Research: Fuji developing a more explosive style? 6 May 2010Posted by admin in current research, Fuji, Japan, volcanoes, volcanology.
Tags: Fuji, Japan, volcanological research
‘Rumbles hint that Mount Fuji is getting angry’, says the rather sensationalized headline that New Scientist has stuck over their report of a new study of Mount Fuji. There’s no suggestion in the original research paper that Fuji is ‘getting angry’, or even slightly annoyed, just a new theorization of the processes that may be causing Fuji’s magmas to become more andesitic to dacitic, thus tending towards a more explosive eruptive style.
The paper, ‘Crypto-magma chambers beneath Mt. Fuji’ by Takayuki Kaneko et al (JVGR 2010, in press) notes that Fuji’s eruptive history has been characterized by basaltic activity with occasional explosive eruptions involving andesitic to dacitic lavas. Studies of Fuji’s lavas using air-fall scoria, however, indicate an increase in silica content over time: Kaneko proposes a two-level magma chamber system to account for this, with basaltic magma at the deep level and more silicic magma at the shallower level. The increasing level of silica, suggests Kaneko, ‘could result from the combination of repeated magma mixing between the two end-member magmas and fractional crystallization processes in each magma chamber’.
The upward trend of SiO2 … seems to continue to the present. In the last several thousand years, explosive eruptions involving a small volume of andesitic magma were repeated sporadically … Such andesitic or dacitic products have not been found from the older periods of Fuji–Ko-Fuji to the middle stage of Shin-Fuji volcanoes. This may suggest that, in the last several thousand years, the composition of the magma in the shallow chamber has become more SiO2-rich than ever.
The New Scientist article says that Kaneko interprets the low-frequency earthquakes detected beneath Fuji in 2000 and 2001 as possible evidence for magma injections into the lower chamber, ‘and adds he would not be surprised if Fuji erupts in the very near future’. That’s the ‘Fuji getting angry’ bit, and it’s stretching things somewhat on the basis of this research. The paper itself simply concludes with the suggestion that ‘Fuji may have entered a stage with the potential for explosive eruptions involving andesitic to dacitic magmas’.
- Takayuki Kaneko, Atsushi Yasuda, Toshitsugu Fujii and Mitsuhiro Yoshimoto, ‘Crypto-magma chambers beneath Mt. Fuji’, Journal of Volcanology & Geothermal Research, article in press 2010 [doi:10.1016/j.jvolgeores.2010.04.002]
Rumbles hint that Mount Fuji is getting angry – New Scientist, 5 May 2010