On Saturday, March 7, 2009 Mt. Fuji was particularly clear in the southwest distance. The day was cool-bordering-warm, sunny and with a strong breeze after a few days of cold and rain. At dinner that night I reported the clear sighting to my daughter.
“It’s the air,” she said. “It’s clean.”
“Yes, that’s true. But it is also because Mt. Fujiis closer to the city every year, I think.”
“Hmmmm. So.” (sounding unconvinced - why does everyone sound unconvinced when I tell them things?!)
It is a little known fact that Mt. Fuji - at 3,700 meters it is the highest peak in Japan, and rightly famous for its symmetrical lines - is gradually moving northeast, about 6 mm closer to Tokyowith each passing year. It is mountain is altering its size, shape and relative position by means of eruptions and lava accumulation not that urban expansion is stretching metropolitan Tokyo closer to
the mountain, or that the. No. It is that internal magma movement is physically nudging the entire mountain’s body to the right of the map. Strange but true mysteries of nature. Although Mt. Fujiis a dormant volcano it is not at all extinct, and it still rumbles and passes gas. It is safe to climb, and thousands of people ascend every summer. (Arriving at the peak in time to watch the sun rise is a particularly coveted experience.) Japan is well
known for its tectonic activity. With all the earth tremors and frequent minor earthquakes here/occasional major earthquakes Japan is a country on the move. But the movement ofMt. Fuji that I am referring to is not of that sort. It is volcanic, not plate tectonic. Certainly, volcanism is related to tectonic plate subduction - volcanoes dot subduction trenches around the world. But it is not moving northeast by 6 mm a year because of moving plates - at least not primarily. It is moving because of magma frequency. The centrifugal force of the Earth’s rotation, plus the Moon’s gravity, plus the naturally flexing magnetic field of the planet all combine to affect its internal fluid and sway the mountain and nudging its entire mass along the surface. It’s not unique to Mt. Fuji. A similar phenomenon can be measured throughout the world - and not just pertaining to mountains, either. But it is so slow, so slight, and the forces that account for it are so subtle that it goes without comment.