I was recently discussing astrophysicist Neil deGrasse Tyson with my son Will and noted that he is going into production for another Cosmos television series, which will be aired in 2019. Can't wait! I mentioned that my favorite episode of Tyson's 2014 series...which was based on the late Carl Sagan's 1980 Cosmos series and updated it...was the episode about the Permian Extinction, which wiped out 96% of all species of Earth. It got me thinking of looking on the Internet for a good list of the major mass extinction events that have occurred over time. On worldatlas.com, I found a good list, which you can access through this link: [link]. To this list I added another event: "Snowball Earth", which occurred around 650 million years ago. And now here's that list of mass extinction events, going from earliest to latest...
SNOWBALL EARTH (650 million years ago)
All life at this time was unicellular and ocean dwelling...the extinction rate thought to be high, but how high is unknown. The causes of Snowball Earth...scientifically termed "global glaciation"...are in dispute as well as its duration and the extent of the ice covering. But it was most likely ended through volcanic activity that sent carbon dioxide upward to heat and melt the ice...
ORDIVICIAN-SILURIAN (439 million years ago)
According to the article, 86% of life was obliterated. The suspected cause of the extinctions was glaciation and falling sea levels.
LATE DEVONIAN (364 million years ago)
75% of life lost. Occurred possibly over thousands of years as land-based plants released nutrients into ocean, depleting oxygen through resulting algae.
PERMIAN-TRIASSIC (251 million years ago)
96% of species made extinct when a network of large Siberian supervolcanoes erupted, starting a chain reaction of carbon dioxide...and then methane...release into the atmosphere, overheating it and poisoning the oceans. Not a good time to be on Earth...
TRIASSIC-JURASSIC (199-214 million years ago)
Various reason, including a possible asteroid collision, are given for this change that occurred over a relatively long stretch of time. It paved the way for the advent of the dinosaurs...
CRETACEOUS-PALEOGENE (65 million years ago)
You've probably seen the scene portrayed on TV where the Tyrannosaurus Rex suddenly looks up and sees a fiery asteroid plummeting and striking the Earth. This is the famous event that rendered the large dinosaurs extinct and opened up the Earth's ecosystems for the evolution of mammals. Thank you, asteroid. But about 76% of life was destroyed during this extinction...
HOLOCENE (now)
Through human activity and its resulting climate change, the extinction rate has sharply increased. It's bound to get worse...
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