Here's why:

* Convergent Boundaries: These are areas where tectonic plates collide. The collision of the Pacific Plate (oceanic) and the Eurasian Plate (continental) is what created the Japanese archipelago, including Mount Fuji.

* Divergent Boundaries: These are areas where tectonic plates move apart, leading to the creation of new crust.

* Hot Spots: These are areas where plumes of hot magma rise from deep within the Earth's mantle, causing volcanic activity independent of plate boundaries.

In the case of Mount Fuji:

* The Pacific Plate is subducting (diving) beneath the Eurasian Plate.

* This subduction process melts the oceanic crust, creating magma that rises to the surface, forming volcanic arcs like the one that Mount Fuji is a part of.

So, Mount Fuji's volcanic activity is a direct result of the convergence of these two tectonic plates.