The Millennium Eruption
In late 946 CE, the volcano beneath Changbai Mountain produced one of the most powerful eruptions of the last 5,000 years. Modern analysis of preserved trees and Greenland ice cores confirms the date of this cataclysmic event, known as the Millennium Eruption. It registered as a 6 or 7 on the Volcanic Explosivity Index (VEI), placing it in the same category as the 1815 eruption of Tambora.
The eruption column shot gas and ash more than 30 kilometers into the stratosphere. It ejected an estimated 23 cubic kilometers of dense rock equivalent material. Pyroclastic flows—fast-moving currents of hot gas and volcanic matter incinerated the landscape, filling valleys with deposits over 100 meters thick. The ashfall was immense, blanketing an area of 1.5 million square kilometers across the Sea of Japan and parts of northern Japan with a layer of fine particles. Historical chronicles from a temple in Nara, Japan, describe "white ash falling like snow" on a November evening in 946. When the eruption subsided, the mountain's summit collapsed, leaving behind a massive five-kilometer-wide caldera.