Caldera
About 75,000 years ago, the Toba catastrophe released about 2,800 km3 of ejecta. This was the largest known explosive eruption within the last 25 million years.  In the late 1990s, anthropologist Stanley Ambrose suggested that a volcanic winter induced by this eruption reduced the human population to about 2,000  20,000, resulting in a population bottleneck. Others suggested that the human race was reduced to about five to ten thousand people.