Fuji Sabo Works, an organization established by Japan's Ministry of Land, Infrastructure and Transport (MLIT) to fight erosion on Mt. Fuji, has released video of a powerful slush avalanche that occurred on Fuji's western side at 8:09 AM on March 25.
Slush avalanches happen when cold, dry snow suddenly becomes saturated with water. About 90 millimeters (3.5 inches) of rain had fallen before the avalanche occurred.
The avalanche took place in an area on Mt. Fuji called the Osawa Collapse (Osawa Kuzure), a 2.1-kilometer (1.3-mile) long gully that begins near the summit and runs down the western side. The gully is up to 500 meters (1,640 feet) wide and 150 meters (490 feet) deep in some places, and according to this Fuji Sabo Works project outline (PDF), a total of 75 million cubic meters (2.6 billion cubic feet) -- equivalent to 60 Tokyo Domes -- of soil has been displaced. An estimated 150,000 cubic meters (5.3 million cubic feet) of soil washes out through the Osawa Collapse each year.
[Via Slashdot Japan]