The last Mt. Fuji eruption was in 1707. Although silent now, it was the scene of several explosions in the past.
The Hoei Eruption 1707
As the last explosion it was also one of the most powerful. The explosions began in mid December but it continued sporadically for a couple of weeks. In total the blasts lasted until January. Estimates showed that over 700 million cubic ft of ash were spread a hundred kilometers away.
This is confirmed by the presence of the cider ash in Edo. Other places that were affected included Sagami and Izu. The power of the blast resulted in the formation of the volcanic vents. This Mt. Fuji eruption was also characterized by earthquakes.
The earliest known explosion in the area took place 700,000 years ago. The current volcano is only a few thousand years old. However there were volcanoes in the area at the time. It was known as Komitake. It has been established that it was active during this period.
Komitake / Old Fuji
The volcano in the area was already known as Old Fuji. This explosion was more powerful than the previous one. It spewed lava, ash and rocks. The resulting blast led to the creation of an island mountain. It measured over 3,000 meters.
New Fuji: 5,000 Years Ago
This Mt. Fuji eruption was characterized by the presence of magma. It also had elements of scoria and ash. The blasts resulted in structure collapses. This explosion is considered as the most varied. It contained various elements that were not part of other eruptions.
These consisted of four outbursts. These occurred 3,000 years ago. The explosions were characterized by black ash and were felt as far as Hamamatsu.
The Gotemba Mud / Lava Flow
This one occurred 2,300 years ago. The blast was so powerful that the eastern section of the volcano was destroyed. The resulting mud flow went all the way to Gotemba. The flow also made its way to Suruga Bay. This Mt. Fuji eruption covered a large portion of the land in mud and lava.
These explosions took place circa 864. The exact date is unknown. What is known is that the explosion destroyed the north face of the volcano. Scientific evidence indicates that the explosion was marked by strong lava flow. It isn’t clear if it was accompanied by pyroclastic material or black ash.
There have been a total of 16 eruptions on record from 781 onwards. These explosions are divided into eras. The Heian Era is the earliest. It is the period between 800 and 1083. In that time period there were a dozen eruptions. The inactive and quiet time lasted from 1083 to 1511. The last was the aforementioned Hoei blasts. It should be noted that the dates for these explosions (especially the early ones) are approximates.
There is no indication that the Mt. Fuji eruption will resume anytime soon. Silent for centuries now, it is still nevertheless one of the most awe inspiring volcanoes in the world.