About 183 million years ago, volcanic activity in modern South Africa unleashed an estimated 20,500 gigatons of carbon dioxide (CO2) into the ocean–atmosphere system over a period of 300 to 500 thousand years. Known as the Toarcian Oceanic Anoxic Event (T-OAE), the lack of oxygen, or anoxia, in the water during this time caused a mass extinction of marine species.
