In June 1912, the Novarupta volcano in Alaska spewed out about 520 million tons per hour of hot magma, ash and other debris over less than three days.
According to NASA, it was the largest eruption of the 20th century, "three times the size of the Pinatubo eruption and 30 times that of Mount St. Helens."
The explosion was so huge, ash from the volcano was found as far as Europe and the Greenland Ice Sheet.
Interestingly, scientists originally thought the eruption was caused by Katmai, a large, near-by volcano. The correct source was identified only decades later thanks to advances in modern technology.
The picture below shows Novarupta Dome and Katmai Caldera (just 6 miles away) on August 13, 2002.
The browns are hardened ash. The roughly 650-foot-deep crater lake at the center of Mount Katami was formed during the Novarupta eruption when magma being drained away caused the summit to collapse.
