The fascinating true story of the explosion of the Mount Toba supervolcano--the Earth's largest eruption in the past 28 million years--and its lasting impact on Earth and human evolution. Some 73,000 years ago, the huge dome of Mount Toba, in today's Sumatra, Indonesia, began to rumble. A deep vibration shook the entire island. Jets of steam and ash emanated from the summit, followed by an explosion louder than any sound heard by Homo sapiens since our species evolved on Earth.