The pyroclastic flows, as indicated in March

The prefectural governments of Shizuoka, Yamanashi and Kanagawa adopted
the first comprehensive evacuation plan on Thursday to prepare for a
possible eruption of Mount Fuji, Japan’s highest peak.

The evacuation plan calls for 750,000 people leaving their homes in 14
municipalities in Shizuoka and Yamanashi due to lava and pyroclastic
flows, as indicated in March 2013.

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In addition, 470,000 people, mainly in Kanagawa, would need to evacuate
because of volcanic ash in the air, according to the latest plan.Just a Matter of Years
Since the Great Tohoku Earthquake of March 2011, scientists have been watching Mt Fuji for signs of activity.

The new readings, taken by the National Research Institute for Earth
Science and Disaster Prevention, reveal that the pressure is at 1.6
megapascals, nearly 16 times the 0.1 megapascals it takes to trigger an
eruption.

Therefore the pressure in Mount Fuji’s magma chamber is now higher than
it was in 1707, the last time the nearly 4,000-metre-high Japanese
volcano erupted, causing volcanologists to speculate that a disaster is
imminent.

According to retired professor Masaaki Kimura ( Professor Emeritus from
the Faculty of Science of the University of the Ryukyus, Okinawa, Japan )
this and other recent phenomena indicate an eruption of Mt Fuji should
have taken place in 2011 with a four-year margin of error ending in
2015.

In 2000 and 2001 a series of low-frequency earthquakes were recorded
beneath the volcano, leading to widespread predictions of an imminent
blow. Since the March 2011 tsunami and the 6.4 magnitude earthquake that
followed four days later, Japan has been on tenterhooks, and in May
2012 Masaaki Kimura warned that a massive eruption within three years
would be likely because of several major factors: steam and gases are
being emitted from the crater, water eruptions are occurring nearby,
massive holes emitting hot natural gases are appearing in the vicinity
and finally, the warning sign that pushed the professor to make the
announcement, a 34km-long fault was found underneath the volcano.

The fault, experts suggested, could indicate a total collapse of the
mountainside if there is another significant shift, and it would
probably cause a collapse in the event of an eruption, leading to huge
mud and landslides.

Professor Toshitsugu Fujii, the head of Japan’s volcanic eruption
prediction panel, says an eruption could cause chaos and carnage all the
way to Tokyo.

“Mount Fuji has been resting for 300 years now, and this is abnormal. It
usually erupts in some form every 30 years. So the next eruption could
be a big-scale explosive eruption
If there is a large eruption, the government fears it could cause more
than $30 billion in damage to public health and agriculture. Volcanic
rocks will fall near the mountain.
Ash accumulations in some areas could be as high as 60 centimetres. Even
Tokyo, 100 kilometres to the north-east, could be coated in volcanic
ash. Tokyo will be covered in a few centimetres of ash. Yokohama will be
under 10 centimetres. Trains will stop, planes won’t fly and crops will
fail. Millions will be affected”, said Professor Toshitsugu Fujii.Geology

Mount Fuji is located at the triple junction where the Amurian Plate,
the Okhotsk Plate, and the Philippine Sea Plate meet. Those plates form
the western part of Japan, the eastern part of Japan, and the Izu
Peninsula respectively.

Scientists have identified four distinct phases of volcanic activity in
the formation of Mount Fuji. The first phase, called Sen-komitake, is
composed of an andesite core recently discovered deep within the
mountain. Sen-komitake was followed by the “Komitake Fuji,” a basalt
layer believed to be formed several hundred thousand years ago.
Approximately 100,000 years ago, “Old Fuji” was formed over the top of
Komitake Fuji. The modern, “New Fuji” is believed to have formed over
the top of Old Fuji around 10,000 years ago.

The volcano is currently classified as active with a low risk of
eruption. The last recorded eruption was the H?ei eruption which started
on December 16, 1707 (H?ei 4, 23rd day of the 11th month) and ended
about January 1, 1708 (H?ei 4, 9th day of the 12th month) during the Edo
period. The eruption formed a new crater and a second peak (named
H?ei-zan after the Hoei era) halfway down its side. Fuji spewed cinders
and ash which fell like rain in Izu, Kai, Sagami, and Musashi. Since
then, there have been no signs of an eruption. In the evening of March
15, 2011, there was a magnitude 6.2 earthquake at shallow depth a few
kilometres from Mount Fuji on its southern side. But according to the
Japanese Meteorological Service there was no sign of any eruption.

In September 2012, mathematical models created by the National Research
Institute for Earth Science and Disaster Prevention suggest that the
pressure in Mount Fuji’s magma chamber could be at 1.6 megapascals
higher than it was in 1707.

However, since there is no known way to directly measure the pressure of
a volcano’s magma chamber, such research is only speculative.

Historic Eruptions Of Mount Fuji

Mou
nt Fuji is the highest volcano in Japan. The mountain as it appears now
is the “New Fuji volcano”, which began to erupt about 10,000 years ago.
Under the “New Fuji volcano” lies the “Old Fuji volcano”, which was
active between 100,000 years ago and 10,000 years ago and the “Komitake
volcano”, which became active 700,000 years ago.

Komitake
There has been much volcanic activity in the vicinity of Mount Fuji for
several million years. In the location occupied by the current Mount
Fuji, a volcano known as Mount Komitake (?????), literally meaning
“small mountain volcano”, became active 700,000 years ago. Around this
time, another volcano, Mount Ashitaka (???), in the area to the
south-east of Mount Fuji, was also highly active. The peak of the
ancient volcano, Komitake, can be seen from the north face of Mount Fuji
at the fifth station, about 2,300 meters (7,500 ft) above sea-level.

Old Fuji
Around 100,000 years after becoming inactive, Komitake entered another
period of activity. The volcano in this period is known as Old Fuji (???
kofuji). Older Fuji was known as to have explosive eruptions, throwing
out large quantities of scoria, volcanic ash and lava, forming a large
mountain which reached a height of 3,100 meters (10,200 ft).

New Fuji
Following the Old Fuji period, there were about 4,000 years of
inactivity, ending at around 5,000 years ago, when Mount Fuji became
active again; this period is known as New Fuji (??? shinfuji), and
continues to the present day. Eruptions of New Fuji exhibit phenomena
such as lava flows, magma, scoria, volcanic ash, collapses and side
eruptions, leading it to be called “a department store of eruptions”.
Ash from New Fuji is often black, and eruptions are new in terms of
geological layers. Valuable data on the activity of Mount Fuji is
recorded in Japanese historical documents dating from the 8th century
onwards. It exhibits a range of representative eruptions.

Explosive eruptions before the activity 3005 years ago
There were four explosive eruptions in the J?mon era, which are known by
the names Sengoku scoria (Sg), ?sawa scoria (Os), ?muro scoria (Om) and
Sunazawa scoria (Zn). As the wind normally blows from the west in the
area of Mount Fuji, most ejectants fall to the east, but in the case of
the ?sawa scoria, they were carried on the east wind, as far as the
vicinity of Hamamatsu.

The Gotemba mud flow
About 2,300 years ago the east face of the volcano collapsed and liquid
mud flowed down to the Gotemba area as far as the Ashigara plain in the
east and the Suruga bay across Mishima city in the south. This incident
is now called the Gotemba mud flow (????? Gotemba deiry?). Liquid mud
piled up over an area as wide as the city area of Mishima.

J?gan eruption
In 864 (the 6th year of the J?gan era) there was an eruption on the
north-east side of Mount Fuji, which produced a great amount of lava.

864 (J?gan 6, 5th month): Mount Fuji erupted for 10 days, and it ejected
from its summit an immense quantity of cinders and ash which fell back
to earth as far away as the ocean at Edo bay. Many people perished and a
great numbers of homes were destroyed. The volcanic eruption began on
the side of Fuji-san closest to Mount Asama, throwing cinders and ash as
far away as Kai province.

Some of the lava filled up a large lake Senoumi (???) which existed at
the time, dividing it into two lakes, Saiko (??) and Sh?jiko (???). This
is known as the Aokigahara lava (??????), and at present is covered by
the dense Aokigahara forest.

H?ei eruption
The latest eruption, in 1707 (the 4th year of the H?ei era), was known
as the great H?ei eruption. It followed several weeks after the Great
H?ei earthquake:

– November 11, 1707 (H?ei 4, 14th day of the 10th month): The city of
Osaka suffers tremendously because of a very violent earthquake.
– December 16, 1707 (H?ei 4, 23nd day of the 11th month): An eruption of
Mt. Fuji; the cinders and ash fell like rain in Izu, Kai, Sagami, and
Musashi. This eruption was remarkable in that it spread a vast amount of
volcanic ash and scoria over a region as far away as Edo.

Records of eruption
Sixteen eruptions of New Fuji have been recorded since 781. Many of the
eruptions occurred in the Heian era, with twelve eruptions between 800
and 1083. Sometimes inactive periods between eruptions lasted for
hundreds of years, as in the period between 1083 and 1511, when no
eruptions were recorded for over 400 years. At present, there have been
no eruptions since the Hoei eruption in 1707-1708, around 300 years ago.

Who’s Professor Masaaki Kimura?

Masaaki Kimura graduated in science at the Faculty of Fisheries of the
University of Tokyo (1963) and obtained a Doctorate in marine geology
(1968). He has worked for the University of Tokyo’s Ocean Research
Institute, the Geological Survey of Japan, the Agency of Industrial
Science and Technology of the Ministry of International Trade and
Industry of Japan, and Columbia University’s Lamont-Doherty Earth
Observatory. He taught at the University of the Ryukus from 1977 to
2002.

He has since retired from that University and is now general director of
Marine Science and Culture Heritage Research Association.