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Answer: (c) 100

The summit crater

Craters on Mount Fuji

Most volcanoes experience eruptions from their ancillary hills, in addition to eruptions out of their summits. Craters located on ancillary hills are referred to as lateral craters. For example, the 1707 eruption of Mount Fuji occurred on a peak to the southeast of the summit. The Hoei crater created during that eruption is visible even today.

The formation of lateral craters form as a result of various kinds of geological factors. For example, craters formed in Japan are created from stress exerted on the rock from the vertical movement of plates. In addition to the strength of this pressure, the direction also effects the formation of craters. Lateral craters tend to form in the direction of the area which experiences the most stress. Mount Fuji has many such lateral craters and most of these exist along the north-northwest and south-south east axis, which were caused when the Izu Peninsula collided up against Honshu Island. It is generally thought that lateral craters which have erupted once will never erupt again.

The Position and Shape of Mount Fuji

A typical composite volcano, Mount Fuji has a wide base spreading gently out in four directions with slopes that become dramatically steeper toward the peak. It is for this perfectly symmetrical conical shape which Fuji is famous. The major geological activity influencing Mount Fuji’s volcanic activity is the Pacific Ocean plate, which is colliding with and being subducted under the Philippine Plate. This huge tectonic collision has resulted in the creation of many volcanoes along the same volcanic belt as Mount Fuji. In addition to the colliding of oceanic plates, Mount Fuji is also influenced by the northward extension of the underwater Japan Trench along the place where the Izu Peninsula is colliding with Honshu.