Japan contains more than 100 active volcanoes. Of these, none are famous as Mount Fuji. This volcano
has produced more than 50 volcanic eruptions in the last 10,000 years, the most recent of which
occurred between 1707 and 1708. As a result of its frequent eruptions, it is only a matter of
time before this beautiful mountain erupts again. This video will discuss this active
volcano, and mention what its future hazards are. Mount Fuji can be found in eastern central Japan.
Specifically, it is 95 kilometers west southwest of the nation's capital, Tokyo.
When snow is not on the mountain, you can observe Fuji's beautiful crimson red coloration. This
coloration exists due to thick layers of scoria near its summit. Scoria is a variety of basalt
which does not typically erupt on a stratovolcano. Most stratovolcanoes have a gray to black color
due to the lava they erupt being andesite. However, Fuji primarily erupts basalt and scoria.
Mount Fuji is a stratovolcano that is a result of several volcanic cones building on top of portions
of one another. The first of its cones, known as Komitake, began forming 700,000 years ago.
Over the next 500,000 years, this volcano erupted basaltic lava.
The remnant of this period of volcanic activity can be found on the north slope of Mount Fuji.
Around the same time, another volcano known as Ashitaka erupted 17 kilometers to the south.
Some of the ash and lava from this volcano deposited on top of erupted rock from Komitake.
After a period of dormancy, a new cone known as "Old Fuji" began to form 80,000 years
ago. This vent formed 3 kilometers southeast of the main summit of the modern Mount Fuji.
Over the next 64,000 years, numerous eruptions of basaltic lava and ash caused
this mountain to climb to 2700 meters tall. The subsequent volcanic cone which we refer
as modern mount Fuji began erupting only 14,000 years ago. Over the next several thousand years,
it erupted a very large volume of basalt lava which contained olivine.
As the volcano continued to build, new eruptive vents opened around the mountain.
One of these in 1030 BC created a new cinder cone known as Mount Omuro 11 kilometers to
the northwest. Although many large eruption continued to occur at Mount Fuji's main summit,
more frequent eruptions occurred on its flanks through the construction of cinder cones.
Over the next several thousand years, around 20 cinder cones were built.
The largest known eruption at Mount Fuji in historic times occurred for 71 days between 1707
and 1708. This eruption created three large craters on Mount Fuji's southern summit. The
largest of these is more than a kilometer wide. During this eruption, pyroclastic flows raced down
the southern slope of the mountain, and several centimeters of ash fell as far away as Tokyo.
Since then, there have been no additional confirmed eruptions.
Today, the mountain is quiet, although on occasion large earthquakes occur in its
vacinity. Statistically speaking, the odds of an eruption in any given year are about 1 in 173.
If an eruption was to occur, it would present a variety of hazards. And no,
despite what tabloids ridiculously claim, an eruption from Fuji will NOT destroy Tokyo.
To understand what could be impacted, we need to discuss both of its eruption types.
If an eruption from its main summit was to occur, low lying areas up to 40 kilometers
away could be effected by lahars. If Mount Fuji has a lot of snow on its summit at
the time of an eruption, it would melt and created a phenomena similar to a very large
flash flood. As a result, evacuations would be needed from low lying areas. Additionally,
if a large eruption was to occur similar to what happened in 1707,
pyroclastic flows could reach a number of towns within 16 kilometers of its summit.
A much more likely style of eruption would create a cinder cone somewhere within 11 kilometers
of the main summit. These main threat from this style of eruption would be slow moving lava flows,
which could slowly travel up to a dozen kilometers. Both eruption styles would
result in several millimeters to meters of ash being deposited in an area around the volcano.
Although Mount Fuji is a very high threat volcano, it is completely safe
to visit and I recommend the experience. I hope that you enjoyed this video. If
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