Paektu Mountain
Paektu Mountain on the Chinese–North Korean border had a VEI-7 eruption in 946. Paektu Mountain is mainly a threat to the surrounding area in North Korea and Manchuria. The west coast of Hokkaido is about away. However, a temple in Japan reported "white ash falling like snow" on 3 November 946 AD. So strong winds carried the volcanic ash eastward across the Sea of Japan. An average of of ashfall covered about of the Sea of Japan and northern Japan (Hokkaido and Aomori Prefecture). It took the ash clouds 1 day or so to reach Hokkaido. The total eruption duration was 4 and half to 14 days (111–333 hours).