ῒΐ  /*  (,**/)
 0  .1/ῌ.23 

῕ ῔

,**+,





 



,

   ,**/  0  ,*  ,**/  ++  1 Fumarolic Activity since December ,**- and Volcanic Activity
during the Meiji and Taisho Eras (+22*ῌ+3,-) of
Ohachi Volcano, Kirishima Volcano Group, Southern Kyushu, Japan
Masaaki TSUTSUI῍, Katsutoshi TOMITA῍῍,῍῍῍ and Tetsuo KOBAYASHI῍῍
A new fumarolic activity at Ohachi Volcano of Kirishima Volcano Group started on December +-, ,**- after
about 2* years of inactivity. Two small fumarolic vents, T2 and T3, were formed on the slope within the Ohachi
crater. Ejected materials were mainly ﬁne-grained mud (altered ash), that were distributed within the southwestern sector of the crater. Small accessory lapilli, which were coated by mud, were scattered within ,* meters of
T2 vent. No essential material was found. Alunite, kaolinite, +* -halloysite were present as clay minerals.
The volume of ejected material was very small, probably less than +* m-. At the time of this writing, thefumarolic activity at Ohachi crater is still going on.
To understand the present activity, we investigated old documents of historic eruptions of this volcano, in
particular those that occurred during the Meiji and Taisho eras (+22*ῌ+3,-), to determine the mode of eruptions
during that time. The ﬁrst stage of the eruption started with a fumarolic activity, which became more active.
Then magmatic activities continued for about .* years. The early phase of magmatic activities was characterized
by vulcanian eruptions generating a large volume of ash, while the latter phase was characterized by sporadic but
strong vulcanian explosions accompanied by ejection of volcanic bombs and blocks.
At present, it would be di$cult to judge whether the fumarolic activity will become more active, and proceed
to magmatic stage. However, the results of our investigation of historical eruptions would still be useful topredict the nature of future eruption of this volcano.
Key words : Ohachi Volcano, Kirishima Volcano Group, fumarolic vent, documents of eruption, Meiji and Taisho eras+ῌ ῐ ῎ ῑ ῏+1  + @23_T`ab c&3d Ief,=I +/(,**-)  +,  +,  +/   !"#
*+,-

/ )1

$%&'(!"#) &.02345,62378
9: , ;<,=> ?@ 1 ABC+@23789

ghAij4DEkl78mno)LMNp GPS 4D
E'qrT78stuv,F@?Fmwx=>
F?yI+- 4z{MI|'4}Ux=F?y=U 1  I M

:4DEF +,  ++  +. G4.0HIJKFLMN.0~3mwE UM m*E,

EOPQ .* G@23RST  +1  ,  + UMn!I, 24,WN=n!UMn

VWN=STOPQ@X8YZ[\,]@^ ; <I4,6=> ?mn<@

--+ῌ20-2 W=-  ,ῌ,1,ῌ ¡¢£¤¥¦§¨©ª§« ¬­­®¯§ª°
DIA Consultant Co., Ltd., Sabo and Disaster Prevention Center, ,ῌ,1,ῌ- Yoshino-cho, Kita-ku, Saitama--+ῌ20-2, Japan.
23*ῌ**0/ $%&±² +ῌ,+ῌ-/$%&³´´µ'¶·¸¹´¹Earth and Environmental Sciences, Faculty of Science,

Kagoshima University, +ῌ,+ῌ-/ Korimoto, Kagoshima
23*ῌ**0/, Japan.
|º 23*ῌ*2*, $%&»¼ 1ῌ+.
Present : 1ῌ+. Shimizu-cho, Kagoshima 23*ῌ*2*,, Japan.
Corresponding author : Masaaki Tsutsui
e-mail : M. Tsutsui@diaconsult. co. jpf+)gh¼i¢Vjk

476

Fig. +. Location of fumarolic vents and distribution of ejected materials. a) Solid circles indicate new fumarolic
vents (T2 and T3). b) Solid and dashed lines indicate the limit of distribution of ejected materials. Dottedpart and gray area show the distribution of muddy ash and moist area, respectively. Maps are based on + :+*,*** volcanic map of “Kirishimayama” published by the Geographical Survey Institute. Contour interval is/ meters.


 

,  +/(,**-)  +,   ,ῌ+   ! +.  " #$% &'
( , )*+ *,- +** m ./ 01
234 5#  -. 67 8 

;#/<=+,->  + 6?
   ! @FG

C (,**.) !

H +/(,**-) ! +, i +, :D 5++ > +. 0a7

E23&';># => ?F;G?

 ! +/  9:A 5&7 B )CD E

+TH , +, i +, !I<Cd  

o3J#K'KW3!4/<C\-f<

5#  , 67 Lw o3M dN

H +1(,**/) !I"J8K"LM#!N3-<C ?- opC4$ ;4/<; &B!OOBPQ;$C3

! O +- P 2 > ./ 0 pC,-KN3

RSBTUVW3XWK &YZ

}pC (*+4B>!)4 K

B%&'[C\]=+!(^ _KN3

; :O>;#/<>+N3Q&!)`a*+>, ,bC;-=+;.

>;Np, D>,-R;

-<C3 5*c +3+27

d,,e-f$/!g

0 '[/<C =h12K!

H +/(,**-)*] +, S,- +- T ,bC;'KW3oX p¡U:;.

! +, i +- " jk+ S.l8+h+-  (];4Kx7! &'mO3n opC)-

 N3¢R£¤ 5¢V +32.7 'W+,+p )`a*+>,B45O>q6

X£¤¥Y0 , ¦§KNp (Fig. +a) =

C 23++d TU )Cd 23 8

>r%, ¦§,-! Z¨K*,- +a, m ©[K

& d+sC RtBBu; &dª«¬\ef ef,]­¬;23QKNp

Bv wXx78b-<3,V ®¯!^] -**a.** m °w[<\ y93!z1 {:| }p; ;~_'Kd A± D +X`$²a]=+;KO2oX <=!(=K,9 !

 +- &0³b´! µ¶KNp;

-; >  8 y93 ?@A;B

'W<b´!· _¶K !*,-

+ !   9

'cY ¸pC01C #¹º
?F! P 3 >daS - > $%
;

ew»?>u!h-<-

'CN ,**- e +, *»/!f¼H1zg

/

477


   ,  T2 

T3 !"#$%&'( )+, * +/ , +)-. 

/0"1. 234 5 352
6789:;<=3"- >?
@ > )
0

/A+

,  1  T+, T

T1 B. CD ;EE/ 2F

,ῌ, 
T2   /* cm G -H. 0;:D2 T3 !!IJ";F "KL#;$MN!2O%;KP&P @ /H+* m 52'Q R2S3N!(QT(UQ
7 .*V !W83 5 :(X%) T2 @*+Y';:7!

2X"
T2 %,Z +/H,* m 52G [-P. \[P!-P/0] )"93D^12_ -cm . 3`:45;ab" [-P.

 T2 6"%#7b"D;8ac%9"4T:;=3D2F
N def@<=MNgh%&i'@9 >jkl2mC": O+ /0]T2 

2?nop"/0;q=:]!:

@r=3D2 >jkl2mC"NDDF (Fig. ,a) 5 67qsA2FN; T2 @ 4;?tB"+u +./ m v32wC;F (Fig. ,b) 4 T2 @ + m ghB"xD2
Eyz ){| , z?}. ~FR2S3N!;2
:"ghQ2 GrD:" 2FT2 @8arHO%I#JD:7 K'

8aDeLM:"d <:#NG%OMNP2F; L 2<Q:G
 +,,** m, 2F (Fig. +b) RS% *.+ cm!TMN! rJ +., m !:N 5 T2 @v-

324 U= +./ m  /* cm 2 RS% +* cm!TMN! (VW *.+ m- !:N 3&rHXJ , m- 2 fVDD +* m- %
M!:"2F#

Fig. ,. Features of ejected materials. a) Rounded
accessory lapilli coated by mud and crushed clay
lumps that were observed on a large rock at +/meters from the T2 vent. b) Extremely
small-scale mudﬂow poured out from the T2
vent. The photographs were taken at +. : -* on
December +-, ,**-.

T3  T2 !Y "KL#;$O%K

P&P"  T2 !!IMN!J"+x

EE7 T3 @¤¥¦` RINT,*** %§a X \¨©pª2,ῌ- .E458a:%¡L X \]%¢£ X \]_DbP« CuKa \%a" cT¬­ -* KV +.

T2 @8arHHZL%[Nd X \mA ®¯°¤¤°± +ῌ,² ³´µ¶]% /0]\[P!-PD;¤°± +ῌ,² ·¸¹¤°± *.-² ®¯7b 330%^(0CTºd# ,²2FNoºL »pq¼_»rrst

478

Fig. -a  Fig. -b 



X 

(Fig. -a)  

     !"  # $%&'() ) *+,' -.+$
 +* /ῌ012'() %3 +* /ῌ012456789:;<=> $?@AB%CD%)E ,**FG;,,) G;HI

JK +* /A 1 /L,) M ,**F G +* /AN,%(J+O& J +* /A<P* +* /ῌ01

2+Q 
R   (Fig. -b) 
'()

S



 +  !'(  T +U$%( *+,' -.O%C'(  +* /ῌ012'(%( J&*O&!"+ VWX#$(%&'Y<Z['\(Q)!+)Q  ) *N]^'+,-(+* /ῌ012++!

.Y# <_ (  +* /ῌ012'`a -(

J+!  U?@/4

B('Y ,O\(Q%(J+O& VWX
#$(%& bB('Y<Z[)O Uc0
*N,\(Q)!+)Q 

Fig. -. X-ray powder di#raction pattern of a) the
dark part of the ejected materials, which consists
Al : alunite, Cr : cristobalite, K : kaolinite, H : +*/-halloysite, Pl : plagioclase ; b) the white partof the ejected materials. Peaks indicate Al :alunite, Cr : cristobalite, K : kaolinite, Q : quartz.

J]> 1d2eVWbX#f& U!/4$%

g%hi3\<\(,'(%(J+O& Jj8 4h+(>]Chkl56%m4+(n]>

%op

T2 $(%& 'Y<Z[ O Uc0 *N<E hkxV<W  X J<Y
J+Z%[+% }

JO&&O+%^)hk+,)L('T 

Z[ O,'\(Q)78 hkl9(-ῌ+   :,)J+ 1d, )q )!+)Q X\] ¡E¢£w¤¥¦% K

%3 /4rs; C<YYg=Q

hk§

 J¨Q ©3^ª g=

%O^) >tuv?wxy,)@&AHI B( +/ ChkzD{EF +. | ] + 3}G%~
9~+n& hkl(&Q'( %(hk+,<«¬W J+   ,O, J_` h6-­ ®abLg
 J+cd+%  UJ

JHe%L,(O ¯f%fC°g)C±@,)
- 

UHI ?I (+3+2) V²h (+33+) PQ'(

H<h ?I +3+2 % JO& K +-(+22*) C 3 O&?L +,(+3,-) C 1  J>p $%+!³´µ. h J

 He¶C^)J+! ,) H<hki.* C MN-h<CO,)J+P

jF - k V²h ,**/ lmkh JR%

  ), ?LQ n·&d¸]CL,(He¹Q'( ]>hiX# hiO& , km RS T},)?
hkU g=

J+ %( U)d«2Aº») ,**-  +, 1M ¼ ':®+ 2A¼-ῌ+ῌ+ ,2(+23/)  1  +0   +* +0 

Y^ 8sA

,2  +, 1 ,-  '6` 2  (+3+2)     


7





 



"# $%& '()* +,-./0 1 1 +0 230456* 7(+230) B "#!&C D-1 

230456* '+T : ,3(+230) d5q!0 : ,2(+23/) =+6B',-@*-ῌ+ῌ.  -,(+233)  1  ,2   8  -03, 9 : ,2  +* 1 +2  0 ;
<= +* 1 2'>-6)* ?@ A -1.1 9 : :')*=c;

=()* 7 ,-./: ,3(+230)  +,1 +2d,+ 

!

479

2

,2 

  (+3+2)   .7
$4A_nfg

Z{e! 

5!EF"G1H!@)B: :1GR342 '()* +

MNOP).

 3 1 1 42<>-6)* REIJ#'KL$%&4Q' R '(! (S0)*=;

 (+233) 0B;6')*= 2 1 ,2 <=()*  '+T 1 1 +0 UV G '2'5b6)* b 1 1 ,2 d5q!0 2

 W!XY@B0 +* 1 +0 =+6B',

1 ,2 =+6B',-@*?@ -?0h-@*-ῌ+ῌ,  ,3(+230)  0  ,/,0  0  ,- (,**/) 5<>-65

6 : ,0(+23-)  ++ 1 ,+ 

24@@ 8  -+,, 9 : : ,0  ++ 1 ,.   -+-,

  (+3+2)  ./ Z
0 1 .7 [\#24@!

9 :  +, 1 0   -+./ 9 :  +, 1 ,+ * iY8
 -+./ 9 : ,0  +, 1 ,+   r k++l 1

MN ! :]1 ^342 '(7

)* _5 0 1 -* 420

C kj + kml kl5)B!7ms}

26=780GzX ' 22O

456= 0 1 ,1 42 7F9A

kj ../ ml $ilN5)Bn\Jo E '6`2p' !l=  .] :;<=a> 0(b@'=c>-6)* ?@ ,-.
/ 0 1 ,/d,0 

230456* 7
Bf+@

Y7q/G:(!Jr5)

25!4 '()D`  2stu0(b@* >T + ,(+3+-)  . 1Nu 2 A

0 1  . [A 2@e?@ +30* D` Ct5/'<>-

gABCh_DEFMNGHIJ$i@)j

656yiB()*

 ;!

@+)

(! 8  -3*- 9 : : ,3  1 1 -  K1 k0
1l / ZA0+ .

7 [\mBnoLMNOP)=$4
) 4: : ,3  0 1 ,0  '()*  '+T 0 1 ,/d,0 

pQqb 2'@B0 0 1 ,- =+6B',-@*-ῌ+ῌ-  ,3(+230)  +,  ,+   ,+ 

uv;w`

 Fig. . zc@* ( z2{ ¡| 2¢v2£¤=3>-@  }¥¦§ 2D)¨©L J~0;w@t5Efvª
0 2;w Bc@*-ῌ, 

 +,Fig. . cD` « 2{ 7{05¬t­6)'=

  (+3+2)  r): 2@)
A7 v0,6) 2;w 6txy

7 st%#; R

2+TT+'5b@*
-ῌ,ῌ+  +-(+22*) 

S4 T U VJxDMN(!@! :]: ® +I

2 : +-(+22*)  3

1"] W42 '()* +y

1;w@ 8.: ,2(+23/)  +, 1 ,3 42<>-. :  2)¯!°-6)* ?@ : ,2(+23/)  1:5!'±² ³D +3+/ '6- «'780

ZzX7 ;YZ[4J{\]E"7

7 st%Y^|A_D`7 a}bR~+T)
-! RE +230a K k+, 1 ,+l 4)

 +-3- 9 : : ,+  , 1 ,. *2 j ++* .) 2®3(+11+®+11,);w6)*  2 iY : k+11+l´G1   sD!!Aµ«
6   6

²v?

 ¹ 

¶)d·OdῌAd¸W ¸

N²!&

Fig. ..

List of volcanic activities during the Meiji and Taisho eras of Ohachi Volcano (M : Meiji era, T : Taisho era).

480 ¯T=, ,** c)8F#1 0),F#481

 +330)῎{|)U}0< T=),~)ῒ

  +2-,

7(-<:) 70-:n0   +3-/ !"#῏$$ %

<* ]7 ]#Z0< =>()

    +,$&'()*+ ,-./0!
,)!ῑ 3(+11,)1  +-(+22*)

&,*0+-8F#$><!R- F#2&)

$ mN&aR$"($K3- 45)#῏$67 0(),c- JF,῔9, ]wA

089:;!<=>?@A<!!*) BefghK,))$+ 2R ,3k

+2,2 ; C +2-0 ; D +200 ;

--

++*

! +213 ; "E +213 

13

_P2&E_0<^+  8)=>()F#$$A<!*)mNefghK,)3)jmN,98F#]G +13/ ; C% +2** ; &' +2/, ; (H +210 ; I

$7#Z*&q+ A>     )+2-0  $J60<! )KL+/(+2..)- *+,-3 .M/M01N&O2
R(-/,345PQ I% 67 8& !R,*qSW]

& )OE_7q-

<0<ῐ|>|  +3+0 4}) ῍n M&0M1)aJ +330  I%67(

E0<-



 ,(+3+-)><S T=),U-I>?@)&O2AYWK :

,

(> )#Z-,[\B]$7^CD$I!

N-0];<j0<!

<P9:0;

R( V ')WX)"  +-(+22*)

2&) ++*+

 )}-0+

2  " ,m3- T)" 1 0)4)T=)F#-

=),F#-E_FG`&aR$ 8$F#t)c]"ῌkFefghK,a<Fb3*aR$HIAA> w)3jmN,98*J0<!

-ῌ,ῌ,  

R 0(0 ,2(+23/)+*),]0< ),c T=&-8F#)F#- JFaJF,῔9, ]$FJd0 efghK,$LJ7"aR

wA,K 50 ,3k-^+ mN

 ,+(+222)-jA+a<!aR +-(+22*)3i- ,*0+-8)jM 3k@

lmN$nO&-(aR Ro0 PQp7q-ῌ,ῌ-  +,  (+3,-) -RSTU0JPVr7q-Ws7Xt*)m

 1

(Y0

uZ[ +/.2 v :  ,+2,/  " ,)3kw)mN-xῌ$aR ,,(+223)

1  ,1(+23.)+,y  ^+* ,i- \]_P)3k&efghK,]z`0R 2R aJF,)3* F#-{b0<>| ]q*/.}cd
uZ[ +/.2 v :  ,+.M}]7,/  nn}cd2})ΐ]Pj e[ +302 v : e ,-+,-0)),- +,(+3,-)

J0R (¡8B (+3,-) L 1

1

+ 

h# #]¢¡0<o ++ aJF,$J
0 +- +. h# +/ +0 @l ,* :$A
<! 0(0 +.1+3 -£ &aRR 1),)¢£I-&w)T=-,0<!!$ :+*1+*_P-99FJ8F#]k<!R$ ¤0)¥5¤~¦)#῏$A<! f/ .M};;g],h#~ΐ]Ji e§¥ +3,/ ; ¨©ª«¦ +3,0 ; ¬o +3,0 ; ­® +3,0 ;[ ,/,2 v : e ,.

,  ΐ-nf/8&}¯°  +3,0 ; ± +3-* ;  +3-- ;  +3-- ; ,+  !aR#Z% +3-- ; j§ +3-. ; ~% +3-. ;  +3-/ ; ²§+, e[ -+./ v : e ,0+,$L7 )Rw)i- efghK,)3*

+3-/  )KL (+3--) - ,U³)n¨n1 }_P)jmN,*0+-8F#$©(:]J7_P&$:ª<«_P]Fk0<!R!K;<¬  2R ¤0)­®¯°±² ³y±k+ ,2(+23/)+*),;!<- ´ ´µ µ¶¦@l#·³¶®·* ,U¸](+230) a< }lm)Dn]7Yo)¹KR8]¸$0R*)$67 wQKlmp-q )E_F0<0-O&q!$rd0s0<c)t-u:(0 #Z)1+*A 2&) v>]wL0 :) ]

<!R^CD$I!

7Yo)lmuLx ,-a<!
R$yzA<! 2R (+230) - )i +,(+3,-)1

c- ,U¸]¹K_P)8F#$k0

A>w)- F#¹º]$0R#῏*'»+ ¼8F#*º><!! »¼  '(°º»±¼²»³´µ482+3/0  









   

-ῌ-ῌ,    !"(#$%&'-ῌ- 

() *+",-ῌ-ῌ+ t|(TA-%%

Cuv>:,,?wpx : 6 -0  ++ 7 ,3 #Q %4$9+ a>

:#
tu

)+4$%

6 ,3]--(+230]+3**) 6 -0(+3*-)  %L t

-8I

#- ./0++'123 

6 ,2(+23/) \

6 .+(+3*2) 6 .-(+3+*) |( " M38# t:: C)

5 6 +-(+22*)  3 7 !8 9:;<= 0>:$ ?@"+-3- A : 6,+  , 7 ,. # B$%%

@"

CD&E8F'()G*+H8,I(yz{M|Se%L /)z{}bL:)e/j%L e//]DPbLX~EcR ? +3*2Q Ce/)y{S0D%L# )

-.JKL8MNLO8#/-70#

}bL)e/%L# /]bLX7E,P-128Q +%9+) "LR ? +3+*Q +(_>:#6 ..(+3++)  ¡>:$¢

M3R44$%&'S=-T 568 6 +3(+220)  +*77U

V>:WX YZ>:$ 9$"8[9:  +* 7\

 

£¤

? +3,, >./i  z+ 8#L (Fig. /) o$./)~

568 t¡¥:

6 ,+],,(+222]+223) @" :%% p8}MP)8- i,;^(_>:$ (Table +) 9:)<=R 9:)" (+3*2)  (+3+*) (_+ `aRb' 3 >cd: ῌ +-M8#"e?@TA3 BfR9+C 2g8

9b' i01¦%%

6 ,2

1 +* ChDi>:#$ ῍ EC(+23/) \ I+-6 .+(+3*2) oe7U 0>: 8j8jF  £¤ ./ 0>:# n4#

G8

klkH Im8$ ῎ =nJ389vM

KLR9+-%4$ o$-T pq38)qP./w+38#$b'%$ ῏

F L o$?@rE%s§ 6 .+(+3*2) Cz

ER j8 e/ )I¨b'4$tu   UT])8 vM-8I TA

yZ:bLy5~E-T©jIl

NTAwxO8# Ry 6 ,-(+23*)~ª# ,IR*+R e/} - 7 CPpQ8#RS8z1vT$- C#8#3R ? +3*2Q +%LU  V b L  E  5 L R  ?W  +23*Q  6 ,2z«z ):$(+23/)  +* 7 +0 #u"+8# C{-X-ῌ-ῌ- EHUTMPY^Z|R[+\-]

./ i>:$6 .+]..(+3*2]+3++) ^}H_%L#/ v+8#-` L ?kC¬6­ z® ¬+3*.­ bLe ¬+3+-­ z

5 +230Q Crabacde-8

I¯8M#~ Df)gTVUV~

+3+/Q +%b' ( 1¦%$ te-` cR-%LUVMhu",# e ,(+3+-)  . ++¡-¢L ?e£ij8 TUkc8#lmn+, 7 ¤ + 7° e -(+3+.)  3 7TVo`8$-j8 ?p" : 6 ,2  .(+3+/)  2 7  /(+3+0)  2 7 +* 7|++ 7 2 #Q +%L( %)q UT]w+3

8# 6 ,-(+23*) 6 ,2(+23/)  |(t#9e -(+3+.)  3 7 C¥bL±¦y``L§ (conduit) %L²¨©³ª ?>´«K¬

vM-8I TA  UT]z{ #µcVp V¶·R ª¸H

 T2  T3 }r%4$st  T]%L/­bL®¹#¯$:%
Table +.

,**-+,



Description of fumarolic activity within the Ohachi crater before the active period.

483

R»S ¼TUVW

484

Fig. 0. Photograph of Ohachi crater taken in October+3+0, showing that the small central cone in the
Ohachi crater had almost disappeared. Photograph was taken from the southeast crater rim(Oda, +3,,).

"sFig. /. Comparison of the topography inside Ohachi
crater. a) photograph taken from the east
crater rim in ca. +3++ (Oda, +3,,) and b) takenfrom the same place on September +/, ,**-.

*>

/

(Fig. /b)C  l# T2 I T3 =# *$ *|9s xC
;0

#;<V

 

#H># sK  /(+3+0)
 +3++
 .(+3+/)      +3,,

2  

# $%&'()*!"+)*,-

E2+3#E|9s  }~l<*:.#;.ns<x/ ,-(+3+-+3+.)#tuE?dO0E

nstu#7E{8:#s%C n:   0e#@'{8*#Zx A<x:C-ῌ-ῌ. ῎ῒ῏ΐ῕῍ῑῌ῔ῐ /(+3+0)+* P## ' ./0 $1234 $= (+3,-) <CX (+3-*) EC

5 6758# 9:;<=>B  = (+3,-)   +,(+3,-)#? @ A3 ## B +3+/ <%C /(+3+0)

2   <D $

9:5#EF/GEH 58 !I:J#KLM$#&"'#+3*N$% #.OPQRS:0T BM&

%E *

 B+* Dms

1 #Eg# 3Ex:7  F 1 # P#  A3<]
0C ; "GH#HI<x
E% ##&4E% b)*¡¢£ ¤bJ 5#¢£K ¥-<+

UVWX + XY+.2 m #. R#KZx¦L§s% <%C :\¨O0x[\/?]'T(^# )% B +3+0 *qr op,©M s l# T2 I T3 =s#+*  +-Z _`,ab#c7-d. / 0e1 0f  2b ]:#g/hi3>jk:c7
4-d+-[ 0e10 l*>I *$|9s xC
CX (+3-*) #qr op,©M s  N&
4ªOtuE«O0 T3 <*`¬PV*E

­®]QRx#E|9s

C n

Q 5m64   +3,, <%C n:  /: qr#¯° E  #>jk©±²

+* opO0:qr   +3,, s ³ >©´µ¶·¸¹> m Qºop(+3+0)

tuv#7 wxyz{8 (Fig. 0)  <%ClxQ Cfg ,**-  +, !=(=c C

 +,(+3,-)  1 







  +,(+3,-) 
1 !"



#$%&'(+*) * + (+3-*) , 
-./0

1/234506

78 #$%&9 *" :; T2 < T3 =>485

[" $=jst8 , km
+bS KC2 +230NO  -0(+3*-)  B
C{|2!`r_u}2=~T K^$ :  -0  ++  ,3 "NO =C/ C g-e

T8"]0_ ]d"b;Zu  -e=]d$7= k3,< N(+3,,)  B #8 B O `$P

=?&+@0A-ῌ. 

us +3+- sr"9:]0S=W¡O :  ,1(+23.)  ,  BC

=-.==  ,(+3+-)  +, D !E"#FGHI$$J KL%

]dMJ C"& -,*. M :  ,1  -  1 "NO  ,2(+23/)  +*  ¢£0{¤=0 C/ C!

 B'()=PQJFR0:S$$T/} =^$-A L%<s¥06-*'(+UV"S#SS=WX6".780= _ -.78"¦0,-T./%Y)ZQJ"[081 KC2

Bd  -e$Z= !

+230NO =3 45 \=]667780

§$¨J -eMJ C/  8-# ^-9:=0-. \=]6:$;`T8:<ab_!(+ =+

 +*>_=" ,(- =+?@A3   ==#$;= S c
Bd # (,* !45)Z3 =CD+efg+E=hF  ,7 J

Fig. 1  `C!©ªVm! c9=(=c]d=MJ C/ C!=}"Fig. 1 Z (=c Z} +./(/ m ~C , km 45 g

(+3+-)  /  +3 "(++ *i+E KGc8;C|"«f

+3+.N =

5 

2 "N

K ,  ++  2 " +,  3 " H + 

FA3"c8,IT"j0 kc*  ,(+3+-)  .  -l+"mnop+E  -(+3+.)  +  +, "q':JZ06rKLe+E/

06+s: F<:JtuMR0=v
" KNOlwP ,**-N0kg

k Fig. 1 0

 2 km 1CgA3S!¬A3 ­ 0 M




Z¯

 xQW¡ y{kT ¡ ®¢kT
f 

g!¬-e_ 1k£¤ mn<¥¦k9ZkTX!¬-e"6u8 S1k!¬A3

xQ  l #lCRST yUVz{<W XYZ|CRST 2 km 4

TX!¬/ xQ-ῌ/  

0_="Z} cm 45 C gZ} / m [Z~ C ; c8 C

= § (+3+2)  B -+(+232)  y¨©ssª"!¬SO = #ª" L%& +3.1 M K ,,  +,  ,- "N  B \(,(+1+0(+1+1) ]^_| 

+,  "°«=±!¬-²#E K²#³´E^_|ῌ\` KalNO +33+N 29b;Z­®0SN .¯1_³i,[Ou xQ(=c]d=  B -+(+232)  °C©ss±"°



s=

-e"  ,0(+23-)  Bf`$g. § (+3+2)

1²³JRI³´$XO G(+3+/)  B -(+3+.)  ´"°s=s!
¶*9:Zµ9H

CPnPo$p KL%& -+-, M :  ,0 

¤ o¸¶· ¡ ·Ca<¹1_>n¸"<+,  0 "NO  ,2(+23/)  +*  B]

¹SO =-. 

  

kL



h$i j . km Uk<XSlf`Vm¹ c/

S µ ·[ P £.qr.7>}st8 , m <"-ῌ0 

Suvr]wS k9Z

 ¹£=C/ Cº<x T1yN$zS. "1J0¹£=ºº<§O«f

C¬»»d/¼

Fig. 1. Distribution of ejecta in the Meiji and Taisho eras from Ohachi crater. The solid square with the number represents the location ofballistic bomb or block and its maximum diameter (in meter). Descriptions in the rectangle are taken from historical documents (the number
in parentheses gives the eruption age (M : Meiji era, T : Taisho era)).

486 

¼#;`r ,**-  +, b$-



487

* ;:&'9    ,2(+23/)  

-1*,  :  ,2  +*  -*c! .9; C TgT-/TgT-++   ,3(+230) (=9 VD! 99   +230b  ,3(+230)  

:[,  mm c?ΐ

 +3,-  --(+3**)   :  --  ,;vA !,9 ,.

  +,(+3,-)   :  +, 

1  +-+.

! .

+ TgT-+TgT-++  C῍;c VZ  /  !"  #   C  ,2  : -   ,3  : +   ,3  :!;ΐ uvZ$+   +,  : +  $#! ! %&'(

% .$¡8 .:/; TgT-+TgT-++ )  --  : ,   2 ! "# *+$¢F £G d$ $,$+,    -  ' (  .  / 0   ,3(+230) !%# "& 1234

&!5'67-8 9( .:/; ῏()*<)!, (=9 >

-¤$j¢Fd
¥ 8  $%D/8
¦-=D L6!§$^@A! 

!"( .-¢ 1( ><+;B,A( + -;5 .CD

=$, VD$',9§<N<,?;( ? !!&E" F /'091,?GHI!8& .$ C '( .9;'

!J/- =D KzT, MsT, ThT  TgT-+TgT-

K  LMΐ?NO)P;2/B?3++ /0 J¨¡¢r5  TgT-, !

4Q567$'  ,2(+23/)  R

= +*/ m- S TU89V ;'5:)PW+BX;<;Y=Z,**. . +- +*/ m- 

[  :  ,2  +*  +1

P!& $9 9 ;E8[\  ,(+3+-)

 R>?@A:[];B^CK!Q5D
E"H_[  :  ,  +,  +*c'(   4;&'(.$¡8\ [ FG'(' `8,(:/. 

--ῌ$>£

67 1(
a@ bc;:$'  ,3(+230) ;©8  ¤.$¥ª9

RHIdJ;Ae1,KDLf g hF«'(,5'¢; Table + ;¥MJ;NO [ijPPkQRlSmTR

 :/; #>¦d)U8!

UVc +nWS῔MJop;῕)qX -3*-  :  ,3  1  -G¬'(­U8?§¨;© 

\ RYKDZ[O

+ 98&  F«$$ ;>®HM

 \r]^_s `s ts uaP b 9ª«$HU¬PG¬ ^­>¦_`®$vcd$[)eeH;fw'xgxhy zi\  -0¯$yZ D¡05'¢;U8©° .

(+3*-) ; R{j|k;}w 34lm,bc

$ ª«D¯°¯;±%D²4ª«³

 :  ,3  0  -*.9  ¯°¯ª«;± @W+;~9  Vno,pq.r;s"K῎9´!& .$ ¥'( K  ¤ ;¯

, 9't@;uvῐwῑῒ xy)$'z {°¯>¦;<µ,.$! >®HMª«$HU

0/% '|qX Z+  : ¬P ²" ²4ª«³῎ ³´ 

 -0  ++  ,3

!J/

$[$

\ $[ ῏}~G;1,¢'¢; >¦_`®!%¡9 '(-ῌ1 

 ^­>¦^¶µ$-;`r-ῌ$K  $,$ a-¢>¦^¶µ;·¸,  - !9 VD9 >¦;¶N =@ ¯°¯·UL,¹¸! TgT-+TgT-++ `:` +-**+1**  ;9'(`(' !" 4 ,**.

$C!©«'(C TgT-+

TgT-.  ;:4.5 -¢dCC º8 ¹,$

F»!ºF ¼[» F a,»«5¼±¼,©

488     !"#    $% &' 

2V L/<=   W&?
* +1(,**/) @aP0$/ bWc&)-

 &dv)  ?* +/(,**-) @ +, _ +, A
rs O%   2$$efOw,V2

 & (%  )*X[-?) 45 +,(+3,-) @rs2?$/ 2*

+,-.  $% *@"&dv) < .x/ 0- %) !

7gy &/TzhOij/u& /1 '% 2  3435)

 K dv{| klbm1%2 6  7&89 %) 2V&{|n oX K*

1 *:!"#;)$% *+pdv`O }q72)r/TUV<= &'> ()?% @ *&<  niJ P0 9Z'  A  *) B*7+*C

AST? ) iJ? *~ [%D5,7%E *+-F.G  H

W=/T  dv !6qs twt u&J v=%E *~ [%I&J)&'7> ?%
K L/* T2 M. T3 )N*? ) O% 22  P0*+.Q )  HI)&'71R
S2 %%E/TUV %W34567
  X 7 K343)&'!

W=/  c wiJ/u  H
Ixyz&{xV&P9 h72X[-? L/ @" | } Y)b3  4567~Y}Y/T *p LiJ/u 4I)T5)*FY2)T?0  HI&'>?0 }q &i,-l)L/*+&JZ ?  &Jx?7)72X[-?/    8\]^ 9:;<=> 9: ?* +0(,**.) @ + _ / A

 T2 B/C%& - `D

)ZE? a?* +0 @ + _ +3 A bFG
c =aL/ded - _ ,0 A  2?$//H 6" a,// I ; fJgKhLMNd  OP
)iJ?% a?* +0 @ iJQ +2 jd $% T2 B 

 R@ - _ -+ AST?%P>iJkl a?* +0 @ - _ bFG

c = edUV/  W& / `D,-&' Vm[ XY- ?* +0 @ 1 _ +0 AP>/niJST T2 B

A)W& 1 `DT

2 ZE% ! 9Z  3 _ 3+- A ++ _,. Ao[piJP>iJ ST  \)]q1

2

++ _ bFG(,**/) @rs^% a?* +0 @ 3 _M.
c = ed - ?* +1

 - _ 3++ AM. ,-,/ Ao[piJ)ST?  \ _@ 3 _R t_@ - _R/T2 a?* +1 @ - _bFGc = ed 3 _ ,0-* Ao[piJ/ M - _[p4u&`O ZE? &2)^?% a?* +1 @ 3 _c = ed $ET%'  pY

bFG

@

M. c e ~ &hu p

4u?$% $% #|#D  T%q& ' u$% r&q,- %$75 (+3,0) =  ¡  ¢ £¤¡ 3+ῌ++..
¢¥ £ (+213) ¢  ¤¦>§¨¤© + +ῌ-/.
+ 9: (+3+.) 9  +1+ +/.
+ 9: (+3+/) 9  +2- ,+.
+ 9: (+3,-) 9  ,2. ,*.ῌ,*/.
n ! (+3--) =} ¥G "# = aAw
23 ¦d §ª¨ -//ῌ-1,.
8«¬@ ©$­3®%&ª««¯ ¬¥ (,**.) = <=°­iJ±,**- @ +, _ ,**. @ + _ = L// ®%OP V°­` >²'¯³§´§¤ ,**.
@R4¤(µ v*//-p*--.
°±²¶ (+2/,) ³)@  2. ´"µ¶· (+3-*)   >*§·¸ a>*§k .d >¸¹¹ -0 p.
º+º (+3,0) ¢ M >» ¡  ¢ £¤ ¡ /3ῌ11.

A=FQSH ,**-  +, º» ;°@¼x
 (+3+/)   -, 1/0ῌ10-.
 (+3+0)    -- 1/*ῌ1//.
     (+33+) 
-**    -0 +-/ῌ+.2.
  (+2-0) !"# $%& '
3 () *+  -3+ῌ./,.
 (+2**) ,- 0 
ῌ! (+3--) "#. $% '/23 01) &2' +,3ῌ+-..
345 (+2,2) (6 789% ')* +,
-.:) /+-ῌ/,,.
+7 (+3,0) +7/ +0 p.
;01 (+33+)  23 ' , 4) -02ῌ-11.
;01 (,**/)  23 ' - 4) /,.ῌ/-0.
 56 (+3-.) ,     <=  >7#8 '!9? #:;  , *) <& @ +++ῌ,+..
  (+32.) A=BC D>E?FG
H#I J@ K4L +**ῌ+*+.
 MA N (,**-) BOPQGBCRFQ
SH % B5D TU VWEX -1
,ῌ++.
YZ[ \][^ (+230)  K_F`G. ;abcHdefghijkZ 'IZ) #.JE 3
-.ῌ01.
KL+ (+3-*) A=CMG# Nlmn #:@oOP* pOq +3..
* r56PQ*6 (+3,-) Ystu vR
 +*0 p.
789 (+330) wSx&
789% '%* T /)
3-0ῌ330.
789 L (+3,/) U3V$%(yW -* p.
XzYZ{ (+3,0) yW [\ + ]W | (+3-.) !9}^!<_`~ 0. p.
>  (+210) pabJ#: '(V*) 2+489


cde (+23*)  #  , +12ῌ+2*.
RfD (+3,,) #U#. E& 8gh
 LEX 30 +ῌ/2.
@iv (+3+/)  Fk-, 0+-ῌ0+0.
@iv (+3+2)     'j*) 8
gh LEX 20 +11ῌ+3*.
@kl (+213) !9#m '(V*) ,, 
 n o (+200)  '  ,  +,  . )pq (+3+*)  #  ,, 1++ῌ1+0.
rs tR>u (+3/0) vwx (+3,0//) FQS
H #  0/ /1ῌ/3.
 B> (+13/) Cy6 '(V Uz)Cy6
& ,.3 D{q 2,ῌ3*.
< | (+2-0) *P}V6 $%& ' , () *+  01,ῌ03*.
~AZ (+3--) #% $% '/ 23 01) &2' +-/ῌ+.,.
~AZ (+3-/) VW 789 ¡LCR9¢£
L -3, p.
J# ¤L (+230a)  #  2
.0.
J# ¤L (+230b) E #  2
,+0ῌ-+1.
J# ¤L (+233)   #  ++ 0.1.
  (,**.) A= ¥¦  L ,**. §¨@L©ªg«&+1*.
¬­ (+3-/)  8 'h? ,) i +3/ῌ,2,.
®+6 (+3*2) "Fk #. +/ .-*ῌ..+ .1*ῌ.2*.
j¯6 (+230) °l±±²
E #  2 ,3ῌ--.
³´¯ (+30*)+3+-  .  , Fµ¶·>A=F¶¸  . /*ῌ/+.
'*& 7¹¡)