The Five Mass Extinctions
A multitude of species have vanished in the five cataclysmic mass extinctions, and as of today, about 99.9 percent of all species that have existed on Earth are extinct. These five extinctions were the Ordovician-Silurian extinction, the Late Devonian extinction, the Permian-Triassic extinction, the End Triassic extinction, and the Cretaceous-Tertiary extinction. They wreaked havoc on more species than you could imagine, and if you think today that there are a lot of species, imagine if the five mass extinctions hadn't happened. The Ordovician-Silurian extinction occured about 459 million years ago. There'd been a drop in sea levels as glaciers formed, followed by rising sea levels as the glaciers melted. Over 25 percent of marine families and 60 percent of marine genera were lost. The Late Devonian extinction took place about 364 million years ago. The cause, to this day, is unknown. However, there is evidence suggesting that warm-water marine species had been the most severely affected during this particular extinction, and it's led many paleontologists into believing the cause to be a case of global cooling. Furthermore, the Permian-Triassic extinction happened about 251 million years ago, and was said to be the Earths worst mass extinction. Among those killed in this catastrophe include 95 percent of all species, 53 percent of marine families, 84 percent of marine genera, and an estimated 70 percent of land species such as plants, insects, and vertebrate animals. The End Triassic extinction took place roughly 199 to 214 million years ago. Its cause was most likely the massive floods of lava that had erupted from the central Atlantic magmatic province, which induced the breaking apart of Pangaea and the opening of the Atlantic Ocean. Other scientists suspect that it was the impact of a comet or asteroid that had triggered the volcanism. And, lastly, the Cretaceous-Tertiary extinction took place somewhere around 65 million years ago, and is thought to