2 levels have risen to over 400 ppm (part per million), which hasn’t happened for millions of years. This greenhouse gas has climbed so high in just the last 50 years, which in geological terms is virtually no time at all.
Besides climate change, we humans have exterminated hundreds of animal species through hunting, fishing, habitat destruction and pollution, which is roughly 1000 times faster that normal. If all species which are at risk of going extinct today, will do so in the near future, we can proudly call ourselves the sixth of the major mass extinctions in Earth’s history.
What is worth remembering from the previous extinctions that took place so long ago, is that usually the big creatures died off, making room for the little guy to take over. Today however, species die equally, regardless of size. And if the little guy goes extinct, so will the one at the top of the food chain.