Mount Fuji Lava
Mount Fuji Lava
The tallest mountain in Japan, the formidable Mount Fuji actually consists of three volcanoes in one. Dormant for three centuries, its last eruption was triggered by an 8.7 magnitude earthquake and spewed more than 800 million cubic meters of ash over Japan.
This specimen is a piece of Mount Fuji lava from an erupton that occured in 864 AD. It is housed in a glass-topped riker case for easy examination.
The Magnificent Mountain
At 3,776 meters, Mount Fuji is the highest mountain in Japan. Yet, the modern Mount Fuji is actually three volcanoes in one: Komitake, Ko-Fuji, and Shin-Fuji. Over the course of the last several hundred thousand years, each volcano formed out of the remains of the last with Shin-Fuji becoming active roughly 10,000 years ago.
This specimen is part of a massive eruption which occurred in 864 AD. Lava poured from Mount Fuji and filled part of ancient Lake Senoumi, creating Lake Sai, Lake Shōji, and Lake Motosu. Pictured above, the fertile land left behind became the Aokigahara Jukai or “Sea of Trees”. This tranquil region also has the unfortunate distinction of being known as the Suicide Forest.
📸 A Mount Fuji Lava Specimen
The specimen was acquired from a local, family-owned stone quarry by a friend of Hans' who owns a cafe and bed and breakfast just outside the Aokigahara with spectacular views of the mountain. For five generations, this family has produced sculptures for Buddhist and Shinto Shrines around Mount Fuji.
As pictured, the specimen is housed in a glass-topped riker display box measuring 4x3x1 (inches). A small information card is included.
Please Note: Each specimen is unique, so size and shape will vary.
📸 misty rain / a day with Mount Fuji unseen: / so enchanting. -Matsuo Bashō (1644–1694)
More About Mount Fuji and the Hōei Eruption
📸 Cross-section of Mount Fuji and related volcanic piles (Source: “Evolution of Mount Fuji, Japan: Inference from drilling into the subaerial oldest volcano, pre-Komitakeiar_722 470..488”)
Forming Fuji
The modern Mount Fuji is actually three volcanoes in one: Komitake, Ko-Fuji, and Shin-Fuji. Over the course of the last several hundred thousand years, each volcano formed out of the remains of the last with the latest becoming active roughly 10,000 years ago.
Shin-Fuji went through several stages of development which included basaltic flows covering large areas to the north, west and southwestern foothills. The stratovolcano's symmetrical cone has served as an inspiration for artists for centuries and more recently for scientists studying the geometrical evolution of volcanoes.
The shape of a volcano is primarily determined by hydraulic resistance to the flow of magma in a porous medium. Mount Fuji in particular is an excellent example of this process.
📸 Fine Wind, Clear Morning, and 凱風快晴.
The Japanese artist, Katsushika Hokusai was also an admirer of Mount Fuji. His popular series of landscape prints, 富嶽三十六景 or Thirty-Six Views of Mount Fuji, show the mountain across the range of seasons and from many different views.
The image here comes from this collection. The print is known by several names, including "Fine Wind, Clear Morning," and "風快晴." The slope of the mountain's flank is nearly a perfect fit for the porous flow theory.
"From around the age of six, I had the habit of sketching from life. I became an artist, and from fifty on began producing works that won some reputation, but nothing I did before the age of seventy was worthy of attention. At seventy-three, I began to grasp the structures of birds and beasts, insects and fish, and of the way plants grow. If I go on trying, I will surely understand them still better by the time I am eighty-six, so that by ninety I will have penetrated to their essential nature. At one hundred, I may well have a positively divine understanding of them, while at one hundred and thirty, forty, or more I will have reached the stage where every dot and every stroke I paint will be alive. May Heaven, that grants long life, give me the chance to prove that this is no lie."
Katsushika Hokusai (1760–1849)
📸 Katsushika Hokusai's impression of the Hōei eruption.
Eruptions of Mount Fuji
Mount Fuji has been inactive for three centuries, but its current peace belies a fiery past. Its most recent eruption was the Hōei eruption, a year-long event triggered by an 8.7 earthquake that lasted from December 16, 1707 to February 24, 1708. The ashfall from this eruption was immense, with over 800 million cubic meters (28,200,000,000 cubic ft) released.
This followed other destructive eruptions. After the violent 864 Jōgan eruption, Emperor Seiwa’s government ordered Buddhist priests to be stationed around Mount Fuji, reading sutra holy texts to keep the volcano at bay.
📸 "Map of Mt. Fuji showing the extent of Hōei air-fall deposits, in terms of isopachs (after Miyaji, 1984 and Miyaji and Koyama, 2007), with locations of sampling section (FJ19 and FJ20). The isopach giving thickness in cm. The insert shows tectonic setting and the location of the main map (box)." (Source: "Petrological constraints on magma evolution of the Fuji volcano: A case study for the 1707 Hōei eruption.")
Front of the Specimen Card
Back of the Specimen Card
Further Reading
Fujita, Eisuke, et al. "Stress field change around the Mount Fuji volcano magma system caused by the Tohoku megathrust earthquake, Japan." Bulletin of volcanology 75.1 (2013): 1-14.
Lacey, A., J. R. Ockendon, and D. L. Turcotte. "On the geometrical form of volcanoes." Earth and Planetary Science Letters 54.1 (1981): 139-143.
Miyaji, Naomichi, et al. "High-resolution reconstruction of the Hoei eruption (AD 1707) of Fuji volcano, Japan." Journal of Volcanology and Geothermal Research 207.3-4 (2011): 113-129.
Sano, Takashi, Takaaki Fukuoka, and Mitsunori Ishimoto. "Petrological constraints on magma evolution of the Fuji volcano: A case study for the 1707 Hoei eruption." Studies on the Origin and Biodiversity in the Sagami Sea Fossa Magna Element and the Izu-Ogasawara (Bonin) Arc, Mem. Natl. Mus. Nat. Sci 47 (2011): 471-496.
Yamamoto, T., et al. "Basaltic pyroclastic flows of Fuji volcano, Japan: characteristics of the deposits and their origin." Bulletin of Volcanology 67.7 (2005): 622-633.
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