Preliminary observation results on products of the 29 September eruption

 Tephra of the 29 September eruption were surveyed just after the eruption. Distribution of tephra was partly based on the survey results by Kusatu-Shirane Volcano Observatory, Tokyo Technology of Institute.

1. Ash distribution area is wider than that of the 23 September eruption.
2. Lapilli of 4 cm across is the maximum, 4 to 4.5 km away from the crater.
3. Lapilli consist mainly of black colored andesite, very rarely of white colored sedimentary rock and its partial melt, contrasting to those of the 23 September eruption.
4. The maximum weight of lapilli at places about 4 km away from the crater is larger than that of the 23 September eruption.
5. Heavy rain of this day will wash most of tephra away.

The magnitude of the 29 September eruption is a little larger than that of the 23 September, but smaller than that of the 1st September.

Reference data
The maximum weight of lapilli on places about 4 km away from the crater.
1 September   about 1,000 g/m2
23 September   about 100 g/m2
29 September   about 400 g/m2

     
Tephra distribution       Lapilli (5.2 km from the crater)