Reports of field survey on the tephra of the erupution in 2004/09/01
Figure 1 : The distribution of the weight of tephra(ash).
According to this result, it is estimated that total
weight of extravasate is about 45,000 ton (this value is
minimum though this result does not include cinders
and volcanic bomb at the moutaintop).
Figure 2 : The distribution of maximum grain size.
Cinders with a diameter of 5cm or more fell in the range of about 5km from the crater.
Figure 3 : The breadcrust bomb sampled at Kromamegawara where it is 3.5km northeast
of the crater of Asama volcano. This bomb has vitric film and vesicular interior.
The grass landed on by large lithic stones of this eruption were
charred at places about 3.5 km NE of the summit crater.
(ERI & AIST)
Figure 4 :
Chemical compositions of products of the 1 September eruption. Pumices
(bombs) and lithics (tow small dots) are close chemically to lavas of
1783 and 1973, and 1108 eruptions, respectively.
Figure 5 : Comparison of tephra between the 1983 and 2004 eruption. This map shows
that the 1983 eruption was larger in scale than the 2004 eruption.