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Article: Hōei eruption

Edit: Adding a new section to the article. The paper talks about the effects of the eruption on the environment and the occupants, however, it doesn't mention the processes that were responsible for the eruption.

Cause of the Hōei Eruption [1]
It is hypothesized that the Hōei eruption was due to two earthquakes, namely Genroku and Hōei, with a magnitude of 8.2 and 8.7. The former took place in 1703 at the Sagami Trough while the latter occurred in 1707 at the Nankai Trough. The Hōei eruption happened forty-nine days after the Hōei earthquake. The Genroku quake was the largest to happen at the Sagami Trough, however, it wasn't enough to start the eruption, although it did contribute to the eruption. The main earthquake that triggered it was the Hōei quake which caused stress and compression of the magma chambers underneath Mount Fuji.

A dike system stretches from the surface of Mount Fuji to 20 km into the subsurface. At 8 km depth, there are magma chambers of a dacitic and andesitic nature while at the deepest portion of the dike, a basaltic melt is located. The dike acts as a conduit for the magma chambers to reach the surface. The Genroku event caused a change in the normal stress acting on the dike system which had the effect of clasping the dike as well as the melts. The magma chambers were compressed and the conduit (dike) itself was buckled, trapping the melts. The chambers were under great pressure, but it wasn't enough to force the magma through the surface. This changed with the arrival of the Hōei earthquake.

The Hōei event similarly affected the dike system as the Genruko quake in the sense that there were normal stress changes and buckling of the dike but the resemblance ends there. The normal stress was increased in the upper segment (8 km in depth) of the dike, clasping it. This forced the dacitic and andesitic magmas to remain in place. However, the Southeastern portion of the dyke which remained clamped by the Genruko quake was unbuckled due to the reduced normal stress in that area by the Hōei earthquake. This allowed for the basaltic melt, which was still being compressed, to rise and mix with the trapped dacitic and andesitic melts. This caused magma expansion due to the "vesiculation" of the now-mixed magma, allowing it to travel to the surface of Mount Fuji. It seems that the dilatation of the magma reservoir can cause gas bubbles to rise with the melt allowing more depressurization to occur. Thus, producing the Hōei eruption. However, one must keep in mind that there could be other important processes that played a part in bringing about the eruption. Indeed, the Hōei eruption occurred 49 days after the earthquake. This suggests that other procedures, such as the melt mixing through sloshing, could have taken place.

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