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

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Reconsideration of the +3** Explosive Eruption at Adatara Volcano, Northeastern Japan
Akihiko FUJINAWAῌ, Takeshi KAMOSHIDAῌῌ, Atsushi TANASEῌῌ, Kazuki TANIMOTOῌῌ,
Youichi NAKAMURAῌῌῌ and Kazuo KONTANIῌῌῌῌOf the historic eruptions at Adatara volcano in northeastern Japan, the +3** eruption caused the worst
volcanic hazard taking a toll of over 2* human lives. Although the eruption was thought to be phreatic, detailsof the volcanic events have had remained uncertain. In order to reveal the course of the +3** eruption, historic
documents, particularly the reports of newspapers published by three local newspaper companies, were reexamined
and mutually crosschecked. By correlating the revealed eruption sequence to the facies of the +3** eruption
deposits at outcrops, characteristics of the fatal blasts that accompanied the eruption were examined.
The sequence of the eruption is revealed as follows. (+) The ﬁrst explosion occurred at +0 : ** of +1th July.
Because the explosion was very small, all the workers stayed and kept working at the sulfuric mine located in thevery bottom of the Numanotaira crater. (,) Immediately after the second explosion occurred at about +2 : **,one boy ran away and over .* workers commenced evacuation toward west. (-) When the workers reached thewestern rim of the crater, they witnessed the third explosion which violently damaged the sulfur reﬁnery andlodging houses in the crater. A small pyroclastic surge accompanied the third explosion which occurred near theeastern rim of the crater, blowing away the pieces of pottery, wooden sandals and clothes, together with the
housing materials. (.) Around +2 : -*, the largest explosion entirely destroyed the sulfur reﬁnery and lodging
houses. The fourth explosion caused strong pyroclastic surge and broadcasted dense ash in the crater area, andwas also accompanied with the wet surge which ran down through the Iou river. The strong surge hit theevacuating workers near the western rim of the crater. Among the workers, ,, people were killed and the others
were seriously scalded. Probably, most of the fallout ash erupted during the fourth eruption.
Characteristics of the surge are summarized as follows. (+) total volume of the surge was ,.3&+*/ m-,including 0*** m-, ,.. km long and .ῌ+* cm thick deposit along the Iou river. (,) The discharged energy to form
the new crater was +*+. J, roughly +*',ῌ+*'- of the energy discharged at the Bandai +222 or St. Helens +32*
eruptions. (-) The velocity of the surge near the old Numajiri spa (+./ km west of the crater) is estimated to be
2*ῌ+-* m/s. (.) The temperature of the surge near the crater is estimated to be over +**( but lower than .**(.
(/) At its margin, the surge swept straight up the side slope of the valley at the corner of the Iou river, anddelivered thin surge deposits at the top ﬂat area.
Key words : explosion, blast, surge, phreatic eruption)-+*ῌ2/+, *+,-. ,ῌ+ῌ+/012$2345678929
Department of Environmental Sciences, Faculty of
Science, Ibaraki University, ,ῌ+ῌ+, Bunkyo, Mito,-+*ῌ2/+,, Japan)++*ῌ**+. :.;<:=>?@ ,ῌ+2ῌ. ABCDE
FGDHI%
Sumiko Consultants Co. Ltd., ,ῌ+2ῌ., Kita-ueno,
Taito-ku, Tokyo ++*ῌ**+., Japan)-,+ῌ2/*/ J;K,LM -/*J;K12NO2342NP
Faculty of Education, Utsunomiya University, -/*Mine-cho, Utsunomiya, -,+ῌ2/*/, Japan)32*ῌ2/12 Q<,RS=TURS:>1212V$2WX9
Graduate School of Science, Tohoku University, Aoba,
Aramaki, Aoba Ward, Sendai 32*ῌ2/12, Japan
Corresponding author : Akihiko Fujinawa
e-mail : fujinawa@mx.ibaraki.ac.jp

z{|Y·¸}¹Y~º!Y}»Y}Y¼!

312

AB*f34+    +ῌ+ 

+ῌ, (pyroclastic surge)  +3.*ῌ0*  +/ km 

 B 

  (,**/)  !

s4 ^)/4$_`Z
GhQa bc4*M^>d1

"# +0/2 $%&'  ()* (base surge) ef @g+, 0 -./01 $Table +' # +3**

`>$ $Capelinhos  +3/1  Taar  +30/

$% --'  1 2 !34" #$ 56%7

$' #U,h (Fisher and Waters, +303, +31* ;&84'9():;<= 2* *+>?,@$Moore, +301 ; Waters and Fisher, +31+) B

AB*CDEF34 3G3$ F +, - (volcanic base surge) @ 4 F bh

EF84./" ῌH@01# $I2

" m^)/4 ijk Sj

J .K3L $M4 +3** ; NO +3**a, b' @#53P@U/4 ¡ (@30 j

QR6 7S>T8U/1VV@80

l80 ! ¢ £ (ground surge) (Sparks

14  +** -

!34$9W* 7SX

and Walker, +31-) ¤¥¦ (ash-cloud surge):Y;&Z[ $AB<=Y\A0]>^_/(Fisher, +313) >§84 $mg

`a bc4 >A4@#de@fgh¨ ©@S[#* dry surge,

i- +3** $Qj*k?lm@n;&3jn" +**ª op «¬34bq*­®#* wet" #$AB*UF@*C#@30 op

surge @¯ (Wohletz and Sheridan, +32-) Valentine

qr*s84 +) $DIGhEF.t*"uGH

and Fisher (,***) 

Cas and Wright, +321'

-=" #$

I3 &J*KvX:30$Qj*U ;&34V4b°±Krs1 hydrovolcanic eruption $

,) 3L.w/4LAMxGh $AB;

bh$¤¥bh"

NO*CD)3 `*9P34 -) `Q2J

±Kr1 hydrovolcanic eruption 80 ³´

m Ry$)S8Tz@ 8TMx*nU34 /h

CDEF/@301 ( dry surge,.) {|34 +3** $VWSX8Y}Z

~Z=P*sF@ .wGh;&/

*²' I=b°B wet surge >µt*@fgh
01 (Cas and Wright, +321)

4$t@ $)S@0K*hG34

VWS uv>P SXS53

V4 4. ,) @QbNO*[ F$nU

1 (ﬁnes depleted) AB> ¶w30[htGh /4\`W13VW] ( ^6 S@©@°xj $Syj ;Table +.

List of historic eruptions at Adatara volcano.

H +3** }Z[\ ¼]^
pyroclastic density current  
   (Valentine and Fisher, ,***, Wilson and Houghton,313

@ (Valentine and Fisher, ,***) wxhyz{x| +32* }.&[r!"#'fgNh= fgNh!"# (blast surge) ~,***)     !"#$%&' V' fgNh  ()* +,- $%./012 34,!"#&uDv !"#'

56785 !"#9&:; <&e- &'(!"#@= Wohletz (,**+) ' Wohletz and Sheridan (+313)

 Z[\ &uD

&>?3 !"#@ ABC&DE F G3 H
I

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Y*

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@ E$%@ !"#$%

®! ,/* me(ª :; «Fig. +b fgNh (blast) ' i@j3k5 lN
mnoBCp&`q[r s&t uDv

ª «¬­! +./ km,q ¦§&'"¯°&±²±

_#\ ¨©

-¦³´µb="¯°¶·¸¹&O5ºW »u +,./* m ¨©

Fig. +. Map showing the topographic outline for the central part of Adatara volcano. Arrows and solid squares
show the ﬂow lines and the existing outcrops of the pyroclastic surge (deposit) which ran down along the Iou
river, respectively. Solid circles and oval-shaped curves show the localities of existing outcrops and theroughly inferred isopach contours of the air-fall ash of the +3** eruption, respectively. The area covered by
dot line indicates the inferred deposition area of the pyroclastic surge at the crater area. Solid, roughlyoval-shaped area in the central part shows the newly formed crater of the +3** eruption. Dash-dot line covers
the area described in ﬁgure ,.

GHµg»¶d¼g·¸¹Ag ºg$»+g¼ y314

   +,-1* m 
 ,** m,  /* m + km   :    +,,-* m   
 !

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U6  +233a % ,/ ~ .}

QRSQPTGHG OK1T\6 L - K 

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7( ?W?]0 ?Q&%ª

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} R &} 1 «%&T\6 

U6 K  ^_`XYZ[U6JEK

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

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 ?j"c:% k®@¯& X° 0ῌ0* cm £7(¤®U 1*ῌ.** kg ¡ ­7(¢­

??@$+  .KlFm no?©1¥e  +233b    p"qr6 GHgsd ,**/    ± ²h7(  +*,*** m, ¦§ !

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+,

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 º ++ ¶ZºF+ +3** 
Table ,.

 »¼G

315

Sequence of the eruptions on +1 July, +3** (including precursory activities from early +233).

 

 +ῌ-   +0 #$%&')* ! "  (+,-./ 012
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7

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]$no}~p HYM2)2%

12;Q³PH7 oM ´> t7 1 ! q

+Sr%-vt  stu7L + &v- 2, &4&'QR+w t+ & @+!6 2

Q ) :  Q R $  ³ ag]Z9 ´ µ ¶ 5  wetsurge P+S [;X7

·o!$n 089 NOZ +3** z{| »¼¹(+3**a, b)  (+3**)      




  !"# $ 

317

8ZX|WG, yLD z{| }NG{
7 SC~68>jD QR8} ]^_`CD16 >% &'"()  1 * ,. +,- .-/01 2!

4p

ZX,  ,* Ou7>Xf34/ "#51$%678,591&'()ZXU6GnX>j Fig. +*:8 +, -:;<.':

cm  CD  W LD 1** m EUh, +*6) /0 1 * ,2 +  =>,UUh, 1 cm 1 U

?5&@"(A12BCD(8E3%(

ZMV45FG) /6 1 * ,. + H>

ZMV

L>Z

&#5lf

/** m l>Uh, / cm > 
1/* m῍+,*** m l[

xW 6 WD

E K >>Uh, / cm  VW6NV +./῍,./ km 
1 



Kf>, - cm   (+3**a) 

71,I8JKLD 9:M:1NG27"(8 (+3**) 1QR1 Z

OPH QRST6U, V;W,XY<=U, eK>EUh16 V> V

ZX [ E>?@\A1 N82! ]^_` ; !W(Uh1U 6G -3 aB CD1E."(cm (Uh>7(g,& V> . km MN ,LDFG271,OPbL H [ E@\Ic1HLDKJ"(GW 4(D,b=Hkm  Fig. +

 (+3**b) , +3**    71[1 ~dGeKL5 68 >MfN>Og>hU8DLD -+*0 T DRE

OPi, +/῍+2 cm /῍0 P Ej>+* m  .* [ῌ¢68CD1+£¤1W8¥+ m -

 , P >N8  +3**ZXQRSk,

0

¡>

+.,

-

[>, +.*/+*0 m- DN8 4 

T> l 

DD1¦ ;CD68ZX

eKLm >Uh, /**῍0** cm +1῍+2  ¥ [, ¡¥[LDeKLg[ E@\V 2** m 1῍2 W >,h" -*῍0* cm +῍,  bH

AuWCD68]^_`CD11W8

CD nX"(8 oV +/῍,* km YAf"ZY+*/ m- "(

1.0

l>*[pX q\"(GW  +3** / >]>, >+.0 km >pX n3 

X"(8 ]^_`CD1 ;CD1,*eK¢ U ^+]  _9LG`a6GW8b3cE eKLD7>@\AuW 

1rsW,&] t dD>,LN8 >,Lg NW6V][


Zvg  £U][WG §G]ff¨568
b©¤U¥0ªW6¦ªZHªCD11nX6

 +3**
@\AuW]^_`CD1v6G, 

8 o M> @\A«¬1K

l>, wexXyP pD +,§O ¨©g [WG£U] ]^_`CD1

fzgh fzij 7>,yP{pX) ª­O«1®| Uh/0 1 * ,* +  =>, +, k

68 @\A^¢¬1 /*῍1* m K¯ 0* m , vg°+*῍+/ cm CD11nX

 X1|| +,  

1 ,,.** m 6 ­±y²³j CDK¯U,l:1d}Gmno p"qn~r)h1 1 cm  @\AuWCD1[, ++*.

/6 1 * ,. +  s2!t

m-  ¥[>,X}D(8Ou>, +/ cmUh1NGW4

QL 78 
>

vg>fzil,.. km 7>,]^_`CD1

D(84 Fig. +

0,*** m- ¡7"(3ῌ+ !"#7 SQR]^_`CD1
Fig. + , eK¢NV{®´¯°±µ²~¶³´>q·68 Figs. , -a Lg>, +3**
 1 * µO£ Figs. -b, c, d +& 1

2 

/ m 1Uh>¶ 4´O£, ¦ª6

Z>, eK;CD68ZX1 4w

8ZXtZHLD¸·1 ¸lª¦ªZXLxq(G4 eKLCD6

D¹JCD1 ¶6GJ"(8ºD(<b¶·¸b¹ºbl_»ba_b¼l

318iRRcdj kClm1Dn` 'L-o%" pqrst, 'L-aE-+ aFBR =GuH

/`vbwIABuJxB yz{B-Q=3- B, C! B

cd=e!?,  | 6\74% ?, - KHn Fig. -d 0I cd=eaFB?,   , }~L-MNt, -
3ῌ, 

O0 8Pj - - Fig. + Loc. . /0 0/9 01 ! .ῌ+* cm

0^. +,QA
A

 8?, -+ 2R3'n STUf 3VW0^ XY0/
01f - Z[\]5 +, +.2 km
-0^ ^ +,-** m =eXY0 _
=A / cm#o z`9 =O ,/* m 45^ +,-** m -0 _aFig. -. Blast deposit at the crater area. a : map
showing the localities of the observed outcrops.
b, c, d : sketches of the localities +, ,, and -,respectively. Thick broken lines indicate theground surface just before the +3** eruption.

A +* cm CD`  _ +3** b#Mcde"fghi;<= `
9
3ῌ- 

jk 8P59- S  045^. l` 4!mn   Fig. , - 4*op^ Fig. + Loc. 1ῌ3  R

 !"# 8Plq Or$%&'($ $)*+,-. #  ?, XY&  KS-J_#/01-+ 23&'(4+=7,



A +*ῌ+/ cm V!-%V!

,  ..15+* m

6 ,.25+*/ m-B$ $ +,+  t/

7!,  

%!-8%!"9#$$% --:;<*%&'$%

?,   ,#$ @

C, E! ,ῌ- cm=>+, B, D

= 8Pv2w9 8$X? x     V{ ¡¢£, A +* cm G

0 A / m .H  I! B$;/01J 2K'L +ῌ0. mm
M=$NO
U C

PQ;R

-  AMS2T!

¡&'(de"fg¤@ 9=$% `9 => +*ῌ-* cm 7,¡¢£¡

 +.C by +/*ῌ/** y.B.P. 0^ Table -  +,

 +3** b

¥H

z{-

J +, |¦Mc§.}` z $¨ +332
hi0- ¥H,  32*VWX%-4=5YZ[

2+ 6\74%]9 ^
5 B, D$;R ou?,  $ A

CD9 )E*-+ F,0 +*ῌ+/ cm, E o #$-s&'(=>'. A, %!-(%!B$$%?, - + Fig. -b 0 A
C-

Fig. -d  _ . mm M4$N;R - 0 8

©ª«~ +0 mm +, +ῌ/+,mm O Cl f¬­log, $® mm 0$ 2h¯

9*B$ 7-` a:ab;ab<-Q D, E+* 

cd=ef$®°0]9 Fig. .  $ +±+,

!>g   !?@AB !J_3h- ²³´µ0^ 4 J#$H +3** m0nH
Table -.

Fig. ..

 (C-type) C ages for the “Kuroboku” soil samples.

Grain size cumulative curves for the blast deposit (F-type) (M-type)    
 (Mdf) 



5# M,-type:;<=>`FabNO%c  _deDEFG fFig. . Loc. .ῌ0g h9 Mdf-sf Cij fFig.

!"#$/g  kl +222 mnH opqrspt +32* mnH()*+,-.

uD'G9Hvw-x:;T= yHvT HvQ:2 45# M+-type, 6;T (!" fHoblitt et al., +32+ ; z{|{I ,**- ;%  &'
/0!"#$12 3

319

+.

7% . 78%9

Wholetz, ,**+ ; Yamamoto et al., +333g[\%9 P:(!"  ?@ABCD;T XHvw-x:;T K} ~~y:

EFG HIJ< A > C-type  K L C, E >;T HvQ:;T < $'G A

 M+-type  GMGNO1 HIJ`VHIJ<:;T Hvw-x:;T>

B, D > M,-type 78'G PQ< - RS:;AW XY<ZW

-< A%  PQ<:;T G 

ZW== s f7g #$1 h9 <:;T - RS#[\1  >]^_%AV HI

 PQ<[ ,f (. mm) ZW  TUGV F-typeHfk

320

Fig. /. Sorting (sf) vs. median diameter (Mdf) plots for the blast deposit. Small cross-marks represent the dataplots of the +222 blast deposit of Bandai (Yamamoto et al., +333 ; Kontani and Taniguchi, ,**-). The ﬁeldsof the pyroclastic ﬂow and pyroclastic fall are taken from Walker (+31+). The ﬁeld of the pyroclasitic surge
is drawn on the bases of the data plots of the +32* blast deposit of Mt. St. Helens and +222 blast deposit ofBandai volcano. Thick dot curves indicate the boundary of distinctive surge units recognized in the +32* blast
deposit of Mt. St. Helens (Hoblitt et al., +32+).





Fig. 0  !"#$ %& !'($!)*+ ,-./012345

Hoblitt et al, +32+ ; Sheridan and Wholetz, +32- ; Wholetz
and Sheridan, +313 6 789:;! 

 *+ Sandwave %&< Planar %&+=>?@AA4BCDE (Massive) ?F5 G*

HIJ!

$  K L J ? ! M  N D B, D D + Wholetz(,**+) *O5 Hydrovolcanic Fine Ash Beds PQRST*O5M;UD !VJ* KLJ!W+ Massive Bedforms XYD !VJ*Z4[4\34] Fig. 1^_`ab!cd$efg* h . ij!^?kl]mnoKL!p qrst]uvwx+ ST
!yPQRST*O5 z{ |}! ?F5~$0  !abB345  HIJ 0 Hydrovolcanic Fine Ash Beds
?F5~$+z{ |} ]  0!+}Fig. 0. Grain size distribution of the representative
blast deposits.

> ? +3** !r$»¼

321

Jd=, $eKLfMgWhi$3"
%&'( ,  Hydrovolcanic Fine Ash Beds
MB, D  Fig. .N  jk- FI4lCI$A=, 1Nm= noOf)+, DPQ$%&'( 
H + FI$A p2 M012N qRrS!:
4!5 sTt=5!,-.; $Uu.vwV;+,; x WX.AYW  H ,FI$I W! + ZN[\= <]ypz%
9[\{|=,; ^}~uw_g-+,-.A`W

 A  C-type a:

%;$D L:UrT $! b+5c$PQ%&'(Unodf$;+,.   [\eypz
 H - FI$fg2t=5!,-.; hij%&'(g-$;+,=! =;= k C L: B l= B, C g2rm7UnoOn
Fig. 1. The sf- Mdf characteristics of the blast
deposits in comparison with those of the surge
bedform types of Sheridan and Wohletz (+32-).

Eo  -.; 4 $<='.. PQ$%&'(= nodfGHg-=,.  O;pq$i H . FIr
s - FDt;'J( D'H$u<

 

W ,.AYH p2O%v=,; u Hydrovolcanic Fine Ash Beds  45=,.b  E CLno 

!"

 #

$%

&'( ) "* +,-.  /, 0wax=5!-. yL: D -.; qRSf$   1 %&'(23"PQ%&'(Dzfv=,. ! ) wet surge 4!5 (Wohletz,

{|  0 [\}e j$t(Waitt, +32+),**+) 678  1 -=5!,ypz,c

9!: ; /,<=5!"!

,W! + ] z=, - hi~$ N[\=I ,K-.L=,%&'( (wet surge) 
++ 



++ῌ+ 

>y
   ,K-w

? +3** ! 1 @ +1 " +0 ABC#,K?_ =,8X?

$ D +2 Aῌ+2 A%E - F$GH&!

¡/  /, :w .

, CI$C'J( - )!*+=  ::E a:¢;$&,K-.L=, MTable ,N£¤¥¦'§¨©ªb+,i$«¬­'®¯$EO / m P/= ,K0  MFig. 0N ° u4lwu

12QRS345T6UT789V W , --; ±²+5ª =, ³8 MyN :;<X$ / <Y=V 

 !%&'(  ys  ´µ¶-·¸

H C/C'O  MFig. . b-dN - 0D6 ,  P/

Z>[$F9U$J(\].

-.;   >¹=5?@ $A^BC._D :E!, %&'(!

º :%F`. PLaG.$ $bc - &'(PQ:../iu»=,

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³H¬­®¯8¸¹eº8°±²»8]³8"#´]8¼µB

322++ῌ,ῌ ῒΐῐ῔῎῍ῑ῏0V0 + F% (Taniguchi, +33-) 5678a)   

9:6;< +32* cdef|z"% }~




+*0 m- + +3**  

  

1.0

,.2

+*/ m- +*/ m- 

l7acdefz (Decker and Decker, +32+)=bwcxy?0 deS +32,+*+0 J  }~l7

fg+F.cdef  !"#

z (Brantley and Myers, ,***) =A B $% &'" ,.. km, ("wcxy?0 (Donn and Balachandran,

.῍+* cm  +32+) "% +*+1 J % 0,*** m-  )* +,-.

%

",0 RElCA6@

Qxy?cdef0 hnE >1

/0 12"# S mUVW +3**  1 scdef% 56

 34 56789:6;<  0** km,789:6;< +32* ij/Gk]

+*/ m-,.3 *., km- =
-km

< !>? +- km, *.*+

"#8@ABC6 +322 ; Siebert et al., +321 $DE " - F/G , F%

< +222 i;/Gj]

_31cdef$l% - "$lhnE

1"H I&'(JKL?Mc) !"8w mno

)NO*%/  P+/ % , . Q)Rpqbrs

H    < -.

OtS X+ +., m+.. m mG+/E/S , . Q)0M1 T2

4G8w+YZG O/+s 34%M15UV0x y (+ tu*.1- m, *.// m, *.+.῍*.- m

W67 X GYZ) E4 M1 8

Z 2 m<z+ ,./gῌcm[\1 "9: +E1 %;,,** kg0< ]s mGw%

9=+%>*

 ?@+AZ1 " ^+B> 9C
+G/_3
",`Z

Y? DE F.

GSG    , Ga.

+HL<

 

1 % M1IJ

0-b9E-.+/E _3

b) cdef Kg

R



L M

%h -** m+// m S/2i:j'h%OPcdef
CA6@Q3k l,0 <OP"1 RS"gT (Goto et al., ,**+) mUVW<1+3** Xn1 RS"g E  T2 oh ,/* m p-*OP
YZ q/r +233  2

cdef% +* J+.

s++ s"-

G {%VY

YZG |}/~"|zE  ,.1 mῌs " mcdef VY 1/* J  / 8{% PC · q · A C :TE8pi q : 8w A :w

" Q%8pi+ xV
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9:3 ;<ῌ ῏ ῎ ῍
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