User:Connorhs25/Hōei eruption

Bibliography:

Sloshing of bubbly magma

Recent process of geophysical

Elastostatic effects around a magma

Monitoring quiescent volcanoes

Improvements:

- Improve lead of article

- Little more specific information such as describing how events began would be helpful.

- Add tectonic setting and vent diagrams/images (Added this image to the page)

- list damages associated with past eruptions and discuss how those affected the people living there at the time.

Lead
The Hōei eruption of Mount Fuji started on December 16, 1707 (during the Hōei era, 23rd day of the 11th month of the 4th year) and ended on February 24, 1708. It was the last confirmed eruption of Mount Fuji, with three unconfirmed eruptions reported from 1708 to 1854.  It is well known for the immense ash-fall it produced over eastern Japan, and subsequent landslides and starvation across the country. Hokusai's One Hundred Views of Mount Fuji includes an image of the small crater at a secondary eruption site on the southwestern slope. The area where the eruption occurred is called Mount Hōei because it occurred in the fourth year of the Hōei era. Today, the crater of the main eruption can be visited from the Fujinomiya or Gotemba Trails on Mount Fuji. 

Extent of eruption
Three years before the eruption, rumbling began in 1704 from February 4 to February 7. One to two months prior to the eruption, earthquakes could be felt around the base of the volcano with magnitudes reaching as high as 5. Due to the short time between the earthquake and eruption, these events have been linked together. The event was characterized as a plinian eruption, with pumice, scoria, and ash shot into the stratosphere and raining down far east of the volcano. It has been classified as an explosive eruption. Landslides soon followed the eruption due to heavy rainfall and flooding in the area. It is suggested that two types of magma, silicic and basaltic magma, mixed together as a result of the earthquake.

The eruption happened on Mount Fuji's east–northeast flank and formed three new volcanic vents, named No. 1, No. 2, and No. 3 Hōei vents. The catastrophe developed over several days; an initial earthquake with an explosion of cinders and ash were followed some days later with more forceful ejections of rocks and stones. The Hōei eruption is said to have caused the worst ash-fall disaster in Japanese history.

Although it brought no lava flow, the Hōei eruption released some 800 e6m3 of volcanic ash, which spread over vast areas around the volcano, even reaching Edo almost 100 km away. Cinders and ash fell like rain in Izu, Kai, Sagami, and Musashi provinces, and ash-fall was recorded in Tokyo and Yokohama to the east of the volcano. In Edo, the volcanic ash was several centimeters thick. The released ash from the eruption fell to the earth and covered many crops in the area, stunting growth. There is no estimate for the number of death caused by the eruption. The eruption is rated a 5 on the Volcanic Explosivity Index.

Tectonic setting and the threat of more eruptions
Japan is located in the most geologically active region of Earth, called The Ring of Fire. This region is known for its many volcanic eruptions and earthquakes. The location of Mt. Fuji puts it in the middle of three colliding tectonic plates, the Eurasian, North American, and Philippine Sea plate, resulting in the history of high geologic activity. The Hōei eruption was preceded by a magnitude 8.6 earthquake, just 49 days before the eruption. Many volcanologists believe that this earthquake was likely the cause of the eruption.

Based on the internal pressure inside the volcano that scientists measured in 2012, speculation of a possible eruption is high. There have been many earthquakes since the 1707 Hōei earthquake, with some minor activity in the 1980s, in the year 2000 and 2001, and the major Tohoku earthquake in 2011. After the activity observed in 2000, magma has been found to be collecting under the volcano. Damage is estimated to cost Japan over US$25 billion if another eruption were to occur. It is assumed that, much like the 1707 Hōei eruption, the volcano would almost certainly erupt at the same vent where the previous eruption occurred. A repeat of the 1707 Hōei eruption is also said to impact over 30 million people in the highly populated areas of eastern Tokyo, Kanagawa, Chiba and parts of Yamanashi, Saitama, and Shizuoka. The volcano would most heavily affect Tokyo, and would likely cause power outages, water shortages, and malfunctions in the highly technical city. Mt. Fuji has more than 20 seismic activity stations monitoring any movement in the ground. It is impossible to determine when the next eruption will occur, but it will most likely erupt soon due to the long dormancy time.